日本が産油国になる日
アップロード日: 2011/02/17
石油の需要に供給が追いつかなくなり、価格が大幅に上昇する"ピークオイル"が間近に
従来有力とされてきた「ボトリオコッカス」と比べ、油を10倍以上の効率で作り出せる
日本を産油国、さらには輸出国にするまでの道筋、藻類に廃棄物、排水処理、CO2吸収
=========================================================
渡邉信
http://ja.wikipedia.org/wiki/%E6%B8%A1%E9%82%89%E4%BF%A1
渡邉 信（わたなべ まこと、Makoto M Watanabe、1948年3月5日 - ）は日本の藻類学者。筑波大学大学院教授。東南アジア淡水系およびシャジクモ類の保全生態学や、アオコなど有毒藍藻の研究で知られる。近年は藻類オイル（en:Algae fuel）の研究に携わっており、2010年には炭化水素生産効率の高い従属栄養性藻類であるオーランチオキトリウムに関する研究を発表した。
略歴
1948年3月5日 - 宮城県に生まれる[1]。
1971年 - 東北大学理学部生物学科卒業。
1977年 - 北海道大学大学院理学研究科博士課程修了。理学博士 論文の題は「Biosystematics in closterium of sexual unicellular areen algae and calothrix and spirulina of asexual filamentous blue-green algae with special reference to the analyses of natural populations(有性単細胞緑藻ミカヅキモと無性糸状藍藻,ヒゲモ,ラセンモの種分類学的研究 : 特に自然集団の解析と関連して) 」[2]。
1978年 - 富山大学薬学部助手、国立公害研究所水質土壌環境部研究員に就任。
1990年 - 国立環境研究所生物圏環境部環境微生物研究室長に就任。
1991年 - 国際藻類学会パーペンフス賞受賞。
1997年 - 国立環境研究所生物圏環境部長に就任。
2006年 - 筑波大学大学院生命環境科学研究科教授に就任。
2007年 - 日本微生物資源学会学会賞受賞[3]。
2010年 - オーランチオキトリウムに関する研究結果を発表[4]。
外部リンク
環境・生物多様性研究室 - 筑波大学大学院生命環境科学研究科
渡辺信 - 研究開発支援総合ディレクトリ（ReaD）
最終更新 2013年4月28日
=========================================================
TBS「夢の扉＋」5月29日 #8「藻から石油！奇跡のエネルギー革命！」
アップロード日: 2011/05/27
=========================================================
「藻類バイオマス」実験施設 つくば市に完成
It is completed in "alga biomass" experiment facilities Tsukuba-City
公開日: 2014/03/24
=========================================================
人類の未来を拓く藻類エネルギー #1（渡邉 信 氏）
アップロード日: 2010/08/03
人類の未来を拓く藻類エネルギー #2（渡邉 信 氏）
=========================================================
オーランチオキトリウム
http://ja.wikipedia.org/wiki/%E3%82%AA%E3%83%BC%E3%83%A9%E3%83%B3%E3%83%81%E3%82%AA%E3%82%AD%E3%83%88%E3%83%AA%E3%82%A6%E3%83%A0
オーランチオキトリウム（学名：Aurantiochytrium）とは、水中の有機物上に、小さな細胞集団を作る微生物。無色ストラメノパイルであるラビリンチュラの1種である。炭化水素を高効率で生成・蓄積する株が日本の研究者によって発見され、石油の代替燃料を生産できる「石油を作る藻類」として注目されている[1][2][3]。
特徴
他のラビリンチュラと同様、葉緑体を持たず光合成をしない従属栄養生物であり、周囲の有機物を吸収して生育する[4]。本属は熱帯から亜熱帯域にかけてのマングローブ林や河口域など、海水と淡水の入り混じる汽水域を好む[5]。
細胞は球形で直径5-数十μm程度、細胞壁は薄い。増殖は基本的に二分裂による。分裂した細胞がそのまま連結し続けることで小型の群体を形成する。遊走子は2本の不等長の鞭毛を持つ。ラビリンチュラ類の特徴である細胞外細胞質のネットワークはあまり発達しない[6]。
細胞はオレンジ色に呈色する場合があるが、これは細胞内に含まれるアスタキサンチン、フェニコキサンチン、カンタキサンチン、βカロテンなどの種々のカロテノイドによる。このオレンジ色（aurantius; ラテン語 "橙黄色の"）が属名の由来である[7]。他にアラキドン酸、ドコサヘキサエン酸などの不飽和脂肪酸（高度不飽和脂肪酸、Poly-unsaturated fatty acid; PUFA）が含まれる[6][4]。
炭化水素の生産
本属を含むラビリンチュラ類が PUFA を蓄積することは以前より知られていた。[4]筑波大学教授の渡邉信らのグループよって、高効率で炭化水素（スクアレン）を産生し細胞内に溜め込む株が沖縄のマングローブ林にて、水中の落葉表面から発見された[8]。
炭化水素を作り出す藻類は他にも知られていたが、油の回収や処理を含む生産コストが1リットルあたり800円程度かかるのが難点だった。オーランチオキトリウムを利用することで、その10分の1以下のコストで生産できると期待されている[3]。
これまで有望とされていた緑藻類のボツリオコッカス・ブラウニーと同じ温度条件で培養した場合、10-12倍の量の炭化水素が得られる。培養することで、1リットルあたり1グラムのスクアレンを3日で作り出すことができ、仮に深さ1mの水槽で培養したとすると、面積1ヘクタールあたり年間最大約1万トンの炭化水素を作り出せると試算されている。これは2万ヘクタールの培養面積で日本の年間石油消費量を賄える量であり、耕作放棄地（38.6万ヘクタール）などを利用した生産が考えられている[1]。
火力発電に使用する場合は、精製を行なうことなく、培養したものをペレットにしたものが使用できる。
渡邉信・彼谷邦光らの筑波大研究チームでは、生活排水中の有機物を食べさせる実験や、二酸化炭素をボトリオコッカスに食べさせ、出てきた余剰有機物をオーランチオキトリウムの餌に使う実験も行っている。日本で必要とされる量を賄う規模で培養するとなると、計算上では餌となる有機物が足りないため、イモや藻類由来のデンプンや生ごみを利用する計画もある[8]。
発見と実用化に向けた取り組み
2010年12月14日 - 筑波大学教授の渡邉信らのグループが、特に高効率で化石燃料の重油に相当する炭化水素（スクアレン）を産生し細胞内に溜め込む株を発見し、茨城県つくば市で開催された藻類の国際学会 "Asia Oceania Algae Innovation Summit" で報告した[1][9]。
従来有力とされてきた「ボトリオコッカス」と比べ、油を10倍以上の効率で作り出せる
日本を産油国、さらには輸出国にするまでの道筋、藻類に廃棄物、排水処理、CO2吸収
=========================================================
渡邉信
http://ja.wikipedia.org/wiki/%E6%B8%A1%E9%82%89%E4%BF%A1
渡邉 信（わたなべ まこと、Makoto M Watanabe、1948年3月5日 - ）は日本の藻類学者。筑波大学大学院教授。東南アジア淡水系およびシャジクモ類の保全生態学や、アオコなど有毒藍藻の研究で知られる。近年は藻類オイル（en:Algae fuel）の研究に携わっており、2010年には炭化水素生産効率の高い従属栄養性藻類であるオーランチオキトリウムに関する研究を発表した。
略歴
1948年3月5日 - 宮城県に生まれる[1]。
1971年 - 東北大学理学部生物学科卒業。
1977年 - 北海道大学大学院理学研究科博士課程修了。理学博士 論文の題は「Biosystematics in closterium of sexual unicellular areen algae and calothrix and spirulina of asexual filamentous blue-green algae with special reference to the analyses of natural populations(有性単細胞緑藻ミカヅキモと無性糸状藍藻,ヒゲモ,ラセンモの種分類学的研究 : 特に自然集団の解析と関連して) 」[2]。
1978年 - 富山大学薬学部助手、国立公害研究所水質土壌環境部研究員に就任。
1990年 - 国立環境研究所生物圏環境部環境微生物研究室長に就任。
1991年 - 国際藻類学会パーペンフス賞受賞。
1997年 - 国立環境研究所生物圏環境部長に就任。
2006年 - 筑波大学大学院生命環境科学研究科教授に就任。
2007年 - 日本微生物資源学会学会賞受賞[3]。
2010年 - オーランチオキトリウムに関する研究結果を発表[4]。
外部リンク
環境・生物多様性研究室 - 筑波大学大学院生命環境科学研究科
渡辺信 - 研究開発支援総合ディレクトリ（ReaD）
最終更新 2013年4月28日
=========================================================
TBS「夢の扉＋」5月29日 #8「藻から石油！奇跡のエネルギー革命！」
アップロード日: 2011/05/27
=========================================================
「藻類バイオマス」実験施設 つくば市に完成
It is completed in "alga biomass" experiment facilities Tsukuba-City
公開日: 2014/03/24
つくば国際戦略総合特区のプロジェクトの一つで、藻から燃料油を作り出す「藻類バイオ
施設は、特区制度の活用で農地法の規制を緩和し、同大近くの農地に約２億円投じて整備
ボトリオコッカスは光合成により重油の主成分である炭化水素を作り出す性質があり、石
ディーゼル車を使ったデモ走行は同大内の公道などを使い、約５ｷﾛの距離で実施。軽油
本格的な走行実験は来年度から実施し、排ガス濃度などのデータを収集しながら、年間延
同大によると、藻類燃料は現在１ﾘｯﾄﾙ当たり約千円以上と生産コストが高い。同大で
研究チームの渡辺信同大教授は「２０２０年をめどに、バイオ燃料を使う時代がやってく
２０１１年12月に指定されたつくば国際戦略総合特区ではこのほか▽「ホウ素中性子捕
次世代がん治療は、東海村白方の「いばらき中性子医療研究センター」で中性子ビーム加
医療用ロボットの実用化では、筑波大のベンチャー企業サイバーダインが製造するロボッ
施設は、特区制度の活用で農地法の規制を緩和し、同大近くの農地に約２億円投じて整備
ボトリオコッカスは光合成により重油の主成分である炭化水素を作り出す性質があり、石
ディーゼル車を使ったデモ走行は同大内の公道などを使い、約５ｷﾛの距離で実施。軽油
本格的な走行実験は来年度から実施し、排ガス濃度などのデータを収集しながら、年間延
同大によると、藻類燃料は現在１ﾘｯﾄﾙ当たり約千円以上と生産コストが高い。同大で
研究チームの渡辺信同大教授は「２０２０年をめどに、バイオ燃料を使う時代がやってく
２０１１年12月に指定されたつくば国際戦略総合特区ではこのほか▽「ホウ素中性子捕
次世代がん治療は、東海村白方の「いばらき中性子医療研究センター」で中性子ビーム加
医療用ロボットの実用化では、筑波大のベンチャー企業サイバーダインが製造するロボッ
人類の未来を拓く藻類エネルギー #1（渡邉 信 氏）
アップロード日: 2010/08/03
シンポジウム「近未来への招待状 ～ナイスステップな研究者2009からのメッセージ～」（2010年4月22日(木)
渡邉 信 氏（筑波大学大学院生命環境科学研究科 教授）の講演です。
※肩書き・役職は講演当時のものです
渡邉 信 氏（筑波大学大学院生命環境科学研究科 教授）の講演です。
※肩書き・役職は講演当時のものです
人類の未来を拓く藻類エネルギー #2（渡邉 信 氏）
=========================================================
オーランチオキトリウム
http://ja.wikipedia.org/wiki/%E3%82%AA%E3%83%BC%E3%83%A9%E3%83%B3%E3%83%81%E3%82%AA%E3%82%AD%E3%83%88%E3%83%AA%E3%82%A6%E3%83%A0
オーランチオキトリウム（学名：Aurantiochytrium）とは、水中の有機物上に、小さな細胞集団を作る微生物。無色ストラメノパイルであるラビリンチュラの1種である。炭化水素を高効率で生成・蓄積する株が日本の研究者によって発見され、石油の代替燃料を生産できる「石油を作る藻類」として注目されている[1][2][3]。
特徴
他のラビリンチュラと同様、葉緑体を持たず光合成をしない従属栄養生物であり、周囲の有機物を吸収して生育する[4]。本属は熱帯から亜熱帯域にかけてのマングローブ林や河口域など、海水と淡水の入り混じる汽水域を好む[5]。
細胞は球形で直径5-数十μm程度、細胞壁は薄い。増殖は基本的に二分裂による。分裂した細胞がそのまま連結し続けることで小型の群体を形成する。遊走子は2本の不等長の鞭毛を持つ。ラビリンチュラ類の特徴である細胞外細胞質のネットワークはあまり発達しない[6]。
細胞はオレンジ色に呈色する場合があるが、これは細胞内に含まれるアスタキサンチン、フェニコキサンチン、カンタキサンチン、βカロテンなどの種々のカロテノイドによる。このオレンジ色（aurantius; ラテン語 "橙黄色の"）が属名の由来である[7]。他にアラキドン酸、ドコサヘキサエン酸などの不飽和脂肪酸（高度不飽和脂肪酸、Poly-unsaturated fatty acid; PUFA）が含まれる[6][4]。
炭化水素の生産
本属を含むラビリンチュラ類が PUFA を蓄積することは以前より知られていた。[4]筑波大学教授の渡邉信らのグループよって、高効率で炭化水素（スクアレン）を産生し細胞内に溜め込む株が沖縄のマングローブ林にて、水中の落葉表面から発見された[8]。
炭化水素を作り出す藻類は他にも知られていたが、油の回収や処理を含む生産コストが1リットルあたり800円程度かかるのが難点だった。オーランチオキトリウムを利用することで、その10分の1以下のコストで生産できると期待されている[3]。
これまで有望とされていた緑藻類のボツリオコッカス・ブラウニーと同じ温度条件で培養した場合、10-12倍の量の炭化水素が得られる。培養することで、1リットルあたり1グラムのスクアレンを3日で作り出すことができ、仮に深さ1mの水槽で培養したとすると、面積1ヘクタールあたり年間最大約1万トンの炭化水素を作り出せると試算されている。これは2万ヘクタールの培養面積で日本の年間石油消費量を賄える量であり、耕作放棄地（38.6万ヘクタール）などを利用した生産が考えられている[1]。
火力発電に使用する場合は、精製を行なうことなく、培養したものをペレットにしたものが使用できる。
渡邉信・彼谷邦光らの筑波大研究チームでは、生活排水中の有機物を食べさせる実験や、二酸化炭素をボトリオコッカスに食べさせ、出てきた余剰有機物をオーランチオキトリウムの餌に使う実験も行っている。日本で必要とされる量を賄う規模で培養するとなると、計算上では餌となる有機物が足りないため、イモや藻類由来のデンプンや生ごみを利用する計画もある[8]。
発見と実用化に向けた取り組み
2010年12月14日 - 筑波大学教授の渡邉信らのグループが、特に高効率で化石燃料の重油に相当する炭化水素（スクアレン）を産生し細胞内に溜め込む株を発見し、茨城県つくば市で開催された藻類の国際学会 "Asia Oceania Algae Innovation Summit" で報告した[1][9]。
- 2011年度 - 仙台市・筑波大学・東北大学は共同で、オーランチオキトリウムを増殖する実証実験を始める予定となっている。早ければ同年内に仙台市に実証プラントを建設し、宮城野区の下水処理施設「南蒲生浄化センター」の生活・産業排水を利用して、3〜4年かけて研究開発が行われる[10][11][12]。
- 2011年12月 - 渡邉信教授の研究チームと自動車メーカーのマツダが共同でオーランチオキトリウムから精製した油を軽油に70%混ぜて、クリーンディーゼル車（CX-5）を走らせる実験を行い成功した[13]。
- 2013年4月 - 筑波大学と東北大学の共同研究施設が、仙台市南蒲生浄化センターに開所[14][15][16]。2011年11月、筑波大学が「藻類の生産技術確立」、東北大学が「オイル抽出・生成技術確立」、仙台市が「下水処理施設を中心とした協力」という役割分担で結ばれた協定による施設である[16]。
オーランチオキトリウム属は、2007年に本多らによってシゾキトリウム属 Schizochytrium から分離・再編されてできた属である[17]。そのため特許文献などでは、（2007年以降も）「シゾキトリウム」と表記されている場合も多い[4]。
属レベルの分類は、分子系統解析、脂肪酸およびカロテノイド組成、光学顕微鏡レベルの形態観察に基づいて行われている[18]。種レベルでは生活環の違いに基づいて分類されている（下記）が、この2種の他にも多数の未分類種が株番号で識別されたまま研究に用いられている[17]。
- Aurantiochytrium limacinum
- 本属のタイプ種。細胞直径7-15μm、遊走子嚢では最大24μm。遊走子嚢中では16-64個の遊走子が形成される。本種はナメクジ型 (limaciform) の不定形の細胞を生じる場合がある[18]。
- Aurantiochytrium mangrovei
- A. limacinum とは異なり、遊走子嚢を形成しない。通常の細胞が二分裂を繰り返して遊走子を生じる[18]。
なお、シゾキトリウムは元来は遊走細胞の特徴から卵菌類と見なされていた[20]。その後シゾキトリウムを含むヤブレツボカビ科は、表在性の胞子嚢を形成するという特徴から粘菌類に移された[21]。ラビリンチュラに近縁であると考えられるようになったのは、仮足状に伸びる構造がラビリンチュラの細胞外細胞質と相同であるとみなされるようになったからである[22]。その後、ラビリンチュラ類は真菌類と系統を異にすること、褐藻や珪藻など多くの藻類を擁するストラメノパイルに属することが明らかとなった。このような系統的位置に基づき、オーランチオキトリウムは「従属栄養性藻類」と表現されることもある[23]が、それによって｢光合成をするのだ｣との誤解を招くことも起きている。
最終更新 2013年12月19日
=========================================================
藻から石油をつくる …オーランチオキトリウム
http://tamrhyouka.hiho.jp/gijyutu-mokarasekiyu.html
2010.12月に、日本の筑波大学から藻から石油をつくる…というニュースが発表された。
すぐにニュースから消されたが、これは国際的に衝撃が大きすぎる内容だからだろう。
話は違うが、中東付近で笑い話があるのだとか。
クウェートの国民が、日本人を恐れているのだそうだ。それは、日本の技術力が、石油の代替品を作って、クウェートの産油国としての地位を脅かすのではないか…と。
→その笑い話が、ちっとも笑い話ではなくなったようだ。
その位、国際社会への影響の大きな技術ということであろう。
冒頭の発表があって半年を経過し、国会とかテレビとかでぼつぼつ出始めた。
□2010.12月の新聞記事から、見直してみよう。
★生産能力１０倍 「石油」つくる藻類、日本で有望株発見 ・藻類に「石油」を作らせる研究で、筑波大のチームが従来より１０倍以上も油の生産能力が 高いタイプを沖縄の海で発見した。
チームは工業利用に向けて特許を申請している。
将来は燃料油としての利用が期待され、資源小国の日本にとって朗報となりそうだ。
茨城県で開かれた国際会議で１４日に発表した。
筑波大の渡邉信教授、彼谷邦光特任教授らの研究チーム。
海水や泥の中などにすむ「オーランチオキトリウム」という単細胞の藻類に注目し、東京湾やベトナムの海などで計１５０株を採った。
これらの性質を調べたところ、沖縄の海で採れた株が極めて高い油の生産能力を持つことが分かった。
球形で直径は５～１５マイクロメートル（マイクロは１００万分の１）。
水中の有機物をもとに化石燃料の重油に相当する炭化水素を作り、細胞内にため込む性質がある。
同じ温度条件で培養すると、これまで有望だとされていた藻類のボトリオコッカスに比べて、１０～１２倍の量の炭化水素を作ることが分かった。
研究チームの試算では、深さ１メートルのプールで培養すれば面積１ヘクタールあたり年間約１万トン作り出せる。
「国内の耕作放棄地などを利用して生産施設を約２万ヘクタールにすれば、日本の石油輸入量に匹敵する生産量になる」としている。
炭化水素をつくる藻類は複数の種類が知られているが生産効率の低さが課題だった。
渡邉教授は「大規模なプラントで大量培養すれば、自動車の燃料用に１リットル ５０円以下で供給できるようになるだろう」と話している。
また、この藻類は水中の有機物を吸収して増殖するため、生活排水などを浄化しながら油を生産するプラントをつくる一石二鳥の構想もある。
（画像は、オーランチオキトリウムを培養しているところ）
□さて、この藻の名前を「オーランチオキトリウム」というのだが、これを発見した経緯、培養方法等が、別のニュース源に書いてあったのでご紹介したい。
なお、答えているのは、筑波大学の渡邊信教授。
□答え。
今回のオーランチオキトリウムは、オイルの生成量でいえばボトリオコッカスの3分の1ですが、増殖スピードが36倍と速いのが特長です。
生産効率は従来に比べて単純計算で12倍になるわけです。
問い このような株を採取できたのは、どうしてでしょう？
□答え。
宝くじのように、たまたまそういう株を引き当てたと思っていらっしゃる方もいますね（笑）。
それが科学と言えるのかと。
しかし、闇雲にあちこちから採取すれば、よい株が採れるとは限りません。
私たちも幸運を引き当てるために、周到な準備をしました。
藻類に関する論文を相当数調べたところ、オーランチオキトリウムの仲間がオイルを作るという報告がありました。
それこそ乾燥重量で0.1％程度と極めて少ないながらも、先述のスクアレンを作るものがいるというのです。
そこで、論文から場所の当たりを付けて日本近海で150株採取したところ、今回の株が見つかったというわけです。
勝率の低い賭でしたが、何とか当たりを引くことができました。
株が見つかるまでに1年半かかりましたが、これは随分早い方でしょう。
遺伝子組換えや品種改良だと、10年や20年かかったかもしれません。
探索という手段には、これだけのスピードがあります。
問い─オイル生産効率の高いオーランチオキトリウムが採取されたことで、バイオ燃料の研究も一気に弾みが付きそうですね。生産効率やコストはどれくらいでしょう？
光合成する藻類とは培養の仕方もまったく変わってくると思いますが。
□答え…その辺の話は、まだ先の段階ですね。
光合成の藻類を使うにせよ従属栄養藻類にせよ、まだ研究室レベルのデータを元に推測しているに過ぎず、実規模でのデータがないのです。
これまではどんなにラフに計算をしたとしても、コスト的に絶対に実用化できませんでした。
そこに高い潜在能力を持ったオーランチオキトリウムが見つかり、実用化できる可能性が見えてきたということです。
□答え…
有機物を含んだ排水、有機排水が家庭や工場から大量に出てきます。
これをオーランチオキトリウムのエサとして利用しようというのが、私の考えです。
現在、下水等の有機排水を処理するためには、最初に固形物を沈殿させ、その後の一次処理水に活性汚泥というバクテリアの塊を投入しています。
一次処理水には有機物が多く含まれていますから、活性汚泥の代わりにオーランチオキトリウムを投入すれば、オーランチオキトリウムが排水中の有機物をエサとして炭化水素を作ることになります。
オーランチオキトリウムが処理した後の二次処理水には、窒素とリンが大量に残っていますから、この二次処理水にボトリオコッカスを投入し、やはり炭化水素を作らせます。
炭化水素を抽出した後のオーランチオキトリウムやボトリオコッカスは、動物の飼料やメタン発酵に利用できるでしょう。
問い-藻はどのように培養するのでしょう？
□答え…
光合成をしないオーランチオキトリウムの場合は、地下に閉鎖系の培養環境を作るのがよいでしょう。
地下なら冬場でも15-20℃くらいで水温は安定しており、15℃なら6時間、20℃なら4時間で倍に増えます。
オーランチオキトリウムには光を当てる必要がないため、広い面積が必要ありません。
工場のすぐ横にオーランチオキトリウムの培養タンクを設置して、工場の排熱を利用するといった方法も使えそうです。
現在、発酵微生物で使われているノウハウや設備をそのまま流用できますから、研究は加速度的に進むのではないでしょうか。
光合成するボトリオコッカスの場合は、休耕田のような開放系で培養するか、人工的に光を当てる閉鎖系で培養することになります。
開放系はコストが少なくて済むというメリットの反面、他の微生物が混入するなど環境制御が難しいという問題点があります。
一方の閉鎖系は、環境制御が簡単ですがコストがかかります。
開放系のデメリットは、特殊な環境で生きるように藻を品種改良することで解決できるかもしれません。
例えば、塩分濃度が海水の2倍という環境で生きられるようにすれば、他の微生物の混入を防げるでしょう。
閉鎖系に関しても、使い捨てのソフトプラスチックバッグを使ってコストを下げる方法が研究されています。
問い─アメリカは新しい技術に対する投資の仕方が大胆ですよね。100のベンチャーにまとめて投資して、そのうち1つが大成功すればいいという。
□答え…
そういうやり方でいいんです。
世界で消費されている原油が50億トン、1リットル当たり50円としたら、250兆円の市場がすでに存在するわけです。
バイオ燃料は、ものすごくリターンの大きい世界なんですよ。
それは日本が産油国になるということだけではありません。
世界のパワーバランスすら変える可能性を秘めています。
問い─エネルギー資源が特定の地域、国に偏るのではなく、遍在するということですね。
□答え…
そういうことです。
技術さえあれば、誰もがエネルギーを手に入れられるようになります。
私は、エネルギーが潤沢になることで、世界が抱える問題のかなりの部分を解決できるのではないかと考えています。
人類をエネルギー資源の制約から解放する、これこそが、全人類が待ち望んでいるイノベーションではないでしょうか？
□最後にこの渡邊先生の風貌を。
□まとめ、感想など
記事の内容は実験室レベルでの話であるから、工業化する、大規模化するなかで、多くの特許を生み出そう。
でも、日本人なりゃこそのペースでことが進んでいるようだ。
渡邊先生は、エネルギーフリーの時代がくる…と言われる。
少なくとも、安価に自国が使用する液体燃料は、自国で生産できる時代がくる…ということだ。
人類に夢を持たせてくれる技術だと言えよう。
■2011.8.16
新聞に以下の記事が載っていた。
□まとめ、感想など
記事を読んで、本命の「オーランチオキトリウム」でか…と一瞬思った。
が、読んでいると、本命の前のポトリオコッカスでの実験のようだ。
場所がアメリカであり、まず、ポトリオコッカスで大量生産の技術を開発して、それから本命の「オーランチオキトリウム」でということであろう。
また、実験場もたぶん日本に作ることになろう。
それこそ、中東の産油国の地位を転覆しかねない程の技術だ。
用心に用心を重ねているようだ。
しかし、ここでdic が一歩先んじて、このプロジェクトに参加したことになる。本命のオーランチオキトリウムの場合も、dic が優先しそうだなぁ。
=========================================================
石油を作り出す全く新しい方法
公開日: 2013/10/10
新仮説ファイル ON AIR 2002/5/5
アナログデータの保存状態が悪く、画像・音声に乱れがありますがご了承ください。
=========================================================
相良油田
http://ja.wikipedia.org/wiki/%E7%9B%B8%E8%89%AF%E6%B2%B9%E7%94%B0
相良油田（さがらゆでん）は、静岡県榛原郡菅山村（現在の牧之原市西部）にあった油田。日本では太平洋岸唯一の産油地だったが、産油量の激減や、日本国外からの安い原油の輸入などのため、1955年に廃止になった。世界的にも希な軽質油で、精製せずにそのままで自動車が動くほどだった。
相良油田は、1872年（明治5年）に海老江の谷間で油くさい水が出ることと聞いた元徳川藩士の村上正局（まさちか）によって発見されことに始まる[1]。1873年（明治6年）5月には手掘りにより採油が始まった。1874年（明治7年）には日本石油（現：JX日鉱日石エネルギー）の前身である長野石炭油会社によって日本で最初の機械掘りが行われた。最盛期の1884年（明治17年）頃は、約600人が働き、年間721キロリットルが産出されていた。採油を停止したのちの1980年（昭和55年）11月28日には静岡県指定文化財（天然記念物）となり、今では「油田の里公園」として周辺が整備されている。
1993年、京都大学大学院の今中忠行（現在：立命館大学生命科学部）は研究室内の「無酸素実験装置」において、 相良油田から採取した石油分解菌「Oleomonas sagaranensis HD-1株」が通常状態では石油を分解する能力を持ちながら、 石油も酸素も無い環境におかれると、細胞内に逆に原油を作り出すことを発見した。今中忠行らはこの石油分解菌がメタンハイドレートに関係していると指摘した。
ガソリン34% 灯油34% 軽油22.5% 重油9.5% 非常に軽質であり低粘度、ウイスキーやブランデーのような透き通った色の液体である
現在では観光と研究用に残されている油田にて数年に一度の採掘試験を行っており、この模様はイベントとして一般に公開されている。この際に汲みたての原油からゴミを濾紙にて濾しただけの精製前原油を使い原動機付自転車などのガソリンエンジンや農業用発動機の始動実演が行われている。
外部リンク
アナログデータの保存状態が悪く、画像・音声に乱れがありますがご了承ください。
=========================================================
相良油田
http://ja.wikipedia.org/wiki/%E7%9B%B8%E8%89%AF%E6%B2%B9%E7%94%B0
相良油田（さがらゆでん）は、静岡県榛原郡菅山村（現在の牧之原市西部）にあった油田。日本では太平洋岸唯一の産油地だったが、産油量の激減や、日本国外からの安い原油の輸入などのため、1955年に廃止になった。世界的にも希な軽質油で、精製せずにそのままで自動車が動くほどだった。
相良油田は、1872年（明治5年）に海老江の谷間で油くさい水が出ることと聞いた元徳川藩士の村上正局（まさちか）によって発見されことに始まる[1]。1873年（明治6年）5月には手掘りにより採油が始まった。1874年（明治7年）には日本石油（現：JX日鉱日石エネルギー）の前身である長野石炭油会社によって日本で最初の機械掘りが行われた。最盛期の1884年（明治17年）頃は、約600人が働き、年間721キロリットルが産出されていた。採油を停止したのちの1980年（昭和55年）11月28日には静岡県指定文化財（天然記念物）となり、今では「油田の里公園」として周辺が整備されている。
1993年、京都大学大学院の今中忠行（現在：立命館大学生命科学部）は研究室内の「無酸素実験装置」において、 相良油田から採取した石油分解菌「Oleomonas sagaranensis HD-1株」が通常状態では石油を分解する能力を持ちながら、 石油も酸素も無い環境におかれると、細胞内に逆に原油を作り出すことを発見した。今中忠行らはこの石油分解菌がメタンハイドレートに関係していると指摘した。
ガソリン34% 灯油34% 軽油22.5% 重油9.5% 非常に軽質であり低粘度、ウイスキーやブランデーのような透き通った色の液体である
現在では観光と研究用に残されている油田にて数年に一度の採掘試験を行っており、この模様はイベントとして一般に公開されている。この際に汲みたての原油からゴミを濾紙にて濾しただけの精製前原油を使い原動機付自転車などのガソリンエンジンや農業用発動機の始動実演が行われている。
外部リンク
相良油田坑見学 相良油田の里公園(牧之原市観光協会サイト)
最終更新 2013年5月18日
=========================================================
オレオモナス・サガラネンシス
http://ja.wikipedia.org/wiki/%E3%82%AA%E3%83%AC%E3%82%AA%E3%83%A2%E3%83%8A%E3%82%B9%E3%83%BB%E3%82%B5%E3%82%AC%E3%83%A9%E3%83%8D%E3%83%B3%E3%82%B7%E3%82%B9
オレオモナス・サガラネンシス（Oleomonas sagaranensis）は、グラム陰性嫌気性の石油生成・分解細菌で、静岡県の相良油田から発見された。
1993年、京都大学大学院の今中忠行（現在：立命館大学生命科学部）らは、相良油田から採取・単離した菌株「HD-1株」が通常状態では石油を分解する能力を持ちながら、石油も酸素もない環境におかれると細胞内に逆に原油を作り出すことを発見、新属新種であるとして2002年に命名・報告した[2]。今中らは本種がメタンハイドレートに関係しているとも指摘した。
「石油#石油分解菌説」も参照
外部リンク
講演記録 今中忠行「極限微生物は面白い」(PDF)2008年12月26日 第3回中部大学ライフサイエンスフォーラム pp.16-17
北海道大学森川正章研究室：油田細菌
森川正章 「細菌によるバイオサーファクタント生産と石油代謝に関する研究」(PDF) 1994-08 pp.69-102
金森武 「新属新種細菌Oleomonas sagaranensisの同定及び細菌における新規尿素資化経路に関する研究」 2004-11-24
最終更新 2014年2月7日
=========================================================
極限微生物は面白い
今中 忠行
http://stu.isc.chubu.ac.jp/bio/public/ann_rep_res_inst_biol_funct/annual-report_v9_2009/pdf/003.pdf
=========================================================
超好熱菌による廃棄バイオマスからの連続水素生産
Continuous Hydrogen Production by the Hyperthermophile Thermococcus kodakaraensis KOD1
今中 忠行
http://www.jseb.jp/jeb/09-02/09-02-065.pdf
=========================================================
「深度地下極限環境微生物の探索と利用」
京都大学大学院工学研究科 教授
今中 忠行
http://www.jst.go.jp/kisoken/crest/report/sh_heisei9/pdf/05_kyokugen/kyokugen-03.pdf
－377－
１．研究実施の概要
研究目的
本研究では未開拓の深度地下極限環境から新規な微生物を分離し、それらが有するであろう特殊酵素、代謝系や環境適応戦略を解析していくことを目標に設定している。これにより地下微生物生態系の解明、生命進化過程の理解に加えて、遺伝子資源の確保、工業的利用や環境改善へ貢献できることを期待している。
研究成果概要
1）新規極限環境微生物の分離と同定（京都大学大学院工学研究科合成・生物化学専攻）
・極低温でも生育するSN16A 株、KB700A 株
我々は国内の地下土壌サンプルから低温でも生育できる新規微生物を複数分離した。比較的浅い地下環境から分離したSN16A 株は-５℃から37℃の温度範囲で生育し、新属新種の微生物である可能性が示唆された。また、KB700A 株は地下700m の水サンプルから分離され、-10℃という生物にとって極限的な低温でも増殖することを見いだした。KB700A株からはさらに低温領域で高活性を示すlipase が同定・解析された。
・海底油田より分離したM4 株、MAL1 株
マレーシア沖海底油田（海抜-5000m）より地下微生物M4 株、MAL1 株を分離した。嫌気条件下ではM4 株は硝酸イオンを最終電子受容体とし、窒素を発生する脱窒菌であることが判った。
・石油分解合成菌Oleomonas sagaranensis HD-1 株
我々は静岡県相良油田より様々な直鎖状炭化水素や芳香族化合物を効率よく分解する細菌HD-1 株を分離した。また、水素をエネルギー源、二酸化炭素を炭素源として培養した場合にHD-1 株の菌体内に炭化水素の蓄積を認めた。このような特性を有する微生物はい
KB700A 株 HD-1 株
KOD1 株
MAL1 株
VA1 株
SN16A 株
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ままでに報告例はなく、HD-1 株内に様々な新規代謝系が存在すると考えられる。遺伝子解析によりHD-1 株はα-Proteobacteria に属する親族新種の微生物であることが判明し、
Oleomonas sagaranensis HD-1 株と命名された。
・超好熱始原菌Thermococcus kodakaraensis KOD1 株
我々は鹿児島県小宝島の硫気孔より超好熱始原菌Thermococcus kodakaraensis KOD1 株を分離した。本菌は65℃～100℃という高温で生育する絶対嫌気性菌であり、硫黄呼吸や発酵を行って、アミノ酸や多糖類を分解・資化する。また、16S rRNA の比較により、KOD1株は進化系統樹の根の近いところに位置する極めて単純な生命体であることが示唆された。
・好気性超好熱始原菌Pyrobaculum calidifontis VA1 株
KOD1 株を含め、超好熱菌のほとんどは絶対嫌気性菌であるが、我々はフィリピンの温泉より好気条件下で生育する超好熱菌VA1 株を分離した。VA1 株は約１μmの桿菌であり、大気条件下で温度90～95℃、pH7.0 で最も良好な生育を示した。また嫌気条件下では、超好熱菌には珍しく硫黄呼吸ではなく硝酸呼吸を行っていることが判った。系統解析の結果、VA1 株はPyrobaculum 属に近縁でありながら、既存の菌種とは異なることが判明し、本菌をPyrobaculum calidifontis VA1 株と命名した。VA1 株より、超耐熱性を示すcatalase およびcarboxylesterase などの有用酵素が同定・解析された。
2）耐熱性酵素の成熟化には高温環境が必要
我々はKOD1 株のglutamate dehydrogenase（GDH）の研究を通じて、超好熱菌由来タンパク質に普遍的な特性を発見した。すなわち、常温菌由来のタンパク質は一般に熱変性するのに対し、超好熱菌由来の組換えタンパク質は熱により成熟していくことを明らかにした。KOD1 株内の高温環境で合成されたGDH は６量体構造を有し、高い比活性を示す。
一方、GDH 遺伝子を大腸菌を宿主として発現させた場合では、天然型のGDH と比べて酵素活性が低く、構造の異なる単量体タンパク質が得られた。そこで70℃、20min の熱処理を施すと組換え型GDH は比活性、立体構造ともに天然型のGDH に近づくことが明らかとなった。また、一度熱処理を行うことにより、本酵素は低温域でも天然型GDH と類似した挙動を示した。このような特徴はGDH のみならず、我々が解析した超好熱菌由来酵素の全てについて認められた。以上のことから、耐熱性タンパク質の成熟化には熱が重要であり、それは熱による酵素タンパク質の不可逆な構造変換に起因することが判明した。
3）新しい構造や機能特性を有する酵素の発見
Rubisco は全ての植物・藻類・藍藻に存在し、二酸化炭素を有機物に固定する重要な役割を担っている。Rubisco は地球上で最も多量に存在する酵素であり、本酵素の改良は地球温暖化や食糧問題の解決に大きく貢献すると期待されている。Tk-Rubisco の立体構造
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いままで原始生命体に近い始原菌はRubisco を有しないと考えられてきたが、我々はKOD1株内に高い炭酸固定能を有するRubisco が存在することを発見した。本酵素（Tk-Rubisco）は従来のRubisco と比較して35 倍も高い活性を有し、二酸化炭素に対する特異性も極めて高いことが判明した。Tk-Rubisco は構造的にも新規であり、前例のない五角形型10 量体構造をとっていた（右図）。また、詳細な生化学的解析の結果、本五角形構造はTk-Rubiscoの高い耐熱性に必須であることも判明した。
4）新しいchitin 代謝系の発見
Cellulose やchitin の生分解については主に細菌やカビで研究されてきたが、これらのβ-多糖は一般にその結晶性構造のために可溶性や非結晶性の基質に比べ分解されにくい。
我々はKOD1 株より、chitin 分解に関与するchitinase （ Tk-ChiA ）、deactylase 、
exo-β-D-glucosaminidase（Tk-Glm）、glucosamine-6-phosphate deaminase（Tk-Gpd）をそれぞれ同定・解析した。各酵素の基質特異性などを検討した結果、KOD1 株においてはTk-ChiAがchitin をGlcNAc2 にまで分解した後、deactylase の反応により生じるGlcN2 をTk-Glm が単糖に分解し、さらにTk-Gpd の作用によりfructose 6-phosphate にまで変換されるという経路が示唆された。これまでにこのようなchitin 分解経路は知られておらず、超好熱始原菌に特有の新規な代謝経路と考えられる。
5）構造解析に基いた超好熱菌由来タンパク質の耐熱性機構の解明
超好熱菌由来タンパク質が示す高度な耐熱性は、タンパク質科学の基礎分野のみならず、酵素を利用する様々な応用分野から注目を集めている。我々は多数のKOD1 株由来酵素の立体構造を明らかにしており、それらの耐熱性機構を解明することができた。代表的な例としてO6-methylguanine-DNA methyltransferase（Tk-MGMT）が挙げられる。Tk-MGMT とその大腸菌由来酵素（AdaC）の立体構造を比較すると、Tk-MGMT にはα-helix を安定化するhelix 内イオン結合が多数存在することが判明した。また、タンパク質全体の構造を安定化するhelix 間イオン結合も多く存在していた。大腸菌由来AdaC にはこのようなイオン結合は少なく、超好熱菌由来酵素は多数のイオン結合やイオン結合ネットワークにより高度な耐熱性を発揮していることが判った。これは上述のGDH においても同様であり、生化学的にも証明することができた。すなわち、GDH 内に存在するイオン結合ネットワークを壊すような部位特異的変異を導入した場合には、変異酵素の熱安定性が大きく低下した。
逆にイオン結合を増加させた変異酵素の耐熱性は上昇した。
6）有用酵素の利用
我々はKOD1 株のDNA polymerase（KOD DNA polymerase）の機能解析を行った結果、本酵素は従来のPCR 酵素と比較してDNA の合成速度が速く、長いDNA を合成する能力も高いことを見いだした。実際、KOD DNA polymerase を用いると、従来のTaq 酵素で２
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時間かかっていたPCR の反応時間を約25 分に短縮できた。また、KOD DNA polymerase の3'→5' exonuclease 活性を欠失させた改変型酵素と野生型酵素とを最適な割合で混合することにより、より優れた反応効率・伸長性を得ることができた。我々はさらにKOD DNA polymeraseの抗体を用いることにより、PCR 反応の初期に見られる誤増幅を抑え、極めて正確で効率の良いDNA 増幅系を確立することができた。本システムは東洋紡績社から「KOD-Plus-」システムとして上梓中であり、またLifeTechnologies 社より「PlatinumTM Pfx DNA polymerase」、Novagen 社よりHifi KOD DNA polymerase として欧米各国で販売されている。最近我々はさらにKOD DNA polymerase の結晶化・X 線構造解析を行い、その立体構造を決定した（右図）。詳細な立体構造に基いて、本酵素の伸長反応の速さ、複製能力の正確さなどがどのような構造に起因するかを解明することができた。
我々はDNA polymerase 以外にも多数の有用耐熱性酵素を同定解析している。遺伝子組換え技術の中で不可欠な酵素であるDNA ligase をはじめとし、糖質関連酵素としては、デンプンなどに見られるα1-4）結合を切断するα-amylase や環化反応を触媒してcyclodextrin を合成するcyclodextrin glucanotransferase、転移反応を触媒する4- α-glucanotransferase について生化学的諸性質を明らかにしている。
7）Thermococcus kodakaraensis KOD1 株のゲノム解析と遺伝子導入技術の開発
本研究を通じて我々は既にKOD1 株に関して100 種類以上の遺伝子を解析し、80 種類以上のタンパク質の詳細な生化学的性質を明らかにしてきた。KOD1 株は生物の進化系統樹の根に近いところに位置する極めて単純化された生命体であり、生命の基本メカニズムを理解する上で、本菌は恰好の題材であると考えられる。
また、KOD1 株は上述のように新しい特徴を有する酵素や応用可能な耐熱性酵素を多数生産している。このような背景のもと、我々はKOD1 株の全ゲノム解析を進めることにした。KOD1 株のゲノムは2,089,377 塩基対からなり、予想通り極めて短いものであった（大腸菌の40％以下）。また、遺伝子の数も少なく2000 個程度であった（右図）。KOD1 株がこのような少ない数の遺伝子で生命を維持していることから、本菌の研究KOD DNA polymerase の立体構造
KOD1 株のゲノム
KOD1 株のtrpE 遺伝子の特異的破壊実験
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を通じて生命の基本原理の解明も実現可能と期待している。
ポストゲノム研究において最も重要な研究課題は機能未知遺伝子の生理的役割を解明することである。DNA chip による網羅的遺伝子発現解析、proteome による網羅的タンパク質解析はこの目的のために有効な解析法である。我々もこれらの手法を用いて研究を進めているが、最近、もう１つ重要なシステムの構築に成功した。すなわちKOD1 株ゲノム上の任意の遺伝子を特異的に破壊する技術である。これにより機能未知遺伝子を破壊してその影響を解析することにより、その生理的役割を明らかにすることが可能となった（右図）。
KOD1 株が極めて単純な生命体であること、およびゲノム情報・DNA chip 技術・proteome技術・遺伝子破壊技術が全て確立されていることにより、数年以内に本菌の全遺伝子の機能解明も期待できる。
２．研究構想と経過の概要
深部地下極限環境（高温、高圧、無酸素、貧栄養）は古くから無菌状態であると信じられていたため、その生態系に関する研究は地表生態系と比べて大幅に遅れていた。しかし、我々は超好熱菌や石油分解菌など地下から地表に出現したとも予想される興味深い微生物を分離していたことから、深部地下には多種多様な未知微生物が存在している可能性が示唆されていた。そこで我々はこの未開拓の深部地下極限環境から新規な微生物を分離し、それらが有するであろう特殊酵素、
代謝系や環境適応戦略を解析していくことを研究目標に設定し、本プロジェクトを開始した（図１）。
研究を効率的に進めるため、我々は並行して２つのアプローチをとった。１つは様々な地下環境より土壌、水、油などのサンプルを採取し、それらから新規微生物の分離を試みた。これは主に京都大学大学院工学研究科（代表：今中忠行）で進めた。もう１つのアプローチでは我々が既に分離していた超好熱始原菌Thermococcus kodakaraensis KOD1 の遺伝子やタンパク質を中心に生化学的解析を進めた。これは主に大阪大学大学院工学研究科（代表：高木昌宏）で研究を行った。
新規微生物の分離に関しては平成12 年度までに興味深い特性を有する新規微生物を多数単離同定することができた。詳細は後述するが、超低温環境で生育できる微生物や超好熱菌では極めて珍しい好気性超好熱菌などを分離することができた。またこれらの新規微生物に関しては、有用酵素のスクリーニングも行った。低温菌からは低温でも高い活性を
図１ 本研究の概念図
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示す脂質分解酵素lipase を単離し、その酵素学的特性を明らかにした。好気性超好熱菌は好気性微生物に特有のmanganese catalase を多量に生産しており、本酵素の生化学的解析を進めた。本菌からはさらに超耐熱性を示し、優れた基質特異性を有するesterase も単離できた。いずれの酵素も既存の微生物由来酵素と異なった特性を有していることから、産業への利用が期待されている。
T. kodakaraensis KOD1 由来タンパク質の解析については、まずタンパク質の耐熱化機構の解明を目指して研究を進めた。数種のタンパク質の立体構造を明らかにし、常温菌由来酵素の構造と比較することにより、タンパク質の耐熱化に必要な構造的特徴を明らかにすることができた。主な特徴としてタンパク質内部の疎水性相互作用および分子表面のイオン結合性相互作用の増強が挙げられる。また、一般的なタンパク質が熱変性するのに対して、超好熱菌由来酵素は正しい立体構造をとるためには高温環境が必要であることも見出した。この現象を我々は「heat maturation＝熱成熟」と名付け、これは超好熱菌由来耐熱性タンパク質の新しい概念として定着している。
平成12 年度から、T. kodakaraensis KOD1 株のゲノムが極めて小さいものであることに着目して、遺伝子レベル・タンパク質レベルで網羅的な解析を開始した。遺伝子レベルではまずKOD1 株のゲノム解析を進めることにした。ゲノムが小さいことは遺伝子の数も少ないことを意味するので、KOD1 株においては生命を維持するための様々なメカニズムが極めて単純化されていることが予想された。ゲノム解析の結果、KOD1 株のゲノムは2,089,377 bp であり、約2300 のopen reading frame を有した（図２）。KOD1株は大腸菌などの細菌と比較して約半分の遺伝情報で生命を維持していることが判明した。
次の目標としてはこれらの遺伝子の機能解析を目指したが、既存の方法では機能未知遺伝子の機能を同定するための有効な解析手段が存在しなかった。そこで我々は、それまでに超好熱菌において開発されていなかった遺伝子破壊系の構築を試みた。平成13 年度の半ばに原核生物ではあまり起こらないとされていたdouble crossover 法によりKOD1株の遺伝子破壊系の構築に成功した。これは超好熱菌研究においてはmilestone（＝革命的な成果）として国際的に高く評価されている。現在多数の超好熱菌ゲノムが解読されているが、遺伝学的手法を用いて未知遺伝子の機能を解析できるのは現在のところKOD1 株のみである。
現在は遺伝子破壊系を利用した未知遺伝子の機能解析を進めており、これと並行してDNA chip を用いた各遺伝子の発現様式も検討している。さらにKOD1 株内に存在する全タンパク質の２次元電気泳動によるproteome 解析も行っている。これらの解析を通じて、多数の新規遺伝子の機能が明らかにできると期待している。これにより、単純な生命形態の１つであるT. kodakaraensis KOD1 株が如何なるメカニズム（生命の基本原理）により生
図２ T. kodakaraensis KOD1 株のゲノム
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命を維持しているかを解明できると考えている。また新規機能を有する酵素や代謝系の同
定も期待されるので、これらを利用した新しい技術の開発を行っていく予定である。
３．研究実施体制
(1) 体制
（H14.4～） （H13.4～H14.3）
超耐熱性タンパク質の構造解析を担当
（H13.4～） （～H12.3）
KOD1 株の有用酵素解析
KOD1 株のゲノム解析
超耐熱性タンパク質の構造解析を担当
KOD1 株のDNAchip 作製
KOD1 株の全遺伝子機能解析
KOD1 株のゲノム解析およびproteomics
石油分解菌HD-1 株の代謝系の解析
新規好気性超好熱菌VA1 株の解析
炭酸固定酵素の解析
新規超深度地下微生物のスクリーニング
KB700A 株由来酵素の解析
MAL1 株、KB700A 株、N1 株の解析を担当
耐熱性タンパク質グループ
関西学院大学文理学部
生命工学科
耐熱性タンパク質グループ
大阪大学大学院工学研究科
応用生物工学専攻
超好熱菌グループ
北陸先端科学技術大学院大学
材料科学研究科
超好熱菌グループ
大阪大学大学院工学研究科
応用生物工学専攻
新規微生物スクリーニンググループ
京都大学大学院工学研究科
合成・生物化学専攻
今中忠行
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４．研究中の主な活動
(1) ワークショップ・シンポジウム等
該当なし
５．研究成果の発表
(1) 論文発表
原著論文
2002 年
1. “Targeted gene disruption by homologous recombination in the hyperthermophilic archaeon
Thermococcus kodakaraensis KOD1”, T. Sato, T. Fukui, H. Atomi, and T. Imanaka, J.
Bacteriol., in press.
2. “Construction and highly cytoplasmic expression of a tumoricidal single-chain antibody
against hepatocellular carcinoma”, D. Sandee, S. Tungpradabkul, M. Tsukio, T. Imanaka, and
M. Takagi, BMC Biotechnology, in press.
3. “Biophysical effect of amino acids on the prevention of protein aggregation”, K. Shiraki, M.
Kudou, S. Fujiwara, T. Imanaka, and M. Takagi, J. Biochem., in press.
4. “Gene cloning and characterization of fructose-1,6-bisphosphate aldolase from the
hyperthermophilic archaeon Thermococcus kodakaraensis KOD1”, H. Imanaka, T. Fukui, H.
Atomi, and T. Imanaka, J. Biosci. Bioeng., 94(3), 237-243, (2002).
5. “Extremely stable and versatile carboxylesterase from a hyperthermophilic archaeon”, Y.
Hotta, S. Ezaki, H. Atomi, and T. Imanaka, Appl. Environ. Microbiol., 68, 3925-3931 (2002).
6. “Tk-PTP, protein tyrosine/serine phosphatase from hyperthermophilic archaeon Thermococcus
kodakaraensis KOD1: Enzymatic characteristics and identification of its substrate proteins”,
S.-J. Jeon, S. Fujiwara, M. Takagi, T. Tanaka, and T. Imanaka, Biochem. Biophys. Res.
Commun., 295, 508-514 (2002).
7. “The unique pentagonal structure of an archaeal Rubisco is essential for its high
thermostability”, N. Maeda, T. Kanai, H. Atomi, and T. Imanaka, J. Biol. Chem., 277, 31656-
31662 (2002).
8. “A novel candidate for the true fructose 1,6-bisphosphatase in archaea”, N. Rashid, H.
Imanaka, T. Kanai, T. Fukui, H. Atomi, T. Imanaka, J. Biol. Chem., 277, 30649-30655 (2002).
9. “A fundamental study on bio-control of environmental mosquito problems: Genetic and
biological characterization of potentially novel insecticide bacteria”, P. Luxananil, H. Atomi,
U. Chaisri, S. Tungpradabkul, S. Panyim, and T. Imanaka, J. Environ. Biotechnol., in press.
10. “Kinetic and biochemical analyses on the reaction mechanism of a bacterial ATP-citrate lyase”,
T. Kanao, T. Fukui, H. Atomi, T. Imanaka, Eur. J. Biochem., 269, 3409-3416 (2002).
11. “A membrane-bound archaeal Lon protease displays ATP-independent proteolytic activity
towards unfolded proteins along with ATP-dependent activity for folded proteins”, T. Fukui, T.
Eguchi, H. Atomi, and T. Imanaka, J. Bacteriol., 184,3689-3698 (2002).
12. “Unique presence of manganese catalase in a hyperthermophilic archaeon Pyrobaculum
calidifontis VA1”, T. Amo, H. Atomi, and T. Imanaka, J. Bacteriol., 184,3305-3312 (2002).
13. “Catalyzing “Hot” reactions: Enzymes from hyperthermophilic archaea”, T. Imanaka and H.
－385－
Atomi, The Chemical Record, 2,149-163 (2002).
14. “Pyrobaculum calidifontis sp. nov., a novel hyperthermophilic archaeon that grows under
atmospheric air”, T. Amo, M.L.F. Paje, A. Inagaki, S. Ezaki, H. Atomi, and T. Imanaka,
Archaea, 1,113-121 (2002).
15. “Tumor suppressive monoclonal antibody belonging to the VH7183 family directed to the
oncodevelopmental carbohydrate antigen on human hepatocellular carcinoma”, D. Sandee, S.
Tungpradabkul, K. Laohathai, B. Punyammalee, K. Kohda, M. Takagi, and T. Imanaka, J.
Biosci. Bioeng., 93, 266-273 (2002).
16. “Characterization of isocitrate dehydrogenase from the green sulfur bacterium Chlorobium
limicola: A carbon dioxide-fixing enzyme in the reductive tricarboxylic acid cycle”, T. Kanao,
M. Kawamura, T. Fukui, H. Atomi, and T. Imanaka, Eur. J. Biochem., 269, 1926-1931 (2002)
17. “Cellular toxicity od cadmium ions and their detoxification by heavy metal-specific plant
peptides, phytochelatins, expressed in mammalian cells”, M. Takagi, H. Satofuka, S. Amano,
H. Mizuno, Y. Eguchi, K. Hirata, K. Miyamoto, K. Fukui, and T. Imanaka, J. Biochem., 131,
233-239 (2002)
18. “Substrate recognition and fidelity of strand joining by an archaeal DNA ligase”, M. Nakatani,
S. Ezaki, H. Atomi, and T. Imanaka, Eur. J. Biochem., 269, 650-656 (2002)
19. “Characterization of an archaeal cyclodextrin glucanotransferase with a novel C-terminal
domain”, N. Rashid, J. Cornista, S. Ezaki, T. Fukui, H. Atomi, and T. Imanaka, J. Bacteriol.,
184, 777-784 (2002)
2001 年
20. “Low-temperature lipase from phychrotrophic Pseudomonas sp. strain KB700A”, N. Rashid,
Y. Shimada, S. Ezaki, H. Atomi, and T. Imanaka, Appl. Environ. Microbiol., 67, 4064-4069
(2001)
21. “Conformational stability of a hyperthermophilic protein in various conditions for
denaturation”, K. Shiraki, S. Fujiwara, T. Imanaka, and M. Takagi, Electrochemistry, 69,
949-952 (2001)
22. “Different cleavage specificities of the dual catalytic domains in chitinase from the
hyperthermophilic archaeon Thermococcus kodakaraensis KOD1”, T. Tanaka, T. Fukui, and T.
Imanaka, J. Biol. Chem., 276, 35629-35635 (2001)
23. “Isolation of bacterial strains colonizable in mosquito larval guts as novel host cells for
mosquito control”, P. Luxananil, H. Atomi, S. Panyim, and T. Imanaka, J. Biosci. Bioeng., 92,
342-345 (2001)
24. “Active subtilisin-like protease from a hyperthermophilic aechaeon in a form with a putative
prosequence”, Y. Kannan, Y. Koga, Y. Inoue, M. Haruki, M. Takagi, T. Imanaka, M.
Morikawa, and S. Kanaya, Appl. Environ. Microbiol., 67, 2445-2452 (2001)
25. “Interaction of TIP26 from a hyperthermophilic archaeon with TFB/TBP/DNA ternary
complex”, T. Matsuda, M. Fujikawa, M. Haruki, X.F. Tang, S. Ezaki, T. Imanaka, M.
Morikawa, and S. Kanaya, Extremophiles, 5, 177-182 (2001)
26. “Isolation and characterization of phycrotrophic bacteria from oil-reservoir water and oil
sands”, T. Kato, M. Haruki, T. Imanaka, M. morikawa, and S. Kanaya, Appl. Microbiol.
Biotechnol., 55, 794-800 (2001)
－386－
27. “Comparative analyses of the conformational stability between a hyperthermophilic protein
and its mesophilic counterpart”, K. Shiraki, S. Nishikori, S. Fujiwara, H. Hashimoto, Y. Kai,
M. Takagi, and T. Imanaka, Eur. J. Biochem., 268, 1-8 (2001)
28. “Extracellular synthesis, specific recognition, and intracellular degradation of
cyclomaltodextrins by the hyperthermophilic archaeon Thermococcus sp. strain B101”, Y.
Hashimoto, T. Yamamoto, S. Fujiwara, M. Takagi, and T. Imanaka, J. Bacteriol., 183,
5050-5057 (2001)
29. “Metal-binding properties of phytochelatin-related peptides”, H. Satofuka, T. Fukui, M.
Takagi, H. Atomi, and T. Imanaka, J. Inorg. Biochem., 86(2/3), 595-602, (2001)
30. “Crystal structure of a novel-type archaeal Rubisco with pentagonal symmetry”, K. Kitano, N.
Maeda, T. Fukui, H. Atomi, T. Imanaka, K. Miki, Structure, 9, 473-481 (2001)
31. “Methylguanine methyltransferase from Thermococcus kodakaraensis KOD1”, M. Takagi, Y.
Kai, and T. Imanaka, Methods Enzymol., 334, 239-248 (2001)
32. “RecA/Rad51 homolog from Thermococcus kodakaraensis KOD1”, N. Rashid, M. Morikawa,
S. Kanaya, H. Atomi, and T. Imanaka, Methods Enzymol., 334, 261-270 (2001)
33. “Chaperonin from Thermococcus kodakaraensis KOD1”, S. Fujiwara, M. Takagi, and T.
Imanaka, Methods Enzymol, 334, 293-301 (2001)
34. “Evolution of PCR Enzymes: Towards a better PCR system based on a KOD DNA
polymerase”, T. Imanaka and M. Takagi, J. Chin. Inst. Chem. Engrs., 32, 277-288 (2001)
35. “Enhanced signal transduction by a directly fused protein of interleukin-6 and its receptor”, H.
Mizuguchi, H. Mizuno, K. Yasukawa, T. Ishiguro, K. Fukui, T. Imanaka, and M. Takagi, J.
Biosci. Bioeng., 91, 299-304 (2001)
36. “Long and accurate PCR with a mixture of KOD DNA polymerase and its exonuclease
deficient mutant enzyme”, M. Nishioka, H. Mizuguchi, S. Fujiwara, S. Komatsubara, M.
Kitabayashi, H. Uemura, M. Takagi, and T. Imanaka, J. Biotechnol., 88, 141-149 (2001)
37. “Ribulose 1,5-bisphosphate carboxylase/oxygenase from Thermococcus kodakaraensis
KOD1”, H. Atomi, S. Ezaki, and T. Imanaka, Methods Enzymol., 331, 353-365 (2001)
38. “ATP-citrate lyase from the green sulfur bacterium Chlorobium limicola is a heteromeric
enzyme composed of two distinct gene products”, T. Kanao, T. Fukui, H. Atomi and T.
Imanaka, Eur. J. Biochem., 268, 1670-1678 (2001)
39. “Anthranilate synthase without an LLES motif from a hyperthermophilic archaeon is inhibited
by tryptophan”, X.-F. Tang, S. Ezaki, H. Atomi and T. Imanaka, Biochem. Biophys. Res.
Commun., 281, 858-865 (2001)
40. “Chitinase from Thermococcus kodakaraensis KOD1”, T. Imanaka, T. Fukui and S. Fujiwara,
Methods Enzymol., 330, 319-329 (2001)
41. “Thiol protease from Thermococcus kodakaraensis KOD1”, M. Morikawa and T. Imanaka,
Methods Enzymol., 330, 424-33 (2001)
42. “Crystal structure of DNA polymerase from hyperthermophilic archaeon Pyrococcus
kodakaraensis KOD1”, H. Hashimoto, M. Nishioka, S. Fujiwara, M. Takagi, T. Imanaka, T.
Inoue, Y. Kai. J. Mol. Biol., 306, 469-77 (2001)
43. “Two kinds of archaeal chaperonin with different temperature dependency from a
hyperthermophile”, M. Izumi, S. Fujiwara, M. Takagi, K. Fukui and T. Imanaka, Biochem.
Biophys. Res. Commun., 280, 581-587 (2001)
－387－
44. “Utilization of immobilized archaeal chaperonin for enzyme stabilization”, M. Izumi, S.
Fujiwara, M. Takagi, K. Fukui and T. Imanaka, J. Biosci. Bioeng., 91, 316-318 (2001)
45. “Gene cloning of an alcohol dehydrogenase from thermophilic alkane-degrading Bacillus
thermoleovorans B23”, T. Kato, A. Miyanaga, M. Haruki, T. Imanaka, M. Morikawa and S.
Kanaya, J. Biosci. Bioeng., 91, 100-102 (2001)
46. “Isolation and characterization of long-chain-alkane degrading Bacillus thermoleovorans from
deep subterranean petroleum reservoirs”, T. Kato, M. Haruki, T. Imanaka, M. Morikawa and S.
Kanaya, J. Biosci. Bioeng., 91, 64-70 (2001)
47. “Unique nucleotid structure during cell division of Thermococcus kodakaraensis KOD1”, S.-J.
Jeon, S. Fujiwara, M. Takagi, K. Fukui and T. Imanaka, J. Biosci. Bioeng., 91, 40-43 (2001)
2000 年
48. “A DNA ligase from a hyperthermophilic archaeon with unique cofactor specificity”, M.
Nakatani, S. Ezaki, H. Atomi and T. Imanaka, J Bacteriol., 182, 6424-6433 (2000)
49. “Anti-phytochelatin monoclonal antibody”, H. Satofuka, S. Amano, T. Fukui, H. Atomi, M.
Takagi and T. Imanaka, Biotechnol. Lett., 22, 1423-1428 (2000)
50. “Biochemical analysis of a thermostable tryptophan synthase from a hyperthermophilic
archaeon”, X.-F. Tang, S. Ezaki, H. Atomi and T. Imanaka, Eur. J. Biochem., 267, 6369-6377
(2000)
51. “Crystallographic study of intein homing endonuclease II encoded in the archaeal DNA
polymerase gene”, H. Hashimoto, H. Takahashi, M. Nishioka, S. Fujiwara, M. Takagi, T.
Imanaka, T. Inoue and Yasushi Kai, Acta Crystallogr. D Biol. Crystallogr., 56, 1185-1186
(2000)
52. “Alteration of product specificity of cyclodextrin glucanotransferase from Thermococcus sp.
B1001 by site directed mutagenesis”, T. Yamamoto, S. Fujiwara, Y. Tachibana, M. Takagi, K.
Fukui and T. Imanaka, J. Biosci. Bioeng. 89, 206-209 (2000)
53. “Acceptor specificity of a-glucanotransferase from Pyrococcus kodakaraensis KOD1, and
synthesis of cycloamylose”, Y. Tachbana, T. Takaha, S. Fujiwara, M. Takagi and T. Imanaka, J.
Biosci. Bioeng. 90, 406-409 (2000)
54. “Characterization of FtsZ homolog from hyperthermophilic archaeon Pyrococcus
kodakaraensis KOD1”, K. Nagahisa, T. Nakamura, S. Fujiwara, T. Imanaka, and M. Takagi, J.
Biosci. Bioeng. 89, 181-187 (2000)
55. “Effect of polyamines on histone-induced DNA compaction of hyperthermophilic archaea”, H.
Higashibata, S. Fujiwara, S. Ezaki, M. Takagi, K. Fukui, and T. Imanaka, J. Biosci. Bioeng.
89, 103-106 (2000)
56. “Screening of an oligopeptide antagonist for interleukin 6 from a random phage library”, H.
Mizuguchi, T. Kubomi, R. Nomura, K. Yasukawa, T. Imanaka and M. Takagi, Biotechnol.
Lett., 22, 1015-1020 (2000)
57. “A study on the structure-function relationship of lipopeptide biosurfactants”, M. Morikawa, Y.
Hirata and T. Imanaka, Biochim. Biophys. Acta, 1488, 211-218 (2000)
58. “Overproduction in Escherichia coli, purification and characterization of a family I.3 lipase
from Pseudomonas sp. MIS38”, K. Amada, M. Haruki, T. Imanaka, M. Morikawa and S.
Kanaya, Biochim. Biophys. Acta. 1478, 201-210 (2000)
－388－
59. “Crystallization and preliminary X-ray study of Pk--REC from a hyperthermophilic archaeon,
Pyrococcus kodakaraensis KOD1”, K. Harata, N. Ishii, N. Rashid, M. Morikawa and T.
Imanaka, Acta Crystallogr. D Biol. Crystallogr., 56, 648-649 (2000)
1999 年
60. “In vitro heat effect on functional and conformational changes of cyclodextrin
glucanotransferase from hyperthermophilic archaea.” T. Yamamoto, K. Shiraki, S. Fujiwara,
M .Takagi, K. Fukui and T Imanaka, Biochem. Biophys. Res. Commun., 265, 57-61, (1999)
61. “Identification of the gene encoding esterase, a homolog of hormone-sensitive lipase, from an
oil-degrading bacterium, strain HD-1.”, S. Mizuguchi, K. Amada, M. Haruki, T. Imanaka, M.
Morikawa and S Kanaya, J. Biochem., 126, 731-737, (1999)
62. “Pk-cdcA, encodes a CDC48/VCP homologue in the hyperthermophilic archaeon Pyrococcus
kodakaraensis KOD1: transcriptional and enzymatic characterization.”, S. J. Jeon, S. Fujiwara,
M .Takagi and T Imanaka, Mol. Gen. Genet., 262, 559-567, (1999)
63. “Hyperthermostable protein structure maintained by intra and inter-helix ion-pairs in archaeal
O6-methylguanine-DNA methyltransferase.”, H. Hashimoto, T. Inoue, M. Nishioka, S.
Fujiwara, M. Takagi, T. Imanaka and Y Kai, J. Mol. Biol., 292, 707-716, (1999)
64. “Characterization and application to hot start PCR of neutralizing monoclonal antibodies
against KOD DNA polymerase.”, H. Mizuguchi, M. Nakatsuji, S. Fujiwara, M. Takagi and T.
Imanaka, J. Biochem., 126, 762-768, (1999)
65. “Characterization of petroleum-degrading bacteria from oil-contaminated sites in Vietnam.”,
N Q. Huy, S. Jin, K. Amada, M. Haruki, N.B. Huu, D.T. Hang, D.T.C. Ha, T. Imanaka, M.
Morikawa and S. Kanaya, J. Biosci. Bioeng., 88, 100-102, (1999)
66. “Gene cloning and characterization of aldehyde dehydrogenase from a petroleum-degrading
bacterium strain HD-1.”, N. Okibe, K. Amada, S. Hirano, M. Haruki, T. Imanaka, M.
Morikawa and S. Kanaya, J. Biosci. Bioeng., 88, 7-11, (1999)
67. “Sequence and transcriptional studies of five clustered flagellin genes from hyperthermophilic
archaeon Pyrococcus kodakaraensis KOD1.”, K. Nagahisa, S. Ezaki, S. Fujiwara, T. Imanaka
and M. Takagi, FEMS Microbiol. Lett., 178, 183-190, (1999)
68. “The concept of the α -amylase family; structural similarity and common catalytic
mechanism.”, T. Kuriki and T. Imanaka, J. Biosci. Bioeng., 87, 557-565, (1999)
69. “Analysis of DNA compaction profile and intracellular contents of archaeal histones from
Pyrococcus kodakaraensis KOD1.”, H. Higashibata, S. Fujiwara, M. Takagi and T. Imanaka,
Biochem. Biophys. Res. Commun., 258, 416-424, (1999)
70. “Purification and characterization of an extremely thermostable cyclomaltodextrin
glucanotransferase from a newly isolated hyperthermophilic archaeon, Themococcus sp.”, Y.
Tachibana, A. Kuramura, N. Shirasaka, Y. Suzuki, T. Yamamoto, S. Fujiwara, M. Takagi and T.
Imanaka, Appl. Environ. Microbiol., 65, 1991-1997, (1999)
71. “Isolation of TBP-interacting protein (TIP) from a hyperthermophilic archaeon that inhibits
the binding of TBP to TATA-DNA.”, T. Matsuda, M. Morikawa, M. Haruki, H. Higashibata,
T.. Imanaka and S. Kanaya, FEBS Lett., 457, 38-42, (1999)
72. “The expression of tryptophan biosynthesis gene cluster trpCDEGFBA from Pyrococcus
kodakaraensis KOD1 is regulated at the transcriptional level as a single mRNA.”, X. Tang, S.
－389－
Ezaki, S. Fujiwara, M. Takagi, H. Atomi and T, Imanaka, Mol. Gen. Genet., 262, 815-821,
(1999)
73. “Ribulose bisphosphate carboxylase/oxygenase from the hyperthermophilic archaeon
Pyrococcus kodakaraensis KOD1 is composed solely of large subunits and forms a pentagonal
strucuture.”, N. Maeda, K. Kitano, T. Fukui, S. Ezaki, H. Atomi, K. Miki and T. Imanaka, J.
Mol. Biol., 293, 57-66, (1999)
74. “A unique chitinase with dual active sites and triple substrate binding sites from
hyperthermophilic archaeon Pyrococcus kodakaraensis KOD1.”, T. Tanaka, S. Fujiwara, S.
Nishikori, T. Fukui, M. Takagi and T. Imanaka, Appl. Environ. Microbiol., 65, 5338-5344,
(1999)
75. “Presence of a structurally novel type ribulose-1,5-bisphosphate carboxylase/oxygenase in the
hyperthermophilic archaeon, Pyrococcus kodakaraensis KOD1”, S. Ezaki, N. Maeda, T.
Kishimoto, H. Atomi and T. Imanaka, J. Biol. Chem., 274(8), 5078-5082, (1999)
76. “A unique DNase activity shares the active site with ATPase activity of RecA/Rad51
homologue (Pk-REC) from a hyperthermophilic archaeon”, N. Rashid, M. Morikawa, S.
Kanaya, H. Atomi and T. Imanaka, FEBS Letters, 445(1), 111-114, (1999)
77. “Isolation and characterization of a second subunit of molecular chaperonin from Pyrococcus
kodakaraensis KOD1: Analysis of ATPase deficient mutant”, M. Izumi, S. Fujiwara, M.
Takagi, S. Kanaya and T. Imanaka, Appl. Environ. Microbiol., 65, 1801-1805, (1999)
78. “Crystallographic studies on family B DNA polymerase from hyperthermophilic archaeon
Pyrococcus kodakaraensis strain KOD1”, H. Hashimoto, T. Matsumoto, M. Nishioka, T.
Yuasa, S. Takeuchi, T. Inoue, S. Fujiwara, M. Takagi, T. Imanaka and Y. Kai, J. Biochem
(Tokyo), 125, 983-986, (1999)
79. “Isolation and characterization of psychrotrophs from subterranean environments”, N. Rashid,
H. Kikuchi, S. Ezaki, H. Atomi and T. Imanaka, J. Biosci. Bioeng., 87 (6), 746-751, (1999)
80. “Gene Analysis and Enzymatic Properties of Thermostable β-Glycosidase from Pyrococcus
kodakaraensis KOD1”, S. Ezaki, K. Miyaoku, K. Nishi, T. Tanaka, S. Fujiwara, M. Takagi, H.
Atomi and T. Imanaka, J. Biosci. Bioeng., 88,130-135, (1999)
1998 年
81. “Ion pairs involved for maintaining a thermostable structure of glutamate dehydrogenase
(GDH) from a hyperthemophilic archaeon”, R.N.Z.A. Rahman, S. Fujiwara, H. Nakamura, M.
Takagi and T. Imanaka, Biochem. Biophys. Res. Comm., 248, 920-926, (1998)
82. “Sequence analysis of glutamate dehydrogenase (GDH) from the hyperthermophilic archaeon
Pyrococcus sp. KOD1 and comparison of enzyme characteristics of native and recombinant
GDHs”, R.N.Z.A. Rahman, S. Fujiwara, M. Takagi and T. Imanaka, Mol. Gen. Genet., 257,
338-347 (1998)
83. “Comparison of two glutamate producing enzymes from the hyperthermophilic archaeon
Pyrococcus sp. KOD1” B. Jongsareejit, S. Fujiwara, M. Takagi and T Imanaka, FEMS
Microbiol. Lett., 158, 243-248 (1998)
84. “The O6-methylguanine-DNA methyltransferase from a hyperthermophilic archaeon
Pyrococcus sp. KOD1: a thermostable repair enzyme”, M. M. Leclere, M. Nishioka, T. Yuasa,
T. Fujiwara, S. Takagi and T. Imanaka, Mol. Gen. Genet., 258, 69-77 (1998)
－390－
85. “Rational design for stabilization and optimum pH shift of serine protease AprN”, A. Masui,
N. Fujiwara, K. Yamamoto, M. Takagi and T. Imanaka, J. Ferment. Bioeng., 85, 30-36 (1998)
86. “Characterization of two intein homing endonucleases encoded in the DNA polymerase gene
from Pyrococcus kodakaraensis strain KOD1”, M. Nishioka, S. Fujiwara, M. Takagi and T.
Imanaka, Nucleic Acids Res., 26, 4409-4412 (1998)
87. “Phylogenetic analysis and effect of heat on conformational change of ferredoxin from
hyperthermophilic archaeon Pyrococcus sp. KOD1”, M.A. Siddiqui, S. Fujiwara, M. Takagi
and T. Imanaka, J. Ferment. Bioeng., 85, 271-277 (1998)
88. “Crystal structure of aspartyl-tRNA synthetase from Pyrococcus kodakaraensis KOD;
archaeon specificity and catalytic mechanism of adenylate formation”, E. Schmitt, L.
Moulinier, S. Fujiwara, T. Imanaka, J. Thierry and D. Moras, EMBO J., 17, 5227-5237 (1998)
89. “Archaeon Pyrococcus kodakaraensis KOD1: application and evolution”, S. Fujiwara, M.
Takagi and T. Imanaka, Biotechnol Annu. Rev., 4, 259-284 (1998)
90. “Gene cloning and characterization of recombinant RNase HII from a hyperthermophilic
archaeon”, M. Haruki, K. Hayashi, T. Kochi, A. Muroya, Y. Koga, M. Morikawa, T. Imanaka
and S. Kanaya, J. Bacteriol., 180, 6207-6214 (1998)
91. “In vitro heat effect on heterooligomeric subunit assembly of thermostable indolepyruvate
ferredoxin oxidoreductase”, M.A. Siddiqui, S. Fujiwara, M. Takagi and T. Imanaka, FEBS
Lett., 434, 372-376 (1998)
92. “Thermostable glycerol kinase from a hyperthermophilic archaeon: gene cloning and
characterization of the recombinant enzyme”, Y. Koga, M. Morikawa, M. Haruki, H.
Nakamura, T. Imanaka and S. Kanaya, Protein Engineering, 11, 1219-1227, (1998)
93. “Crystallization and preliminary X-ray crystallographic analysis of archaeal O6
-methylguanine-DNA methyltransfease”, H. Hashimoto, M. Nishioka, T. Inoue, S. Fujiwara,
M. Takagi, T. Imanaka and Y. Kai, Acta Crystallographica, D54, 1395-1396, (1998)
94. “Production of alkane and alkene from CO2 by a petroleum-degrading bacterium”, M.
Morikawa, T. Iwasa, S. Yanagida and T. Imanaka, J. Ferment. Bioeng., 85, 243-245, (1998)
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106. 「PCR 法」：高木昌宏。微生物利用の大展開、エヌ・ティー・エス、Pg.495-500、2002.
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113. 「地球環境とバイオテクノロジー特集」：今中忠行。BIOINDUSTRY、19 巻、１号、
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114. 「極限環境微生物の特殊能力の利用」：跡見晴幸。BIOINDUSTRY、19 巻、１号、18-27、
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115. 「生分解性プラスチックの微生物生産」：福居俊昭。BIOINDUSTRY、19 巻、１号、
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116. “Apoptotic signal transduction by cadmium ion and detoxification by plant peptides”,
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117. 「超好熱菌由来タンパク質の準安定構造とネイティブ構造への転移ー熱成熟とよば
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118. 「構造的に新しい超好熱始原菌由来Rubisco」：跡見晴幸。酵素工学ニュース、第47
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120. 「環境工学と酵素利用技術」：今中忠行。最新酵素利用技術と応用展開、監修：相澤
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122. 「誘導・制御」：今中忠行。生物工学実験書、日本生物工学会編、培風館、80-81、2001.
123. 「石油発酵」：今中忠行。発酵ハンドブック、共立出版、241、2001.
－392－
124. 「極限環境微生物の探索と利用」：今中忠行。バイオサイエンス＆インダストリー、
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125. 「微生物のCalvin-Benson 回路と3-Hydroxypropionate 回路」：跡見晴幸、今中忠行。日
本生物工学会誌、79 巻、10 号、395-400、2001.
126. 「21 世紀のバイオテクノロジー」：今中忠行。高分子科学とバイオテクノロジーとの
キャッチボール、ポリマーフロンティア21 シリーズ、高分子学会編、エヌ・ティー・
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127. 「地下微生物の多様性と炭素循環への寄与」：今中忠行、跡見晴幸。月刊地球「プレ
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128. 「環境バイオテクノロジーの現状と将来展望」：今中忠行。植物による環境負荷低減
技術-ファイトレメディエーション、エヌ・ティー・エス、1-46、2000.
129. 「21 世紀へ向けて-多様な微生物資源と遺伝子資源を求めて」：今中忠行。生物工学会
誌特別号「発酵工学20 世紀のあゆみ」－バイオテクノロジーの源流を辿る－ 日本
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130. 「地下微生物の探索と利用」：今中忠行。人類とバイオ－ゲノム解析と遺伝子特許－
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131. 「微生物の多様性と応用」：今中忠行。ケミカルエンンジニヤリング、Vol.45, No.11,
12-17, 2000
132. 「微生物による炭酸固定」。跡見晴幸。ケミカルエンンジニヤリング、Vol.45, No.11,
24-30, 2000
133. 「極限環境の微生物」。今中忠行。生物の科学 遺伝 「地球の進化・生命の進化」
別冊No.12、93-102、2000.
134. 「資源に関連した地下微生物活動と物理探査への期待」：今中忠行。物理探査、第53
巻、第６号、489-498、2000.
135. 「生物を利用した環境保全」：今中忠行。バイオサイエンスとインダストリー、Vol.57,
No.4, 234, 1999.
136. 「バイオ・レメディエーション：自然の浄化作用が究極の手法」：今中忠行。化学、
Vol.54, No.1, 31-33, 1999.
137. 「耐熱性タンパク質と超好熱菌の利用」：藤原伸介、高木昌宏、今中忠行。
BIOINDUSTRY、Vol.16, No.12, 13-20, 1999.
138. 「超好熱始原菌シャペロニンの機能と応用」：今中忠行。酵素工学ニュース、４月号,
21-24, 1999.
139. 「最も高い温度に耐える微生物」：今中忠行。別冊化学：化学の世界記録集、132-135,
1999.
140. 「DNA シークエンシングの化学反応」：今中忠行、跡見晴幸。化学と教育、Vol.47, No.4,
260-263, 1999.
141. 「地下極限環境微生物の探索と利用」：今中忠行、跡見晴幸。月刊海洋・号外No.19,
161-167, 1999.
142. 「地球の未来を任されるか？石油をつくる細菌」：今中忠行。ミクロスコピア、Vol.16,
No.3, 176-181, 1999.
143. 「超好熱菌Rubisco による炭酸固定？」：跡見晴幸、今中忠行。バイオサイエンスとイ
ンダストリー、Vol.57, No.10, 689-690, 1999.
144. 「CO2 問題に対する一私見」：今中忠行。RITE NOW、Vol.33, 2-3, 1999.
－393－
145. 「環境バイオテクノロジーの現状と将来」：今中忠行。環境管理、Vol.35, No.6, 513-515,
1999.
146. Production of alkane and alkene from CO2 by a petroleum-degrading bacterium strain HD-1.
Masaaki Morikawa, Toru Iwasa, K. Nagahisa, S. Yanagida, & Tadayuki Imanaka, Studies in
Surface Science and Catalysis, Vol.114, 467-470, 1998.
147. 「超好熱菌研究の最前線」：今中忠行。日本生物工学会誌、Vol.76, No.6, 255-256, 1998.
148. 「超好熱始原菌における酵素の分子認識の多様性」：江崎 聡、跡見晴幸。日本生物
工学会誌、Vol.76, No.6, 269-271, 1998.
149. 「炭酸ガスからの石油生成」：森川正章、金 沙、金谷茂則、今中忠行。日本農芸化
学会誌、Vol.72, No.4, 532-534, 1998.
150. 「Flagellin を用いた細胞表層提示システム」：江崎 聡、今中忠行。日本生物工学会誌、
Vol.76, No.12, 495-497, 1998.
151. 「CO2 から石油を作る細菌」：今中忠行。Microbes and Environments, Vol.13, No.3,
171-175, 1998.
152. 「タンパク質工学」：今中忠行。21 世紀の天然・生体高分子材料、289-297, 1998.
153. 「Chemical Biology の勧め」：今中忠行。化学と工業、Vol.51, No.6, 886-888, 1998.
154. 「100℃でも生きる菌」：今中忠行。ゑれきてる、No.70, 5, 1998.
(2) 特許出願
１．発明名称：「遺伝子のターゲティング破壊法」
事業団整理番号：A062P96
出願日 ：平成14 年８月30 日
（超好熱始原菌Thermococcus kodakaraensis KOD1 株のゲノム上の全ての遺伝子を網
羅する特許）
(3) 新聞報道等
①新聞報道
新聞社名 タイトル 年月日
NTS ニュース 生命の基本原理解明、人工細胞完成も射程距離に入って
います。微生物利用はまさに大展開。
Jul. 2002
産経新聞 石油生成する微生物解明へ Apr.22, 2002
朝日新聞 人工石油へ道 合成菌解析 遺伝子、2194 まで探索 Mar.7, 2002
静岡新聞 調査進む相良油田 Feb.4, 2002
産経新聞 石油合成能力に期待
超高熱始原菌「KID 1」試薬の高性能化に威力
Jan. 1, 2002
中日新聞 相良油田を２月から掘削 Dec.20, 2001
静岡新聞 相良油田 微生物関与実証へ Dec.20, 2001
中日新聞 「微生物が石油生成」検証 Dec.20, 2001
京都新聞 石油の出来方、定説覆す？ Dec.18, 2001
北海道新聞 油田形成に細菌関与？ Jul.24, 2001
岩手日報 油田つくったのは細菌？ 意外な仮説発掘調査へ Jul.24, 2001
－394－
新聞社名 タイトル 年月日
秋田魁新報 細菌が油田をつくる？ 石油の成因論に新説 Jul.24, 2001
山形新聞 石油つくったのは細菌 Jul.24, 2001
ﾃﾞｰﾘｰ東北 細菌が油田をつくった？来年２月にも掘削調査 Jul.24, 2001
北日本新聞 静岡県で発見の石油生成細菌 油田形成に関与か Jul.24, 2001
信濃毎日新聞 「化石燃料の石油」に意外な成因説
細菌が働き油田作る？
Jul.24, 2001
中日新聞 細菌が油田をつくる？石油成分を蓄積仮説検証へ Jul.24, 2001
岐阜新聞 「油田」つくったのは細菌？仮説検証へ掘削調査 Jul.24, 2001
京都新聞 油田作ったのは細菌の働き？発掘調査で検証へ
なぞに迫る試み 人工油田の夢も
Jul.24, 2001
神戸新聞 石油生成菌のナゾ解明 Jul.24, 2001
大分合同新聞 細菌が石油作った？静岡で掘削調査へ
起源のなぞに迫る試み
Jul.24, 2001
宮崎日日新聞 細菌が油田をつくる？ 相良油田を掘削調査へ Jul.24, 2001
琉球新報 石油つくったのは細菌？
起源のなぞに迫る 細菌使う人工油田の夢も
Jul.24, 2001
日本海新聞 油田つくったのは細菌？ 意外な仮説が浮上 Jul.25, 2001
高知新聞 油田作ったのは細菌？ 京大教授らが仮説 Jul.25, 2001
日刊工業新聞 21 世紀の科学技術 －京大工学研究科の挑戦－
今中教授 超好熱細菌を応用
Jul.17, 2001
読売新聞 CO2 から石油を作る細菌 温暖化資源枯渇一挙に解決!?
課題は合成効率と水素
Jul. 4,2001
信濃毎日新聞 極限環境微生物 日光や酸素なしで生きる
生命の歴史探る糸口に
Jul. 4,2001
静岡新聞 別の条件下で石油生成 相良油田の「石油分解菌」人工
的生産の可能性 京大今中教授ら証明
Jan.16,2001
日本経済新聞 自然界に隠された遺伝子情報が石油にとって代わる
新資源争奪戦が始まった 微生物が富を生む
Jan. 3,2001
読売新聞 微生物を生活に応用 地下に眠る未知の可能性
エネルギー源、環境汚染防止 研究開発急ピッチ
Jan.20,2000
日本経済新聞 「地球への処方せん」 環境などに挑む May 30,2000
日本経済新聞 微生物活用で研究 環境浄化ビジネス
京都府ｸﾞﾘｰﾝﾍﾞﾝﾁｬｰ研 京大などと検討
Sep.15 1999
日刊工業新聞 がぜん脚光浴びる始原菌 農業廃棄物の処理
植物改良に役立つ
Apr.6,1999
日刊工業新聞 光合成鍵酵素を持つ超好熱始原菌 CO2 の削減に貢献 Apr.6,1999
②受賞
平成10 年度日本生物工学会論文賞受賞
平成11 年度日本生物工学会論文賞受賞
平成13 年度日本生物工学会生物工学賞受賞
平成13 年度有馬啓記念バイオインダストリー協会賞受賞
－395－
(4) その他
我々が開発した耐熱性DNA polymerase（KOD DNA polymerase）が国内では東洋紡績社、
海外ではInvitrogen 社やNovagen 社により販売開始となった。また、当研究室が開発した
糖質関連酵素が江崎グリコの糖質加工プロセスに実用化された。
=========================================================
耐塩性藻類を用いた人口石油生産プロセスの開発
堀内淳一
http://www.saltscience.or.jp/general_research/2005/200507.pdf
=========================================================
オイル産生微細藻～二酸化炭素を吸収してオイルを作る画期的な藻で次世代バイオ燃料を
https://www.blwisdom.com/technology/series/ecotech/item/1841-02.html
テクノロジー WISDOM編集部 2010年12月13日
ライトの点灯時間や温度などを変えて培養される微細藻。この中から人類のエネルギー危機を救う藻が発見されるかもしれない。
ライトの点灯時間や温度などを変えて培養される微細藻。この中から人類のエネルギー危機を救う藻が発見されるかもしれない。
将来的な枯渇と二酸化炭素の排出が問題となっている石油に代わるエネルギーは、人類にとって喫緊のテーマだ。現在、代替燃料をめぐって世界でさまざまな研究が行われているが、中でも注目を集めているのが「オイルを作り出す藻」である。日本で、この分野の研究をリードする伊藤卓朗氏に聞いた。
高等植物の10倍以上の二酸化炭素吸収能力
慶應義塾大学
先端生命科学研究所
研究員 生命科学博士
伊藤 卓朗さん
先端生命科学研究所
研究員 生命科学博士
伊藤 卓朗さん
藻が人類を救うかもしれない。その名は「オイル産生微細藻」。一定の条件の下、この藻類は二酸化炭素を吸収して、オイルを細胞内に産生し、蓄える。このオイルは代替燃料として利用できるため、温暖化ガス削減とエネルギー問題に役立つ一石二鳥の効果がある。
オイル産生微細藻は、複雑多岐な藻類の中で植物油や石油に相当する炭化水素を作り出す藻類を指す。
コンブやワカメなどの多細胞藻類に対して、微細藻は100マイクロメートル以下の小さな単細胞藻類である。これらは海や淡水、地表や雪上などいたるところに繁殖し、その種類は膨大で未知の種も多い。
日本におけるオイル産生微細藻の研究で、現在、最先端を走っている慶應義塾大学先端生命科学研究所の伊藤卓朗研究員（32歳、生命科学博士）はこう語る。
「藻類は10前後の系統群に分類できますが、このうちのわずか1系統群が陸上植物に進化しました。それほど藻類は多様性に富んでいるのです。その中で、高度に脂質を蓄積する微細藻は、すでに複数の分類群から見つかっています」
バイオ燃料を作るにはトウモロコシや大豆、あるいはアブラヤシから作られるパームオイルなども利用されているが、食料を燃料に転用することで食料不足を招く危険やアブラヤシ栽培のために森林が失われる恐れもある。
この点、微細藻であれば食料と競合せず、工業的に培養できるので単位面積当たりの生産性が高等植物の数倍になる。また、森林伐採などする必要もなく、高等植物の栽培に適さないやせた荒れ地などを利用できる。
さらに、メリットは微細藻類が高等植物の10倍以上の二酸化炭素を吸収する能力があることだ。企業が生産活動で排出する二酸化炭素を吸収させながら、同時にバイオ燃料を生産することも可能になる。
そもそも、油田は太古の微細藻類の大量の死骸が海底に堆積し、数億年かけて石油に変質し形成されたものである。その意味では、人類が石油の生みの親である藻類にエネルギー源を求めるのも必然かもしれない。
伊藤氏たちの研究チームでは現在、国内のさまざまな自然環境からオイル産生微細藻を収集、培養して、分析を進めている。すでに400株以上を調査し、そのうち数十株がオイルを蓄積することを特定した。しかし、なぜ、どのようなメカニズムでオイルを産生するのか、微細藻がオイルを作るのは生育する環境によるものか、属や種に関係するのか、まだわかっていない。
そのため、伊藤氏らは未開の地とも言えるオイル産生藻類の系統的調査と共に、後述する「メタボローム解析」という慶應義塾大学先端生命科学研究所で開発された新技術を駆使して、オイル産生藻の代謝（細胞内で、ある物質を他の物質に変換する化学反応）を研究している。
単細胞藻類といえども代謝の仕組みは実に複雑で、数万におよぶ代謝物質が存在すると言われている。しかし、藻類の代謝を研究する専門家は少なく、未知の物質も多い。
基礎研究と同時に実用化に向けた開発も進んでおり、オイル産生藻の中でも、増殖速度が速く、軽油に変換できる植物油を作る「シュードコリシスチス エリプソイディア（仮名※）」（Pseudochoricystis ellipsoidea：以下、P.e）をバイオ燃料生産に利用する研究を株式会社デンソーと共同で行っている。
デンソーは今年7月にP.eを育てる培養槽を公開した。今後、工場から排出される二酸化炭素をP.eに吸収させ、年間320リットルの軽油を生産し、その燃料で工場のボイラーを稼動させる。つまり、二酸化炭素をリサイクルして生産活動を持続する試みだ。
※学術的に正式記載されていないため、仮名となっている。
原油価格高騰で微細藻に再び脚光
「私たちが扱う藻類は摂氏10～30度と、生育可能な温度の幅が広いため、実験室での培養は難しくありません。しかし、屋外で効率よく培養するには、自然の池や沼を使うことは難しい。野外に大規模なプールを作ることになるでしょう。植物工場で培養する手もありますが、問題はコストです。現在、藻から作る燃料はガソリンの数倍から十倍近い価格になると見積もられています。コストを下げるためには、オイルの生産効率を高めることが必要です。そのために代謝のメカニズムの解析や、より最適な株（藻類）の探索を行っているのです」P.eは岩手県釜石市にあった株式会社海洋バイオテクノロジー研究所（現在は北里大学海洋バイオテクノロジー釜石研究所）に在籍していた藏野憲秀博士らが温泉地から発見した藻だ。同研究所は海洋微生物約５万株を収集、解析し、世界有数の海洋微生物ライブラリーを作り上げた。
伊藤氏は2006年に同僚の研究者が学会で「油を作る妙な藻の発表を聞いた」ことを知る。それがP.eだった。ピンと来た伊藤氏は釜石の研究所に話を聞きに行った。
「メタボローム解析を使って、藻を生理学的に研究したら面白いのではないかと思ったのです」
伊藤氏は海洋バイオテクノロジー研究所と共同研究をスタートした。しかし、いざ研究を始めてみると、過去のオイル産生微細藻の研究データは意外に少なかった。
実は、藻にオイルを作らせる研究は以前からあった。アメリカでは1970年代後半から燃料を作る藻の探索が始まり、実証実験まで行っている。しかし、コスト的に原油に太刀打ちできず、やがて研究は廃れた。
日本でも国家プロジェクトが立ち上がり、研究が進み始めたが、同じ理由でやはり立ち消えになった。しかも、この間の研究データは論文として発表されているものが少ないのだ。伊藤氏たちは一つ一つ手探りで研究を進めた。
オイル産生藻が息を吹き返したのは、2007年である。イラク戦争を機に原油価格の上昇が始まり、2008年にかけて暴騰が続く中、アメリカのブッシュ大統領（当時）が一般教書演説で「今後10年間でガソリン消費を20％削減する」「2017年までに年間350億ガロンの再生可能燃料や代替燃料の使用を義務づける」などのエネルギー政策を発表した。また、アル・ゴア元副大統領が環境保護の啓発活動でノーベル平和賞を受け、温暖化ガス排出削減の動きが世界的に高まった。
こうした中で、アメリカでは藻から燃料を作る気運が一気に広がり、ベンチャー企業が次々と生まれた。
「100社を超えるベンチャーがオイル産生藻に取り組んでおり、日本に比べると巨額の資金が動いています。すでに藻から作った燃料で飛行機を飛ばす実験も行っています」
誰もやりたがらない研究をやりたい
アメリカの資金力は侮れないが、代謝の基本的メカニズムから地道に研究を積み重ねている伊藤氏たちのチームも世界の先端を行く。「根幹的な仕組みを解き明かすには時間がかかるかもしれないが、それがわかればもっと早く大量にオイルを作る方法も確立できると考えています」
伊藤氏は代謝物質の研究をこうたとえる。
「複雑に絡み合う電車の路線図で言うと、いま私たちがやっていることは各駅にいる乗客数（物質量）を調べて数えているようなものです。そこからさらに路線図や電車のダイヤ（メカニズム）がわかれば役に立つものになる」
どの物質がなんのためにどのような物質に変換されるのか、複雑な代謝の仕組みが路線図のようなマップに整理されたとき、研究は大きく飛躍するはずだ。
伊藤氏は、現在勤める慶應義塾大学先端生命科学研究所のある鶴岡市出身だ。鶴岡工業高等専門学校時代から生物の不思議さに興味を持ち、卒業研究でも藻の細胞死をテーマにしたというのだから、藻に縁があるのかもしれない。
もともとは海の生物を研究したいと思っていたが、進学した大学で植物の研究を行うようになり、花の形と性分化に関する研究で博士号を取得した。2001年に故郷の鶴岡に先端生命科学研究所が開設され、伊藤氏は東北大学大学院を修了後、2006年に同研究所に就職した。
「面白いテーマではあるけれども、取っつきにくくて誰もやりたがらないような研究に挑戦したいと思っていました」という伊藤氏にとって、微細藻の代謝の研究は格好のテーマであった。
「将来的には藻から作るオイルを石油に取って代わるものにしたい。燃料だけでなく、プラスチックも衣料品の原料も代替可能にしなければなりません。早く細胞内の仕組みを明らかにして、燃料以外のマテリアルを作ることができるようにしたい」
海外のメディアや専門家からも問い合わせが来るほど、伊藤氏のチームの研究は世界的に注目を集めている。
「社会に役立ちながら、新しい発見ができれば研究者冥利に尽きますね」
今後、人類にとって福音となる物質が藻から発見される可能性もある。伊藤氏の研究に注目していきたい。
メタボローム分析装置に入れる試料を最終確認する伊藤氏。この装置の発明によって、藻の細胞内の代謝物質の分析が一気に進んだ。
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[ScienceNews] （２５）「藻」からバイオ燃料 加速する研究開発
公開日: 2011/10/25
2011年 5分
新たなバイオ燃料の原料として最も期待されているのが「藻」の仲間です。その研究開発
JSTサイエンスニュース：http://sc-smn.jst.go.jp/sciencenews/
新たなバイオ燃料の原料として最も期待されているのが「藻」の仲間です。その研究開発
JSTサイエンスニュース：http://sc-smn.jst.go.jp/sciencenews/
テクノ・ギャラリー （４）驚き！「藻」がCO2から石油をつくる
公開日: 2014/01/24
1999年 29分
出光興産（株）中央研究所のテーマリーダー、村上信雄に焦点を当てる。今日の化石燃料
人物
科学館／研究所
村上 信雄 出光興産株式会社 中央研究所 遠藤守哉（ナレーター） 青二プロダクション 出光興産株式会社 中央研究所
出光興産（株）中央研究所のテーマリーダー、村上信雄に焦点を当てる。今日の化石燃料
人物
科学館／研究所
村上 信雄 出光興産株式会社 中央研究所 遠藤守哉（ナレーター） 青二プロダクション 出光興産株式会社 中央研究所
Making Algae Fuels- Algae: 'The ultimate in renewable energy' -OIL
アップロード日: 2011/06/25
http://webmediagloballdb.blogspot.com/
Making Algae Fuels- Algae: 'The ultimate in renewable energy' -OIL
http://www.nutraingredients-usa.com/O...
"Aurora Algae is now the first global company to begin a commercial project for bioproduct and biofuel production based on photosynthetic marine microalgae," said Greg Bafalis, CEO of Aurora Algae.
California's Aurora Algae has signed off on the engineering contract for its commercial facility in Western Australia, as the company edges towards the production of thousands of tonnes of algae-based biomass annually.
http://www.oilgae.com/
Making Algae Fuels Commercially Viable
Algae biofuels are certainly the best alternative for fossil fuels. However, the very high production costs of algae fuels questions the economic viability of the fuel and creates uncertainties about sustainable production. What are all the possible ways to cut the production costs so as to make algae fuels a reality?
http://www.exxonmobilperspectives.com...
The next phase of algae biofuels
One year has passed, and I'm excited to say we're entering the next phase of our program. Today, we announced the opening of a new state-of-the-art greenhouse facility at the SGI headquarters in La Jolla, Calif. The greenhouse will be home to the next level of research and testing in our algae biofuels program. SGI and ExxonMobil researchers are already using the facility to test whether large-scale quantities of affordable fuel can be produced from algae.
Making Algae Fuels- Algae: 'The ultimate in renewable energy' -OIL
http://www.nutraingredients-usa.com/O...
"Aurora Algae is now the first global company to begin a commercial project for bioproduct and biofuel production based on photosynthetic marine microalgae," said Greg Bafalis, CEO of Aurora Algae.
California's Aurora Algae has signed off on the engineering contract for its commercial facility in Western Australia, as the company edges towards the production of thousands of tonnes of algae-based biomass annually.
http://www.oilgae.com/
Making Algae Fuels Commercially Viable
Algae biofuels are certainly the best alternative for fossil fuels. However, the very high production costs of algae fuels questions the economic viability of the fuel and creates uncertainties about sustainable production. What are all the possible ways to cut the production costs so as to make algae fuels a reality?
http://www.exxonmobilperspectives.com...
The next phase of algae biofuels
One year has passed, and I'm excited to say we're entering the next phase of our program. Today, we announced the opening of a new state-of-the-art greenhouse facility at the SGI headquarters in La Jolla, Calif. The greenhouse will be home to the next level of research and testing in our algae biofuels program. SGI and ExxonMobil researchers are already using the facility to test whether large-scale quantities of affordable fuel can be produced from algae.
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Algae: The Future of Biodiesel
公開日: 2012/12/04
Project about Algal Biodiesel for IDSM 140 at Truman State University
By: Tyler Smith, Bing Zheng, Nathan Wikle and Mayra Garcia Hernandez
no copyright intened
By: Tyler Smith, Bing Zheng, Nathan Wikle and Mayra Garcia Hernandez
no copyright intened
Algae to Bio-Crude in Less Than 60 Minutes
公開日: 2013/12/17
Engineers have created a chemical process that produces useful crude oil just minutes after engineers pour in harvested algae -- a verdant green paste with the consistency of pea soup. The PNNL team combined several chemical steps into one continuous process that starts with an algae slurry that contains as much as 80 to 90 percent water. Most current processes require the algae to be dried -- an expensive process that takes a lot of energy. The research has been licensed by Genifuel Corp. Read the full story here: http://www.pnnl.gov/news/release.aspx...
For more on PNNL's bio-based product research, visit http://www.pnl.gov/biobased/.
For more on PNNL's bio-based product research, visit http://www.pnl.gov/biobased/.
Transforming Modern Agriculture
公開日: 2012/12/04
The unique characteristics of algae offer a compelling solution to many of our modern global challenges.
At Aurora Algae, we're refining the science and technology of growing algae crops on arid, non-productive land, using little more than sunlight, seawater, and carbon dioxide.
www.aurorainc.com
At Aurora Algae, we're refining the science and technology of growing algae crops on arid, non-productive land, using little more than sunlight, seawater, and carbon dioxide.
www.aurorainc.com
「二酸化炭素排出抑制に資する革新的技術の創出」
オイル産生緑藻類Botryococcus（ボトリオコッカス）
高アルカリ株の高度利用技術
筑波大学大学院生命環境科学研究科・教授
渡邉 信
http://www.jst.go.jp/kisoken/crest/report/heisei20/pdf/pdf04/04-006.pdf
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微細藻類を用いたバイオ燃料生産の将来展望
電源株式会社 松本光史
http://www.oceanquest.jp/(S(nvfewq45ch4siiaj3bhfnh55))/contents/paper/12.pdf
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欧州における次世代型バイオ燃料への取組み （その１）
http://www.jsim.or.jp/kaigai/1107/003.pdf
欧州における次世代型バイオ燃料への取組み （その２）
http://www.jsim.or.jp/kaigai/1108/003.pdf
欧州における次世代型バイオ燃料への取組み （その３）
http://www.jsim.or.jp/kaigai/1109/004.pdf
欧州における次世代型バイオ燃料への取組み （その４）
http://www.jsim.or.jp/kaigai/1107/004.pdf
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http://www.asahi-net.or.jp/~vb7y-td/k4/141119.htm
北里大学の田口さんが作るＨＰ（環境と微生物）から今回は、考察 http://tag.ahs.kitasato-u.ac.jp/tag-wada/noframe/index-je.htm したいと思います。
Ｆより このＨＰを見ると、今後の細菌や微生物への期待が大きくなる。 石油は太古のＣＯ２と太陽エネルギーを光合成したものであり、 そのため、石油を燃やすとＣＯ２とエネルギーが出てくることにな る。しかし、人間はその液状の石油の便利さから大量消費をしてし まい、太古の高温な環境と同じ環境に現代の地球をしようとしてい る。 しかし、太古にはないものがある。植物、微生物の進化発達があり 、その進化した細菌を見つけて、利用促進すればいいのです。 この細菌・微生物の研究を北里大の田口さんは公開していただいて いるため、私のような門外漢にも知ることができるのです。インタ ーネットの素晴らしさですね。このようにバイオ研究からもジャパ ン・エポックの準備は整っているのです。あとはどう量産化や工業 化するかなのでしょうね。それと有能な研究者を増員して、細菌を 探すこと、量産化の方法を見つけること、特に酸素が無い状態での み増殖する嫌気性菌の簡単な培養ができる装置の開発が必要なので しょうね。 プラスチックを作る微生物や二酸化炭素を固定する微生物について も研究しているようで、今後、このような菌も報告していただける ようですので、期待したいですね。
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
５．水素を作る細菌 http://tag.ahs.kitasato-u.ac.jp/tag-wada/noframe/e005.htm
水素を作る微生物は、1940年代より色々見付けられ、藻類と細菌に 分類される。糸状性ラン藻や緑藻(例えばクロレラ)は、非常に面白 い生き物で、二酸化炭素と光を利用して水を分解して水素を作れま す。しかし、反応速度が非常に遅い短所がある。水素を作る細菌は 、光合成細菌と通常の細菌に分けられ、後者は更に大腸菌のような 酸素があっても無くても増殖する通性嫌気性菌と酸素が無い状態で のみ増殖する嫌気性菌(例えばガス壊疽菌)に分けられます。 光合成性細菌は、酢酸のような有機物と光を用いて水素を発生さ せます。光合成性細菌の水素生成反応は、効率が高く生成速度も藻 類より大きい。条件をそろえれば、太陽電池と近い能力を有してい ます。 嫌気性水素生成菌は、主にクロストリジウム属の細菌に多い。 この種類の細菌は、糖等を有機酸と水素に変換します。私共研究室 でシロアリより分離したクロストリジウム属の細菌は、非常に優秀 で１グラムの砂糖から半日で牛乳ビン１本程度の水素を作ります。 この水素生成速度は、光合成菌のおおよそ千倍であります。 将来は、嫌気性水素生成菌で植物を水素と有機酸に分解し、有機 酸を光合成菌で水素に変換する研究が進むと、廃棄物の処理とエネ ルギー問題が解決できる可能性があります。
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
その４．麦ワラを水素に変換する．
http://tag.ahs.kitasato-u.ac.jp/tag-wada/noframe/e016.htm
私達がシロアリから分離した菌株には、セルロースやヘミセルロー スを水素に変換する株もあります。その１株がClostridium sp. X53 という名前の菌株で、キシロースの多糖体である大麦由来のキシラ ンを直接水素に変換できる世界で最初の珍しい菌です。 pH6.0で 40℃に保温すると、培養開始２時間後よりキシラナーゼ活 性が検出されるようになり、培養開始後８時間で最高値に達する。 水素の産生も全く同じ条件で進行し、上に記載したSP２株とほぼ同 じ速さで水素を発生できます。しかし、キシランからの水素総生成 量は、残念ながらキシロースからの水素量の80%程度で止まってしま います。原因はよく判りませんが、市販品のキシランは糖以外の不 純物を多く含んでいるならば、水素生成効率はそれほど悪くないも のと考えられます。 ヘミセルロースは、農産物の残さに多くふくまれる成分ですから 、地球上には莫大な量が毎年作られると同時に廃棄されていること になります。このような状況を考慮すると、ヘミセルロースを加水 分解できる菌並びにその加水分解物を水素や有機溶媒などに変換で きる菌は、今後とも重要且つ貴重な宝物となりましょう。 私達もClostridium sp. X53よりももっと優れた菌株の入手に力 を入れてがんばっています。水素生成菌とメタン菌とは、かなり性 質が異なります。水素生成菌は、メタン菌ほど取り扱いが難しくあ りません。細菌の取り扱いについて、訓練を少しでも受けた経験者 であれば、誰でも簡単に取り扱えます。 この応用として、コピー用紙を水素に変換することも研究されてい ます。
１７．コピー用紙を水素に変換する細菌
http://tag.ahs.kitasato-u.ac.jp/tag-wada/noframe/e017.htm
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Investigations of Burial Diagenesis in Carbonate Hydrocarbon Reservoir Rocks
http://journals.hil.unb.ca/index.php/gc/article/view/2707/3145
Hans G. Machel
Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada, T6G 2E3.
hans.machel@ualberta.ca
SUMMARY
Investigations of burial diagenesis are instrumental for hydrocarbon exploration and exploitation. A proper investigation of diagenesis, with the aim to assist in exploration for and exploitation of hydrocarbons, should follow the "6 -Step Process". Step 1 : facies analysis (including establishing the primary porosity and permeability distributions, and the "primary aquastratigraphy" - a term newly defined in this article); Step 2 : petrographic analyses (paragenetic sequence, mapping amounts and spatial distribution of diagenetic phases); Step 3 : geochemical analyses (isotopes, trace elements, fluid inclusions, etc.); Step 4 : burial history and paleohydrology; Step 5: integration with extant data (especially petrophysical data), if available, and Step 6 : modeling (not necessary, but desirable in at least some cases). Diagenesis, at any depth from near-zero to several kilometres, is governed by various intrinsic and extrinsic factors that include thermodynamic and kinetic constraints, as well as microstructural factors. These factors govern diagenetic processes such as cementation, dissolution, compaction, recrystallization, replacement, and sulfate-hydrocarbon redox-reactions. Cementation, dissolution, and dolomitization require significant flow of groundwater (of whatever type and/or salinity, ranging from fresh to hypersaline), driven by an externally imposed hydraulic gradient. Other processes, such as stylolitization and thermochemical sulfate reduction, commonly take place without significant groundwater flow in hydrologically stagnant systems that are geochemically closed. Two effects of diagenesis that are especially important for hydrocarbon reservoirs are enhancement and/or reduction of porosity and permeability. However, these rock properties can also remain essentially unchanged through diagenesis at depths from near-zero to several kilometres. In extreme cases, an aquifer or hydrocarbon reservoir rock can have highly enhanced porosity and permeability because of extensive mineral dissolution, or it can be plugged up by extensive mineral precipitation.
SUMMAIRE
Les études de diagenèse d'enfouissement sont des instruments essentiels dans les domaines de l'exploration et de l'exploitation des hydrocarbures. Une étude de la diagenèse ayant comme objectif de contribuer à l'exploration et l'exploitation des hydrocarbures devrait suivre le processus suivant en six étapes : Étape1) L'analyse des faciès (comportant la mesure de la distribution de la porosité et de la perméabilité initiales, ainsi que de l'" aqua-stratigraphie " - terme redéfini dans le présent article; Étape 2) Les analyses pétrographiques (séquence paragénétique, cartographie de la répartition volumique et spatiale des différentes phases diagénétiques); Étape 3) Les analyses géochimiques (isotopiques, d'éléments traces, des inclusions fluides, etc.); Étape 4) L'historique d'enfouissement et la paléohydrologie; Étape 5) L'intégration avec les données existantes (particulièrement les données pétrophysiques), et Étape 6) La modélisation (pas nécessaire mais utile dans certains cas). Qu'il s'agisse de très faibles profondeurs ou de profondeurs de plusieurs kilomètres, la diagenèse est un phénomène qui est déterminé par des facteurs intrinsèques et extrinsèques, incluant des facteurs thermodynamiques et cinétiques, ainsi que microstructuraux. Ces facteurs déterminent des processus diagénétiques comme la cimentation, la dissolution, la compaction, la recristallisation, la substitution, ainsi que les réactions d'oxydoréduction sulfate-hydrocarbures. La cimentation, la dissolution et la dolomitisation suppose la circulation de volumes considérables d'eaux souterraines (peu importe le type et ou la salinité, qu'elles soient douces ou hyper-salines), mobilisés par les gradients hydrauliques ambiants. D'autres processus comme la stylolitisation et la réduction thermochimique des sulfates, se produisent généralement sans apport substantiel en eau dans le contexte de systèmes hydrologiques stagnants et géochimiques clos. La bonification et ou la détérioration de la porosité et de la perméabilité sont deux des effets diagénétiques particulièrement importants dans la caractérisation des réservoirs d'hydrocarbures. Cependant, ces propriétés lithologiques peuvent demeurer presqu'inchangées par la diagenèse qu'elle se produise à des profondeurs faibles ou de plusieurs kilomètres. Dans les cas limites, un aquifère ou un réservoir d'hydrocarbures peut comporter des porosités et des perméabilités qui auront été grandement bonifiées par l'action d'une dissolution minérale importante, ou voir leurs pores colmatés par l'action d'une précipitation minérale importante.
INTRODUCTION
1 Exploration for hydrocarbons is, first and foremost, the search for rocks with high porosity and permeability. These two basic petrophysical properties control almost all other hydrocarbon reservoir properties. Most importantly, the higher the porosity and permeability, the higher the chances for economically viable oil and gas storage, and for high flow rates during exploitation.
2 Porosity and permeability are originally controlled by sedimentary conditions at the time of deposition, and then modified by diagenetic alteration. In rocks that have not been buried deeply and/or that are relatively young, the reservoir properties are governed largely by depositional and facies parameters, such as water energy, grain size distribution, grain packing density, sorting and rounding, reef framework, etc. Overall, however, such reservoir rocks are in a minority. Most sediments and sedimentary rocks have been buried to several hundreds or thousands of meters for millions of years, with or without subsequent uplift. Commonly, the reservoir properties of such rocks are controlled by diagenesis because, with few exceptions, the effects of diagenesis increase with burial depth and time. Hence, investigations of diagenesis are instrumental for hydrocarbon exploration and exploitation, especially in deep basins.
3 Regardless of depth, investigations of diagenesis must take into account the conditions during and right after deposition, which determine the types and amounts of primary porosity and the chemistry of the pore water that may or may not have been buried with the sediments/rocks. These conditions are encompassed by the concept of "primary aquastratigraphy", as defined further below. The focus of this article, however, is on burial diagenesis, and especially on carbonates that may act as petroleum reservoir rocks. Fortunately, many if not most of the phenomena covered herein are valid for and/or applicable to both carbonates and clastics. Moreover, carbonate diagenesis cannot be treated fully without considering other rock types because of the chemical intercommunication of all rock types via hydrologic flow.
4 This article is geared primarily to individuals, students as well as professionals, who are relatively new to carbonate diagenesis and petroleum reservoir rocks. It provides an overview of the most relevant investigative methods and provides a ‘ cookbook recipe' for investigations of diagenesis (the so-called "6 - Step Process"). The ultimate goal of this paper is to aid reservoir characterization, especially the present porosity and permeability distribution that can be used in the development of hydrocarbon reservoirs by production engineers, as well as in exploration in terms of prediction of porosity and permeability.
1 Exploration for hydrocarbons is, first and foremost, the search for rocks with high porosity and permeability. These two basic petrophysical properties control almost all other hydrocarbon reservoir properties. Most importantly, the higher the porosity and permeability, the higher the chances for economically viable oil and gas storage, and for high flow rates during exploitation.
2 Porosity and permeability are originally controlled by sedimentary conditions at the time of deposition, and then modified by diagenetic alteration. In rocks that have not been buried deeply and/or that are relatively young, the reservoir properties are governed largely by depositional and facies parameters, such as water energy, grain size distribution, grain packing density, sorting and rounding, reef framework, etc. Overall, however, such reservoir rocks are in a minority. Most sediments and sedimentary rocks have been buried to several hundreds or thousands of meters for millions of years, with or without subsequent uplift. Commonly, the reservoir properties of such rocks are controlled by diagenesis because, with few exceptions, the effects of diagenesis increase with burial depth and time. Hence, investigations of diagenesis are instrumental for hydrocarbon exploration and exploitation, especially in deep basins.
3 Regardless of depth, investigations of diagenesis must take into account the conditions during and right after deposition, which determine the types and amounts of primary porosity and the chemistry of the pore water that may or may not have been buried with the sediments/rocks. These conditions are encompassed by the concept of "primary aquastratigraphy", as defined further below. The focus of this article, however, is on burial diagenesis, and especially on carbonates that may act as petroleum reservoir rocks. Fortunately, many if not most of the phenomena covered herein are valid for and/or applicable to both carbonates and clastics. Moreover, carbonate diagenesis cannot be treated fully without considering other rock types because of the chemical intercommunication of all rock types via hydrologic flow.
4 This article is geared primarily to individuals, students as well as professionals, who are relatively new to carbonate diagenesis and petroleum reservoir rocks. It provides an overview of the most relevant investigative methods and provides a ‘ cookbook recipe' for investigations of diagenesis (the so-called "6 - Step Process"). The ultimate goal of this paper is to aid reservoir characterization, especially the present porosity and permeability distribution that can be used in the development of hydrocarbon reservoirs by production engineers, as well as in exploration in terms of prediction of porosity and permeability.
METHODS OF INVESTIGATION
5 The various diagenetic processes and their effects on porosity and permeability can be investigated and/or characterized by a variety of methods that fall into two major groups (Fig. 1). The present group is used to establish present porosity and permeability, whereas the past group is used to establish past porosity and permeability and/or the evolution of these parameters through time.
6 There are two important aspects to the present group. First, this group covers all orders of magnitude from satellite images to microprobe spot analyses, at least in principle. In the petroleum industry, data from seismic, outcrop and/or core are almost always available, as are data from thin sections and the various microscopic methods of investigation. Hence, these are the standard tools by which the spatial distribution and sizes of pore spaces are determined. However, the various types of remote sensing and/or GIS have limited, albeit in some cases highly useful, applicability. For example, Harris and Kowalik (1994) have shown how the present distributions of porosity and permeability can be estimated from a series of satellite images of areas that are recent analogs to certain types of sedimentary hydrocarbon traps. This type of analysis can only be used when suitable satellite images are available, and when the sedimentary environment of interest in a given hydrocarbon play has a recent analog that can be imaged from outer space. Similarly, other types of remote sensing, such as aeromagnetics, gravity, etc., have limited applicability.
7 The present group of methods is further divided into two subgroups, i.e., those methods that are qualitative and/or semiquantitative, and those that are quantitative. The first subgroup, to the left of the vertical dotted line in Figure 1, characterizes the spatial distribution and sizes of porosity and permeability, whereas the second subgroup determines absolute amounts. Microbeam techniques (imaging, trace elements, isotopes) straddle this line, and thin section petrography and image analysis connect the two subgroups. Thin section, SEM, and microprobe images can be used to quantify the amounts of diagenetic phases and porosity (e.g., Weidlich et al., 1993; Fagerstrom and Weidlich, 1999). Petrophysical methods of investigation, i.e., mercury injection capillary pressure measurements, as well as direct porosimetry and permeability measurements on whole core or core plug samples can also be used effectively in the context of diagenetic investigations because they are quantitative (e.g., Luo and Machel, 1995; Lucia, 2000).
Figure 1. Methods of investigation of present and past porosity and permeability.
8 The past group of methods (Fig. 1) is composed of most of the standard tools of diagenetic investigation on microscopic and submicroscopic scales, including inorganic and organic geochemistry, as well as various types of modeling (burial history, paleohydrology, etc.). One should not expect unequivocal answers from any method. Rather, each method has the potential to reveal certain aspects of a rock's past, or its evolution through time. Unfortunately, some methods may fail to work in a given study. For example, fluid inclusion analysis may fail to provide reliable maximum burial temperatures because the inclusions are too small, or modeling of paleofluid flow may fail because the paleopermeability cannot be estimated with reasonable accuracy.
DIAGENETIC SETTINGS
9 The realm of diagenesis comprises all mineralogical, physical, and chemical changes of sedimentary deposits between the time of ultimate deposition and the onset of metamorphism (green-schist facies). Diagenetic settings are commonly divided into "shallow," "intermediate," and "deep" burial types; yet in many case studies these terms are ill-defined and hydrological/hydrogeochemical criteria are commonly ignored (a noteworthy exception is Galloway and Hobday, 1983). For these reasons, Machel (1999) proposed a new classification that is based on a critical synopsis of previous classifications and is applicable to all rock types (Fig. 2). This classification uses mineralogic, geochemical, and hydrogeologic criteria from clastic and carbonate rocks, the occurrence of hydrocarbons, and fractures. It differentiates near-surface, shallow-, intermediate-and deep-burial diagenetic settings, hydrocarbon-contaminated plumes, and fractures.
Petroliferous (Hydrocarbon-Bearing) Plumes
15 Petroliferous (hydrocarbon-contaminated) plumes, which originate from leaking oil and gas traps, represent a special type of diagenetic setting that may crosscut all previously defined settings. The escaping hydrocarbons tend to form subvertical plumes of moderately to strongly reducing conditions. The plumes tend to facilitate diagenetic reactions that are absent, or at least much less pronounced, outside the plumes, such as the formation of magnetic mineral assemblages, of carbonate cements with distinctive cathodoluminescence and/or isotopic composition, soil gas anomalies, distinctive vegetation, and a number of other phenomena (Barker et al., 1991; Burton et al., 1993; Al-Shaieb et al., 1994; Machel, 1995; Tedesco, 1995; Schumacher and Abrams, 1996).
Fractures
16 Another special type of diagenetic setting is fractures, which may be restricted to one of the diagenetic settings defined above or may transgress two or more of them. In the first case, diagenesis within the fractures is generally similar to that within the adjacent pore network. In the latter case, diagenesis within the fractures may be significantly different from that in the adjacent wall rocks, depending on how fast the waters/fluids move through the fractures, and whether these waters/fluids are significantly warmer, colder, underpressured, or overpressured relative to those in the wall rocks.
Temporal Designations
17 A paragenetic sequence lists diagenetic processes in the chronological order that they affected the rocks under investigation. The various processes are commonly given temporal designations, such as "early" or "late". However, such temporal designations are only relative and generally meaningless hydrogeochemically. For example, a "late-diagenetic" 16th phase in a complicated series of 18 phases may have formed in a near-surface setting from meteoric water perhaps only a few tens to hundreds of thousands of years after deposition, which is not uncommon in Cenozoic carbonates (e.g., Schroeder and Purser, 1986). Alternatively, a relatively "early-diagenetic" 5th phase may have formed at a depth of nearly 3 km some 300 m.y. after deposition, which is common in Paleozoic carbonates where the truly early diagenetic phases, those that formed during shallow burial, are obliterated and/or rendered unrecognizable by pervasive recrystallization (e.g., Schroeder and Purser, 1986). Hence, temporal designations should be used only in conjunction with the diagenetic settings shown in Figure 2.
9 The realm of diagenesis comprises all mineralogical, physical, and chemical changes of sedimentary deposits between the time of ultimate deposition and the onset of metamorphism (green-schist facies). Diagenetic settings are commonly divided into "shallow," "intermediate," and "deep" burial types; yet in many case studies these terms are ill-defined and hydrological/hydrogeochemical criteria are commonly ignored (a noteworthy exception is Galloway and Hobday, 1983). For these reasons, Machel (1999) proposed a new classification that is based on a critical synopsis of previous classifications and is applicable to all rock types (Fig. 2). This classification uses mineralogic, geochemical, and hydrogeologic criteria from clastic and carbonate rocks, the occurrence of hydrocarbons, and fractures. It differentiates near-surface, shallow-, intermediate-and deep-burial diagenetic settings, hydrocarbon-contaminated plumes, and fractures.
Near-Surface Diagenetic Settings
10 Near-surface diagenetic settings are those within a few metres of surface, where the pore fluids are essentially unaltered and of meteoric, brackish, marine, or evaporitic origin. Marine diagenetic settings, which can be subdivided into various subsettings (e.g., James and Choquette, 1990), are included here because of the significant marine diagenesis many carbonates experience before they are buried beyond the reach of surface-derived groundwaters. The hydrologic drives in near-surface settings vary from place to place; they include wind action, wave action, and tidal pumping in marine settings; density-driven reflux in evaporitic settings; and gravity drive in vadose/meteoric settings.
10 Near-surface diagenetic settings are those within a few metres of surface, where the pore fluids are essentially unaltered and of meteoric, brackish, marine, or evaporitic origin. Marine diagenetic settings, which can be subdivided into various subsettings (e.g., James and Choquette, 1990), are included here because of the significant marine diagenesis many carbonates experience before they are buried beyond the reach of surface-derived groundwaters. The hydrologic drives in near-surface settings vary from place to place; they include wind action, wave action, and tidal pumping in marine settings; density-driven reflux in evaporitic settings; and gravity drive in vadose/meteoric settings.
Shallow-Burial Diagenetic Settings
11 Shallow-burial diagenetic settings (also called shallow subsurface settings or environments) are similar in many respects, including hydrogeochemistry, to near-surface diagenetic settings. Important differences include physical compaction and hydrologic conditions that may vary with the (paleo-) geographic setting. For example, much if not most, pore-water flow at very shallow depths is facilitated by tidal pumping in marine settings, giving way to compaction with increasing depth. In coastal mixing zones, pore water throughput is facilitated by the convergence of two forces, gravity (topography) drive from meteoric water and density drive from seawater. In evaporitic settings, most fluid throughput is via density-driven reflux. Subaerially exposed settings are generally governed by gravity drive in local groundwater flow systems that respond to surface conditions such as weather, seasons, and latitude; all have local groundwater flow systems. An important exception, from a hydrogeochemical point of view, is where local and regional groundwater discharge areas merge, and where deep(er) groundwaters mix with shallow groundwaters, providing for special hydrogeochemical settings.
11 Shallow-burial diagenetic settings (also called shallow subsurface settings or environments) are similar in many respects, including hydrogeochemistry, to near-surface diagenetic settings. Important differences include physical compaction and hydrologic conditions that may vary with the (paleo-) geographic setting. For example, much if not most, pore-water flow at very shallow depths is facilitated by tidal pumping in marine settings, giving way to compaction with increasing depth. In coastal mixing zones, pore water throughput is facilitated by the convergence of two forces, gravity (topography) drive from meteoric water and density drive from seawater. In evaporitic settings, most fluid throughput is via density-driven reflux. Subaerially exposed settings are generally governed by gravity drive in local groundwater flow systems that respond to surface conditions such as weather, seasons, and latitude; all have local groundwater flow systems. An important exception, from a hydrogeochemical point of view, is where local and regional groundwater discharge areas merge, and where deep(er) groundwaters mix with shallow groundwaters, providing for special hydrogeochemical settings.
Intermediate- and Deep-Burial Diagenetic Settings
12 The lower limit of intermediate-burial diagenetic settings, and thereby the upper limit of deep-burial diagenetic settings, is defined as the top of the liquid oil window in hydrocarbon source rocks. This boundary is useful because the introduction of oil into the pore spaces commonly arrests mineral diagenesis. Unfortunately, the depth to the top of the oil window varies widely, i.e., between about 1500 and 4000 m depending on kerogen type and geothermal history, with a distribution maximum of about 2000 to 3000 m (Hunt, 1996). The latter depth interval is herewith taken as the bottom of intermediate-burial diagenetic settings. Deep-burial diagenetic settings merge into the metamorphic realm at temperatures around 200°C and commensurate depths and pressures, which depend on the geothermal gradient, e.g., about 6 km and 150 MPa (1.5 kbars) at 30°C/km, or about 9 km and 225 MPa(2.25 kbars) at 20°C/km (Winkler, 1979).
Figure 2. Classification of diagenetic settings on the basis of mineralogy, petroleum, hydrogeochemistry, and hydrogeology. For illustrative simplicity, the geologic section is assumed to be isotropic and homogeneous, with idealized groundwater flow lines. The hydrocarbon-contaminated plume is slightly deflected by the local and regional groundwater flow systems. The depth limits separating the burial diagenetic settings are approximate and based on geologic phenomena that are easily recognizable. Near-surface settings may be meteoric, brackish, marine, or hypersaline. Adapted from Machel (1999).
Display large image of Figure 2
13 The vast majority of sedimentary rocks spend most of their existence in the intermediate- and deep-burial realms, where porosity and permeability are commonly altered significantly, and where hydrocarbon maturation, migration, and most trapping occur. The associated groundwaters (also called burial fluids, formation fluids, subsurface brines, etc.) have compositions that are largely or entirely controlled by rockwater interactions.
14 In immature basins, the predominant hydrologic drive is compaction. In mature basins, intermediate- and deep-burial diagenetic settings are located within intermediate or regional ground-water flow systems (sensu Tóth, 1963; Lovley and Chapelle, 1995). Rocks in intermediate-burial settings experience chemical compaction as well as subsurface cementation and dissolution.
12 The lower limit of intermediate-burial diagenetic settings, and thereby the upper limit of deep-burial diagenetic settings, is defined as the top of the liquid oil window in hydrocarbon source rocks. This boundary is useful because the introduction of oil into the pore spaces commonly arrests mineral diagenesis. Unfortunately, the depth to the top of the oil window varies widely, i.e., between about 1500 and 4000 m depending on kerogen type and geothermal history, with a distribution maximum of about 2000 to 3000 m (Hunt, 1996). The latter depth interval is herewith taken as the bottom of intermediate-burial diagenetic settings. Deep-burial diagenetic settings merge into the metamorphic realm at temperatures around 200°C and commensurate depths and pressures, which depend on the geothermal gradient, e.g., about 6 km and 150 MPa (1.5 kbars) at 30°C/km, or about 9 km and 225 MPa(2.25 kbars) at 20°C/km (Winkler, 1979).
Figure 2. Classification of diagenetic settings on the basis of mineralogy, petroleum, hydrogeochemistry, and hydrogeology. For illustrative simplicity, the geologic section is assumed to be isotropic and homogeneous, with idealized groundwater flow lines. The hydrocarbon-contaminated plume is slightly deflected by the local and regional groundwater flow systems. The depth limits separating the burial diagenetic settings are approximate and based on geologic phenomena that are easily recognizable. Near-surface settings may be meteoric, brackish, marine, or hypersaline. Adapted from Machel (1999).
Display large image of Figure 2
13 The vast majority of sedimentary rocks spend most of their existence in the intermediate- and deep-burial realms, where porosity and permeability are commonly altered significantly, and where hydrocarbon maturation, migration, and most trapping occur. The associated groundwaters (also called burial fluids, formation fluids, subsurface brines, etc.) have compositions that are largely or entirely controlled by rockwater interactions.
14 In immature basins, the predominant hydrologic drive is compaction. In mature basins, intermediate- and deep-burial diagenetic settings are located within intermediate or regional ground-water flow systems (sensu Tóth, 1963; Lovley and Chapelle, 1995). Rocks in intermediate-burial settings experience chemical compaction as well as subsurface cementation and dissolution.
Petroliferous (Hydrocarbon-Bearing) Plumes
15 Petroliferous (hydrocarbon-contaminated) plumes, which originate from leaking oil and gas traps, represent a special type of diagenetic setting that may crosscut all previously defined settings. The escaping hydrocarbons tend to form subvertical plumes of moderately to strongly reducing conditions. The plumes tend to facilitate diagenetic reactions that are absent, or at least much less pronounced, outside the plumes, such as the formation of magnetic mineral assemblages, of carbonate cements with distinctive cathodoluminescence and/or isotopic composition, soil gas anomalies, distinctive vegetation, and a number of other phenomena (Barker et al., 1991; Burton et al., 1993; Al-Shaieb et al., 1994; Machel, 1995; Tedesco, 1995; Schumacher and Abrams, 1996).
Fractures
16 Another special type of diagenetic setting is fractures, which may be restricted to one of the diagenetic settings defined above or may transgress two or more of them. In the first case, diagenesis within the fractures is generally similar to that within the adjacent pore network. In the latter case, diagenesis within the fractures may be significantly different from that in the adjacent wall rocks, depending on how fast the waters/fluids move through the fractures, and whether these waters/fluids are significantly warmer, colder, underpressured, or overpressured relative to those in the wall rocks.
Temporal Designations
17 A paragenetic sequence lists diagenetic processes in the chronological order that they affected the rocks under investigation. The various processes are commonly given temporal designations, such as "early" or "late". However, such temporal designations are only relative and generally meaningless hydrogeochemically. For example, a "late-diagenetic" 16th phase in a complicated series of 18 phases may have formed in a near-surface setting from meteoric water perhaps only a few tens to hundreds of thousands of years after deposition, which is not uncommon in Cenozoic carbonates (e.g., Schroeder and Purser, 1986). Alternatively, a relatively "early-diagenetic" 5th phase may have formed at a depth of nearly 3 km some 300 m.y. after deposition, which is common in Paleozoic carbonates where the truly early diagenetic phases, those that formed during shallow burial, are obliterated and/or rendered unrecognizable by pervasive recrystallization (e.g., Schroeder and Purser, 1986). Hence, temporal designations should be used only in conjunction with the diagenetic settings shown in Figure 2.
POROPERM REDUCTION, PRESERVATION, AND ENHANCEMENT
18 Porosity and permeability (poroperm) can be reduced, preserved, or enhanced through diagenesis. Figure 3 illustrates this phenomenon and the controlling factors for the well-studied Cenozoic limestones and dolostones from Florida and the Jurassic Smackover oolite reservoirs in the southern United States. Even though the trends are generally toward porosity reduction with depth, some Smackover rocks have much higher, others much lower, porosities than the average. Permeabilities are assumed to decrease with decreasing porosities. Although comparable permeability/ depth data sets are not available from these studies, they are available from studies of dolomitization. Commonly permeability increases along with porosity, and vice versa. This is documented through studies from the Late Devonian Grosmont Formation in eastern Alberta (Luo et al., 1994; Luo and Machel, 1995; Machel and Huebscher, 2000) and from the Cambrian-Ordovician Bonneterre Formation of Missouri, USA., which is host to one of the world's largest MVT-sulfide deposits (Woody et al., 1996). In both cases, there are significant positive correlations between porosity and permeability.
19 Based on this evidence, the porosity and permeability distribution in Cenozoic limestones and dolostones from Florida and the Jurassic Smackover rocks can be considered typical for many if not most carbonate rocks elsewhere. Their vertical distribution apparently can be highly variable, depending on the relative importance of the various processes involved. These processes begin syndepositionally and are governed by a number of intrinsic and extrinsic factors.
Intrinsic and Extrinsic Factors
20 Diagenetic processes that affect porosity and permeability in any type of sedimentary rock are cementation, dissolution, compaction, recrystallization, replacement (in carbonates, predominantly dolomitization), and sulfatehydrocarbon redox-reactions. To be volumetrically significant, cementation, dissolution, and dolomitization require significant flow of groundwater driven by an externally imposed hydraulic gradient because of the relatively low aqueous solubilities of almost all minerals. Other processes can and commonly do take place without significant groundwater flow, or even in hydrologically stagnant and consequently geochemically "closed" systems. Physical compaction is intermediate between these two groups. Physical compaction is not stagnant, as it generates flow, but it does not require an externally imposed driving force other than sedimentary loading.
21 The above diagenetic processes are governed by several factors including increasing temperature and pressure with depth, chemical changes in the pore fluids, and various types of groundwater flow (e.g., Hanor, 1987, 1994). The rocks influence, and are affected by, these factors – an interplay that is commonly called "water-rock interaction".
22 As far as these factors are concerned, diagenesis of one rock type cannot be separated from the diagenesis of other rock types, especially in intermediate- to deep-burial settings, where intercommunication of all rock types by groundwater flow is common. Nowhere is this more obvious than in the case of subsurface dissolution. Many carbonates have secondary porosity from dissolution in diagenetic burial settings, and most processes that generate acids originate in, or are facilitated by, clastic and carbonaceous rocks (e.g., Giles and Marshall, 1986; Surdam et al., 1989).
Thermodynamic Constraints
23 Cementation and dissolution are governed mainly by the saturation state. In general, temperature, pressure, and composition of the groundwater(s) determine the saturation state(s) and, hence, precipitation and dissolution, either directly or indirectly in one or several ways.
- Pore fluids in sedimentary basins, if buried and not changed significantly through water-rock interaction or mixing, become supersaturated with respect to carbonates and sulfates with depth, even if the concentrations of the cations (calcium, magnesium, iron, etc.) and carbonate ions remain essentially unchanged. Conversely, ascending formation/ groundwaters that cool tend to become undersaturated with respect to carbonates and sulfates, with the potential to generate significant secondary porosity in carbonates and/or clastics that contain carbonate cements (e.g., Giles and deBoer, 1989). The reverse is true for silicates and most other mineral groups. This is because of the temperature-dependent retrograde and prograde solubility of carbonates and sulfates versus silicates and other mineral groups, respectively.
- The concentrations of the cations and carbonate ions in solution generally increase because of pressure solution and/or a variety of diagenetic reactions involving non-carbonate minerals, such as silicates and sulfates. A common result is precipitation of carbonates because of the common-ion effect (e.g., Hanor, 1987).
- An increase in acidity can take place in many ways, including meteoric water penetration, mixing of waters, carbon dioxide generation from maturation of organic matter, generation of organic acids, and formation of acids from clay mineral reactions (e.g., Giles and Marshall, 1986); it leads to carbonate dissolution.
- Mixing of groundwaters may lead to pronounced undersaturation or supersaturation with respect to carbonate minerals, depending on temperature, pressure, and fluid composition, particularly pCO2 of the mixed water. Mixing of shallow groundwaters at relatively low temperatures commonly results in under-saturation and dissolution, which is well known from karst terrains (e.g., Bonacci, 1987; James and Choquette, 1987; Smart et al., 1988) and from caves in coastal seawater-freshwater mixing zones (e.g., Machel and Mountjoy, 1990). However, mixing of fresh groundwater with brine in deep burial settings commonly leads to supersaturation and carbonate precipitation (Morse et al., 1997).
- Pressure decreases, with or withouta significant temperature decrease, almost invariably leads to carbonate supersaturation and precipitation (Morse et al., 1997), either because of reverse solubility, CO2 -degassing, or both.
24 Under the assumption that minerals and solutions attain local thermodynamic equilibrium along the flow path, the above processes can be quantified in computer simulations to predict the precipitation and dissolution of diagenetic minerals along the flow path in basin strata as groundwaters migrate along temperature and pressure gradients. Using this approach, rock porosity evolution can be calculated from relative amounts of mineral precipitation and dissolution (e.g., Lee, 1997; Morse et al., 1997). Permeability changes, however, can merely be inferred, as pore throat sizes and tortuosity cannot be predicted from thermodynamics.
Figure 3. Major processes of porosity and permeability ("poroperm") generation, preservation, and reduction in carbonates. The inset contains averaged porosity/depth data from limestones and dolostones in south Florida (dashed line beginning at about 40% near the surface - from Schmoker and Halley, 1982) and Smackover oolitic carbonate reservoirs in the southern United States (solid lines that represent the measured maximum and minimum values below depths of about 1.5 km are from Scholle and Halley, 1985, and Heydari, 1997). The Florida trend can be considered typical for most carbonates elsewhere. The large variations in Smackover carbonates at any given depth reflect highly variable degrees of porosity generation, preservation, and reduction.
Display large image of Figure 3
Diagenetic Potential and Kinetic Factors
25 Both carbonates and clastics have different diagenetic potentials during burial, i.e., in any diagenetic setting certain minerals or types of grains exist that dissolve, form, or recrystallize preferentially over others. Such phenomena are governed by textural and/or kinetic factors. One of the best known examples is that small grains dissolve more rapidly than large grains during recrystallization and/or Ostwald ripening (e.g., Folk, 1965; Morse and Casey, 1988). Another example of microstructural control is that aragonite with complex microstructures can dissolve more rapidly than thermodynamically less stable magnesian calcite (Walter, 1985). Kinetic factors can override thermodynamic constraints during precipitation, particularly in near-surface and shallow diagenetic settings. Examples include the well-known kinetic inhibition of dolomite formation from seawater, and the formation of ‘ protodolomite' rather than dolomite from evaporated groundwater or seawater (e.g., Machel and Mountjoy, 1986; Usdowski, 1994). Such kinetic problems are ignored in the remainder of this paper, however, under the assumption that most diagenetic settings have had enough time to adjust to a thermodynamic equilibrium mineral assemblage. This certainly is true for most intermediate- and deep-burial settings, where sudden incursions of "alien" formation fluids are relatively rare, and where flow rates are generally low, except in fracture systems.
26 Another important factor, especially in intermediate- and deep-burial settings, is that hydrocarbons commonly arrest diagenesis, either because they coat potentially reactive grain surfaces in oil-wet systems, or because the relative permeability to water is very low or zero in the case of high oil saturation in water-wet systems (e.g., Laudon, 1996). In both cases, ionic exchange through the aqueous phase (dissolution, precipitation), and hence diagenesis, is inhibited, except for local and volumetrically insignificant mineral redistribution by diffusion. However, some hydrocarbons may react with the rocks, as in the case of thermochemical sulfate reduction (discussed below).
Depositional Controls
27 In carbonates, much more so than in clastics, depositional environment and facies, especially cycle stacking patterns, play an important role in determining the porosity and permeability distribution and their subsequent evolution through burial diagenesis. A case in point is the Knox Group in Tennessee, which contains transgressive and regressice carbonate cycles (Montañez, 1997). The transgressive cycles, which originally were fairly porous and permeable, now consist of limestone and <10 to >50 vol% "late-diagenetic" dolomite having an average porosity of 8.2% and an average permeability of 70.2 md, which are interpreted to have formed during intermediate to deep burial. Petrographic data also show that these rocks were affected by extensive dissolution in intermediate- to deep-burial settings. However, the facies within regressive cycles are almost completely replaced by tight fine-crystalline dolomite that formed syn-depositionally from evaporated seawater. The transgressive carbonate cycles behaved like aquifers during later burial diagenesis, whereas the regressive cycles became aquitards almost syn-depositionally. Other examples of depositional control on diagenesis are reef and reef margin carbonates, which typically are much more porous and permeable than back-reef and deep fore-reef carbonates (e.g., Schneidermann and Harris, 1985; Schroeder and Purser, 1986). This commonly leads to a pronounced differentiation into "proto-aquifers" and "protoaquitards" at the time of deposition.
Near-Surface Settings
Marine Diagenesis
28 Most carbonate rocks originate as marine sediments having primary porosities around 40-45%. Hence, the first pore water to affect the carbonate sediments is seawater, and the diagenetic setting is near-surface marine, where the predominant hydrologic drives are wind/wave action and tidal pumping. The main effect is partial to extensive filling of primary pores with internal sediments and marine carbonate cements (James and Choquette, 1990), which leads to significant porosity reduction. In general, highly porous and permeable facies types affected by vigorous waves and tides tend to become more cemented than other facies types in hydrogeologically less vigorous settings. Recrystallization of metastable aragonite and magnesian calcites also occurs, but this generally has little effect on porosity/permeability development.
28 Most carbonate rocks originate as marine sediments having primary porosities around 40-45%. Hence, the first pore water to affect the carbonate sediments is seawater, and the diagenetic setting is near-surface marine, where the predominant hydrologic drives are wind/wave action and tidal pumping. The main effect is partial to extensive filling of primary pores with internal sediments and marine carbonate cements (James and Choquette, 1990), which leads to significant porosity reduction. In general, highly porous and permeable facies types affected by vigorous waves and tides tend to become more cemented than other facies types in hydrogeologically less vigorous settings. Recrystallization of metastable aragonite and magnesian calcites also occurs, but this generally has little effect on porosity/permeability development.
Coastal Mixing Zone Diagenesis
29 In coastal areas where seawater mixes with fresh water, the predominant diagenetic process affecting carbonate sediments and rocks is dissolution (Plummer, 1975). Groundwater fluxes in coastal mixing zones (also called "zones of dispersion") typically are quite high, and the effects are enhanced porosity and permeability, including caves, which are well known from many such settings. Other well known processes in coastal mixing zones are dolomite cementation and replacive dolomitization. However, the effects of these processes are volumetrically insignificant (less than 1 vol-%) in almost all cases (Machel and Mountjoy, 1990). Similarly, some coastal mixing zones form aragonite or calcite cements (Csoma and Goldstein, 2004), but mixing zone cementation is volumetrically negligible in most settings.
Meteoric Diagenesis
30 Meteoric waters in near-surface settings are almost always undersaturated with respect to carbonates because rain water is essentially devoid of earth alkali metals yet slightly acidic because of dissolved atmospheric CO2. Where the ground has a significant soil cover, pCO2 in the downward percolating rain water of the vadose zone can easily increase by two orders of magnitude because of extensive plant and microbial activity in the soil zone. This increase results in extensive dissolution in the upper few metres of burial, and the effects are increased porosity and permeability and/or physical weakness of the rocks. For example, in the Caribbean islands, many of which have a cover of Cenozoic carbonates that have not been buried by more than a few metres, the rocks are frail and crumbly because of a lack of near-surface cementation and/or subsequent meteoric dissolution (James and Choquette, 1984).
Hypersaline Diagenesis
31 The only volumetrically important and widespread diagenetic effect of ground-water flow on carbonates in near-surface evaporitic settings is reflux dolomitization. Typically, fresh groundwater and/or seawater that are evaporated to or beyond gypsum saturation flow seaward within the uppermost few metres of the carbonate sediments via density-drive. These fluids form finely crystalline and geochemically distinct dolomite, either as a replacement or as cement. The resulting dolostones typically are laterally extensive, yet thin, aquitards that may form effective seals for hydrocarbon trapping (e.g., Machel and Mountjoy, 1986; Moore and Wilde, 1986).
Shallow-Burial Settings
32 The four near-surface hydrogeochemical settings discussed above (marine, brackish, meteoric, and hypersaline) commonly persist into shallow-burial diagenetic settings, where physical compaction and, at greater depths, incipient chemical compaction, as well as a relatively minor amount of water-rock interaction occur. The major differences compared to near-surface settings are that deeper meteoric settings generally experience cementation and porosity/permeability loss rather than dissolution and porosity/permeability gain.
Physical (Mechanical) Compaction
33 With increasing burial, physical (mechanical) compaction leads to loss of water and porosity. Carbonate sediments can compact to about one-half of their original thickness under as little as 100 m of overburden by physical compaction alone (Choquette and James, 1987, 1990). Thereby, sedimentary particles and structures are modified and rearranged until a self-supporting framework is achieved at an average porosity of about 40%. Further burial will lead to grain deformation in the form of ductile (squeezing) or brittle (breakage) failure, followed by chemical compaction. Common textures generated by mechanical compaction include thinning of laminae between, and draping over, concretions; flattening of burrows, fenestrae, gas-escape structures, desiccation cracks, and skeletal or detrital grains; rotated grains; spalling of coated grains; swirling structures; telescoping (conversion of grain-poor to grain-supported textures); and planar to curviplanar grain contacts. In contrast to most other diagenetic processes and effects, the extent of physical compaction and concurrent porosity/permeability loss strongly depends on depositional setting and near-surface diagenesis. Specifically, shallow-water carbonates generally become strongly cemented and solidified in the near-surface marine setting, which inhibits later physical compaction. However, cementation is typically poor in deep-marine carbonates, such as chalks, which permit much more extensive physical compaction during burial (e.g., Choquette and James, 1987, 1990; Maliva and Dickson, 1992).
33 With increasing burial, physical (mechanical) compaction leads to loss of water and porosity. Carbonate sediments can compact to about one-half of their original thickness under as little as 100 m of overburden by physical compaction alone (Choquette and James, 1987, 1990). Thereby, sedimentary particles and structures are modified and rearranged until a self-supporting framework is achieved at an average porosity of about 40%. Further burial will lead to grain deformation in the form of ductile (squeezing) or brittle (breakage) failure, followed by chemical compaction. Common textures generated by mechanical compaction include thinning of laminae between, and draping over, concretions; flattening of burrows, fenestrae, gas-escape structures, desiccation cracks, and skeletal or detrital grains; rotated grains; spalling of coated grains; swirling structures; telescoping (conversion of grain-poor to grain-supported textures); and planar to curviplanar grain contacts. In contrast to most other diagenetic processes and effects, the extent of physical compaction and concurrent porosity/permeability loss strongly depends on depositional setting and near-surface diagenesis. Specifically, shallow-water carbonates generally become strongly cemented and solidified in the near-surface marine setting, which inhibits later physical compaction. However, cementation is typically poor in deep-marine carbonates, such as chalks, which permit much more extensive physical compaction during burial (e.g., Choquette and James, 1987, 1990; Maliva and Dickson, 1992).
Intermediate- to Deep-Burial Settings
Chemical Compaction
34 Chemical compaction results from pressure solution that is caused by load or tectonic stress at grain contacts, because stress increases mineral solubility. In addition, clay minerals embedded in the carbonate matrix may enhance or reduce the carbonate solubility (depending on the types of clays and their composition). Other factors that influence the inception and course of pressure solution include the burial depth, pore water composition, mineralogy, and the presence or absence of organic matter (including oil and gas). Depending on the interaction of these factors, pressure solution in carbonates commonly begins perhaps within 200 to 300 m of burial, with the first microstylolites forming at minimum depths of ca. 500 m of burial (Lind, 1993; Fabricius, 2000). Where dolostones are associated with limestones, the latter tend to be more susceptible to pressure solution.
35 Pressure solution textures are diverse and include stylolites (one or several generations, typically with different amplitudes), other types of sutured seams, isolated or fitting nodules, nonsutured seams (Choquette and James, 1987, 1990), and pseudo-bedding that can resemble layering caused by sedimentary processes (Bathurst 1987; Munnecke et al., 2001; Fig. 4). Stylolites can be used to determine the number of burial episodes (number of generations) and the amount of compaction (calculations involve the number and amplitudes of stylolites: Bodou, 1976; Choquette and James, 1987, 1990; Ricken, 1987).
36 The type of interpenetration of adjacent grains during pressure solution depends on which minerals are juxtaposed. Where two grains are the same mineral, the pressure solution contact is sutured, as both grains dissolve to the same extent. However, the contacts are smooth where the mineralogy differs, as one mineral effectively grows at the expense of the other. For example, dolomite (mineral A) commonly grows into calcite (mineral B), and quartz commonly grows into calcite and/or dolomite, as illustrated in Figure 5. Such textures have been known for a long time, and the most common explanation given is that the solubility of mineral B is higher than that of mineral A at the contact point or surface. An alternative and more convincing explanation has been provided relatively recently by Fletcher and Merino (2001). These authors redefined and thereby expanded the principle of "force of crystallization" as "interfacial normal stress" (or "induced stress"). This stress is generated by growth driven by supersaturation of mineral A between crystals of minerals A and B, and the magnitude of this stress is dependent on the degree of supersaturation, temperature, as well as what the other mineral is. For example, at a temperature of 100 °C and a super-saturation of OMEGA = 2, quartz growing at the expense of calcite (quartz replacing calcite) generates a negligible stress, whereas calcite growing at the expense of quartz generates a huge stress of about 100 MPa (Fletcher and Merino, 2001). This effectively means that quartz penetrates calcite like a knife cutting into butter, as shown in Figure 5, where the pore water is supersaturated with respect to quartz yet saturated or undersaturated with respect to calcite. Conversely, calcite tends to deform or fracture adjacent quartz grains, if the pore water is supersaturated with respect to calcite yet saturated or undersaturated with respect to quartz. Both these scenarios are possible during pressure solution, depending on fluid composition. Figure 6 shows this and several other scenarios. Mineral pairs in the top left quadrant will show replacement textures, like "a knife cutting into butter", whereas the inverted mineral pairs in the bottom right quadrant will show deformation and/or brittle failure of the "weaker" mineral.
37 Chemical compaction begins during the latter phases of physical compaction and continues into the metamorphic realm (Choquette and James, 1987, 1990). Chemical compaction is most active in rocks that are being buried (as opposed to being stationary at some depth), and that have some porosity left to facilitate grain interpenetration and ionic movement from the points of dissolution into the pore fluids. The liberated ions move, via advection or diffusion, to areas of lower stress, either just adjacent to the area of dissolution or elsewhere in the pore system, where the dissolved material may reprecipitate, forming burial-diagenetic cements. Chemical compaction is known to result in thickness reductions of at least 25-35% in addition to the thickness losses caused by physical compaction. In the Smackover oolites, which were used to construct the porosity/depth curves in Figure 3, physical and chemical compaction combined account for a loss of 33% of the original 45% porosity (Heydari, 1997).
38 Chemical compaction generally is detrimental to reservoir rock characteristics and/or petroleum production. The major effects are porosity and permeability reduction as a result of the overall thickness reduction and reprecipitation of the material dissolved at grain contacts.
Figure 4. Pressure solution features in polished core samples. A: Anastomosing swarm of stylolites in limestone. The convergence, similar amplitudes, and similar thicknesses of these stylolites indicate that they formed during one pressure solution episode. Devonian limestone, Alberta, Canada. Width of photograph is 5 cm. B: High-amplitude stylolite where white calcite precipitated along many of its vertical limbs. This calcite is derived locally from dissolution of limestone close to the apices of the stylolite. Most white calcite fills tension gashes that formed in response to tri-axial stress. Devonian limestone, partially dolomitized, Alberta, Canada. Width of photograph is 5 cm. C: Very long, wedge-shaped tension gashes originating at stylolites in response to triaxial stress during pressure solution. Compared to the rock depicted in Figure 4B, these gashes do not contain cement. Such uncemented gashes form excellent permeability pathways. Devonian limestone, Alberta, Canada. Width of photograph is 5 cm. D: Nodular limestone with numerous pressure solution seams that separate domains consisting mostly of limestone from those consisting of calcareous shale. Many of the limestone domains are early-diagenetic calcite concretions that are partially dissolved along the pressure solution seams. Most rocks with such textures originated as compositionally and texturally homogeneous marly sediments. Devonian limestone, Alberta, Canada. Width of photograph is 6 cm.
Display large image of Figure 4
34 Chemical compaction results from pressure solution that is caused by load or tectonic stress at grain contacts, because stress increases mineral solubility. In addition, clay minerals embedded in the carbonate matrix may enhance or reduce the carbonate solubility (depending on the types of clays and their composition). Other factors that influence the inception and course of pressure solution include the burial depth, pore water composition, mineralogy, and the presence or absence of organic matter (including oil and gas). Depending on the interaction of these factors, pressure solution in carbonates commonly begins perhaps within 200 to 300 m of burial, with the first microstylolites forming at minimum depths of ca. 500 m of burial (Lind, 1993; Fabricius, 2000). Where dolostones are associated with limestones, the latter tend to be more susceptible to pressure solution.
35 Pressure solution textures are diverse and include stylolites (one or several generations, typically with different amplitudes), other types of sutured seams, isolated or fitting nodules, nonsutured seams (Choquette and James, 1987, 1990), and pseudo-bedding that can resemble layering caused by sedimentary processes (Bathurst 1987; Munnecke et al., 2001; Fig. 4). Stylolites can be used to determine the number of burial episodes (number of generations) and the amount of compaction (calculations involve the number and amplitudes of stylolites: Bodou, 1976; Choquette and James, 1987, 1990; Ricken, 1987).
36 The type of interpenetration of adjacent grains during pressure solution depends on which minerals are juxtaposed. Where two grains are the same mineral, the pressure solution contact is sutured, as both grains dissolve to the same extent. However, the contacts are smooth where the mineralogy differs, as one mineral effectively grows at the expense of the other. For example, dolomite (mineral A) commonly grows into calcite (mineral B), and quartz commonly grows into calcite and/or dolomite, as illustrated in Figure 5. Such textures have been known for a long time, and the most common explanation given is that the solubility of mineral B is higher than that of mineral A at the contact point or surface. An alternative and more convincing explanation has been provided relatively recently by Fletcher and Merino (2001). These authors redefined and thereby expanded the principle of "force of crystallization" as "interfacial normal stress" (or "induced stress"). This stress is generated by growth driven by supersaturation of mineral A between crystals of minerals A and B, and the magnitude of this stress is dependent on the degree of supersaturation, temperature, as well as what the other mineral is. For example, at a temperature of 100 °C and a super-saturation of OMEGA = 2, quartz growing at the expense of calcite (quartz replacing calcite) generates a negligible stress, whereas calcite growing at the expense of quartz generates a huge stress of about 100 MPa (Fletcher and Merino, 2001). This effectively means that quartz penetrates calcite like a knife cutting into butter, as shown in Figure 5, where the pore water is supersaturated with respect to quartz yet saturated or undersaturated with respect to calcite. Conversely, calcite tends to deform or fracture adjacent quartz grains, if the pore water is supersaturated with respect to calcite yet saturated or undersaturated with respect to quartz. Both these scenarios are possible during pressure solution, depending on fluid composition. Figure 6 shows this and several other scenarios. Mineral pairs in the top left quadrant will show replacement textures, like "a knife cutting into butter", whereas the inverted mineral pairs in the bottom right quadrant will show deformation and/or brittle failure of the "weaker" mineral.
37 Chemical compaction begins during the latter phases of physical compaction and continues into the metamorphic realm (Choquette and James, 1987, 1990). Chemical compaction is most active in rocks that are being buried (as opposed to being stationary at some depth), and that have some porosity left to facilitate grain interpenetration and ionic movement from the points of dissolution into the pore fluids. The liberated ions move, via advection or diffusion, to areas of lower stress, either just adjacent to the area of dissolution or elsewhere in the pore system, where the dissolved material may reprecipitate, forming burial-diagenetic cements. Chemical compaction is known to result in thickness reductions of at least 25-35% in addition to the thickness losses caused by physical compaction. In the Smackover oolites, which were used to construct the porosity/depth curves in Figure 3, physical and chemical compaction combined account for a loss of 33% of the original 45% porosity (Heydari, 1997).
38 Chemical compaction generally is detrimental to reservoir rock characteristics and/or petroleum production. The major effects are porosity and permeability reduction as a result of the overall thickness reduction and reprecipitation of the material dissolved at grain contacts.
Figure 4. Pressure solution features in polished core samples. A: Anastomosing swarm of stylolites in limestone. The convergence, similar amplitudes, and similar thicknesses of these stylolites indicate that they formed during one pressure solution episode. Devonian limestone, Alberta, Canada. Width of photograph is 5 cm. B: High-amplitude stylolite where white calcite precipitated along many of its vertical limbs. This calcite is derived locally from dissolution of limestone close to the apices of the stylolite. Most white calcite fills tension gashes that formed in response to tri-axial stress. Devonian limestone, partially dolomitized, Alberta, Canada. Width of photograph is 5 cm. C: Very long, wedge-shaped tension gashes originating at stylolites in response to triaxial stress during pressure solution. Compared to the rock depicted in Figure 4B, these gashes do not contain cement. Such uncemented gashes form excellent permeability pathways. Devonian limestone, Alberta, Canada. Width of photograph is 5 cm. D: Nodular limestone with numerous pressure solution seams that separate domains consisting mostly of limestone from those consisting of calcareous shale. Many of the limestone domains are early-diagenetic calcite concretions that are partially dissolved along the pressure solution seams. Most rocks with such textures originated as compositionally and texturally homogeneous marly sediments. Devonian limestone, Alberta, Canada. Width of photograph is 6 cm.
Display large image of Figure 4
Cementation
39 Cementation is common in intermediate- and deep-burial settings because of elevated temperatures, fluid mixing, and chemical compaction (see above). Cementation of several volume percent, which is common, requires large fluid fluxes, however, because the solubility of most carbonates is rather low (e.g., K = 10 -8.52 at 25°C for calcite, decreasing with increasing temperature, Robie et al., 1979). Nevertheless, numerous case studies have demonstrated extensive intermediate- and deep-burial cementation (and concurrent porosity/permeability losses) in carbonate aquifers, not only with carbonate minerals but also with sulfates, sulfides, and clay minerals (e.g., Scholle and Halley, 1985; Walls and Burrowes, 1985; Woronik and Land, 1985; several articles in Montañez et al., 1997). By contrast, some studies have shown deep burial cementation to be relatively minor (e.g., Prezbindowski, 1985).
40 Burial cements in carbonate rocks are mainly calcite, dolomite, and/or anhydrite, and they have a number of characteristics: (a) crystals cross-cut stylolites, or microstylolites and pressure solution seams terminate at cement crystals; (b) crystals occur in fractures or spalled ooid cortices; (c) crystals fill compacted pores; (d) crystals enclose compacted grains; (e) crystals contain hydrocarbons in fluid inclusions; (f) crystals partially replace earlier burial cements; (g) crystals have relatively large size (diameters from several tens of micrometres up to several centimetres); (h) crystals are ‘ blocky' and form equant mosaics, increase in mean diameter toward pore centres, or are poikilotopic (poikilitic); (i) crystals are not recrystallized; (j) carbonate crystals show well-defined cathodoluminescence zonation that ranges from bright towards quenched (dull), in some cases repeatedly, or they are dull-luminescent throughout, commonly caused by ferroan composition (divalent iron >500 ppm); (k) carbonate crystals have oxygen isotope ratios that are depleted relative to marine cements of the same stratigraphic age as the host rocks; and (l) crystals contain two-phase fluid inclusions with elevated temperatures of homogenization (>50°C) and large freezing point depressions (indicating high salinities). Characteristics (a) to (f) above are distinctive and indicate a burial origin (Figs. 7 and 8), but are relatively rare in some rocks. The other characteristics are not unique to burial diagenetic cements. Therefore, any interpretation of burial cementation should combine as many lines of evidence as possible.
Figure 5. Schematic representation of pressure solution contacts between grains of different ‘ pressure solution solubility'. Note that limestone grains are penetrated by dolomite and chert, dolomite is penetrated only by chert. Contacts between grains of equal ‘ solubility' tend to be serrated (stylolitic), contacts between grains of unequal ‘ solubility' tend to be smooth. Modified from Trurnit and Amstutz (1979).
Display large image of Figure 5
Figure 6. Schematic representation of pressure solution contacts depending on the induced stress at the crystal-crystal interface for several mineral pairs. The contours denote interfacial normal stress generated by growth driven by a supersaturation of OMEGA=2 for phase A (the first listed in any given pair) at T=100 °C. For details of the calculation procedure see Fletcher and Merino (2001). This figure is modified from their paper.
Display large image of Figure 6
Dissolution
41 Dissolution is common in intermediate-and deep-burial settings (albeit volumetrically it is not as important as cementation, or else a general porosity decrease with depth would not occur - see Figure 3), especially near the oil window where decarboxylation and certain other mineral reactions generate acidity. Secondary porosity is well known from carbonates (Choquette and Pray, 1970) and clastics (Schmidt and MacDonald, 1979). Significant dissolution may or may not involve large fluid fluxes. If acidity is generated within or near the rock with secondary porosity, large-scale pore water flow is not necessary.
42 A hitherto controversial process to generate secondary porosity in deep burial settings is thermochemical sulfate reduction (TSR). Model calculations suggest that partial dissolution of carbonate rocks may occur at least initially during TSR (Hutcheon, 1992; Nicholson, 1992), but most published case studies of TSR do not show a significant increase in porosity (e.g., Machel et al., 1995a). Dissolution via TSR, however minor, usually is an in situ process because TSR commonly takes place in hydrologically closed or nearly closed systems (e.g., Machel 2001).
Recrystallization
43 The matrix, allochems, and cements formed at shallow depths become thermodynamically metastable or unstable with increasing burial because of increasing temperature, pressure, and changing composition of the groundwaters. Barring kinetic inhibition, recrystallization and replacement of metastable and unstable minerals will occur. However, porosity and permeability are generally little affected by recrystallization.
Figure 7. Bladed to fibrous burial cements. A: Multiple generations of radiaxial fibrous calcite cement filling subvertical fracture. Compactional or tectonic stresses resulted in multiple micro-faulting roughly perpendicular to the orientation of the fracture. Devonian reef limestone, Germany. Width of photograph is 3 cm. B: Multiple generations of radiaxial fibrous calcite cement and internal sediment filling subvertical fracture. In this case, the fracture was completely filled by the cement but was re-opened, as indicated by the fragment of fibrous calcite (solid arrow) that was torn off (hollow arrow) and re-deposited within the internal sediment. Devonian reef limestone, Germany. Width of photograph is 6 cm. C: Subhorizontal fracture in fine-grained dolostone (black, top and bottom). Fibrous anhydrite with distinctive inclusion trails fills the fracture, indicating that the fracture was filled concomitantly with subvertical dilation by the crack-seal mechanism (Machel, 1985). Devonian dolostone, Alberta, Canada. Width of photograph is 7.5 cm.
Display large image of Figure 7
Figure 8. Blocky burial cements and paragenetic sequence in thin section. A: Blocky anhydrite cement in secondary vug. Solid bitumen (black) coats many of the crystals and occurs in microfractures and along cleavage planes. Some crystals contain oil in primary fluid inclusions. Devonian dolostone of Alberta, Canada. Width of photomicrograph is 2 mm. B: Coral mold in dolostone filled with calcite (c, stained dark) and coarse anhydrite (a). The anhydrite partially replaces the calcite. Solid bitumen occurs in some remnant porosity. Devonian reef rock, Alberta, Canada. Width of photomicrograph is 1 cm. C, D: Cavity with multiple diagenetic and sedimentary features. The paragenetic sequence consists of 8 parts. 1: micritization of skeletal fragment; 2: scalenohedral calcite cement in primary porosity; 3: micritic internal sediment; 4: opening of fracture; 5: internal sediment, three different sub-facies; 6: blocky calcite spar; 7: dolomite cement; 8: ferroan calcite spar. Devonian reef limestone, Germany. Width of photomicrograph is 3.5 cm.
Display large image of Figure 8
44 The most common textural manifestations of recrystallization of carbonate cements are the enlargement of crystals (Ostwald ripening) and partial elimination of primary crystal or grain boundaries (Figs. 9A, B). Cathodoluminescence images of recrystallized carbonates commonly are ‘ blotchy'. Recrystallization also results in changes in crystal structure, isotopic composition, and paleomagnetic properties (e.g., Machel, 1997).
45 For practical applications, the absence, presence and/or degree of recrystallization is/are important for genetic interpretation. Consider, for example, a dolostone. If recrystallization changes or resets the original properties of the cystals, such as texture, structure, composition, and/or paleomagnetic properties, beyond what they were in the pristine (unrecrystallized) rock, the dolostone is said to be "significantly recrystallized". The reset properties are no longer representative of the fluid and environment during dolomitization but they reflect the recrystallization event. However, some measurable properties may not be reset and they will represent the dolomitization event. If recrystallization resets only one of 10 properties (e.g., 87 Sr/86 Sr-ratios) beyond the range in the pristine rock, the dolostone is significantly recrystallized with respect to Sr-isotopes, yet insignificantly recrystallized with respect to the other nine properties. In either case, values of those properties that are identical to the pristine reference values can be used for genetic interpretations of dolomitization.
46 The concept of "significant recrystallization" is of great use in genetic interpretations. In particular, for a reliable interpretation of the chemistry of the diagenetic fluids, it is sufficient to recognize that a crystal is insignificantly recrystallized (Machel, 1997).
Replacement
47 Next to dolomite (discussed separately below), the most common replacive mineral in deep carbonate aquifers, is anhydrite. For example, extensive anhdrite replacement of dolostones, with or without concomitant anhydrite cementation, is well known from the Devonian strata of western Canada (e.g., Walls and Burrowes, 1985). Replacive anhydrite commonly is massive but may also resemble primary nodular or bedded sulfates, which is best recognized where reef rock is replaced (Fig. 9C). At depths of less than 600m (up to 1000m depending on temperature and fluid composition), gypsum forms rather than anhydrite because the gypsum-anhydrite stability boundary is crossed somewhere in this interval. Furthermore, replacive gypsum generally dewaters and recrystallizes to anhydrite, generating distinctive microtextures (Fig. 9D).
Figure 9. Common recrystallization (A, B) and replacement (C, D) textures. A, B: Recrystallized coral (c) and fibrous calcite cement (fi) (A: single-polar, B: crossed-polar photomicrograph). Note than all crystal boundaries appear ‘ diffuse' and that large crystals consist of numerous subcrystals. The dark domains at top left and right are intraparticle and interparticle primary pores, respectively, filled with micritic sediment. Devonian reef limestone, Germany; width of photomicrographs is 0.5 cm. C: Massive, white anhydrite replacing coral dolostone, a part of which is preserved at centre-right. Devonian reef dolostone, Alberta, Canada; width of photograph is 6 cm. D: Thin section photomicrograph, crossed polars, of anhydrite shown in Figure C. Large, marginally corroded porphyrotopic crystals are embedded in fine-crystalline matrix [‘ corrotopic anhydrite']. This texture is typical of gypsum recrystallized to (replaced by) anhydrite.
Display large image of Figure 9
48 Dolomite and silica (chert) are other common replacements of limestone. The resulting textures can be predicted from thermodynamic considerations to some degree. As Fletcher and Merino (2001) have shown, the induced stress by quartz growing replacively toward and within calcite is very small (Fig. 6); hence, quartz tends to form euhedral crystals in limestone. The same is true for dolomite in limestone, at least at relatively low temperatures. However, where gypsum grows in limestone, the induced stress at the grain boundaries is very large; thus, calcite tends to deform or fracture, unless there is enough porosity to accommodate the sulfate.
49 Replacement of carbonates by calcium sulfate can have a pronounced effect on porosity and permeability. Regardless of the actual quantities of anhydrite formed relative to dolomite replaced or cemented, dolostones commonly are porous, whereas anhydrite is tight. Hence, any anhydrite cement or replacement will reduce the porosity significantly. Permeability, however, is not necessarily affected to a proportional degree. Anhydrite generally has a low nucleation rate and thus a tendency to grow in a few patches of large crystal aggregates, rather than forming pervasively throughout the rock. As a result, more than about 60% of the total rock volume has to be filled or replaced by anhydrite cement before the permeability is reduced to any significant degree (Lucia et al., 2004). At lesser amounts of anhydrite in the rock, the formation fluids (water and/or petroleum) tend to flow around the large patches of anhydrite.
Epimetamorphic Fluids and Tectonic Injection
50 Diagenesis in the deepest parts of the diagenetic realm is a poorly understood phenomenon because it grades into the epimetamorphic realm. Some authors (Land, 1997; Schroyen and Muchez, 1998) advocate that material can be transferred from the crystalline basement into the overlying deep burial diagenetic setting. Prograde metamorphism and devolatilization reactions liberate water and CO2 , which are added to the sedimentary basin above. In the case of the Western Canada Sedimentary Basin, there is petrographic, isotopic, and circumstantial evidence for injection of Laramide metamorphic fluids into the Devonian carbonate aquifers in the deepest part of the basin (Machel and Cavell, 1999). The fluid fluxes appear to be low, however, as shown by the relatively small amounts of cement formed, commonly white sparry calcite (Machel et al., 2001). The effects of this type of fluid flow on reservoir properties are not yet understood.
Processes and Features Occurring and/or Forming Across Several Burial Diagenetic Zones
Fractures
51 Where fractures are restricted in lateral or horizontal extent within one of the diagenetic burial zones (Fig. 2), diagenesis within the fractures is generally similar or identical to that within the adjacent wall rocks. Where fractures cross from one diagenetic zone into another, however, relatively cold groundwaters may descend or relatively hot groundwaters may ascend fairly rapidly. Hence, the fractures in any diagenetic zone may contain hydrofrigid (and underpressured) or hydrothermal (and overpressured) fluids relative to those in the surrounding wall rocks (Machel, 1999; Machel and Lonnee, 2001). This situation raises numerous possibilities for mineral reactions, especially when the fractures transect different rock types (e.g., Pedersen and Bjørlykke, 1994; Stoute and Harris, 1995). A comprehensive discussion of these possibilities is beyond the scope of this paper. The following examples characterize the most common and perhaps most important aspects of formation water flow though fractures.
52 Rapid descent of cool meteoric waters to depths of several kilometres through deep-reaching faults/fractures is common in mountainous recharge areas. In Western Canada, for example, such hydrologic systems are common in the Rocky Mountain Front Ranges, where meteoric waters convectively descend and return to the surface in sulfurous hydrothermal springs, e.g., at Miette, Banff, and Radium. The diagenetic effects in the descending parts of these flow systems are virtually unknown, except that the waters appear to equilibrate isotopically rather fast in at least some locations (Nesbitt and Muehlenbachs, 1997). The major effect in the ascending parts of these flow systems is massive cementation within the fractures, which commonly reach centimetre and locally decimetre dimensions, and are filled with sparry calcite or dolomite, quartz, and to a minor degree with other minerals, including sulfates and fluorite (Nesbitt and Muehlenbachs, 1997).
53 Similarly, from a hydrogeological point of view, rapid convection of meteoric waters is known from intermontane rift basins. In one of the best studied examples, Tóth and Otto (1994) demonstrated that meteoric waters move preferentially through fractures from recharge areas in the mountains that fringe the Rhine Graben toward the enclosed valley, where they discharge as hydrothermal and petroliferous brines. Radiocarbon data from waters of producing wells range from 3,165 to 31,000 years, indicating that convection is very rapid. The diagenesis within the fractures has not been investigated, however.
54 Rapid ascent of hydrothermal fluids derived from shallow-metamorphic and deep-burial diagenetic settings is well known from many sedimentary basins. Perhaps the best known effect of such "hydrothermal groundwater flow" is Mississippi-Valley-Type Pb-Zn-(saddle) dolomite mineralization that may be restricted to fractures, or that may partially replace adjacent wall rocks (e.g., Anderson and Macqueen, 1982; Braithwaite and Rizzi, 1997; Gregg et al., 2001).
55 Fibrous minerals in fractures indicate a special mode of fracture opening and filling, commonly referred to as "crack-seal" (Ramsey, 1980). In this case, the pore fluids precipitate minerals as fast as the fractures are opening, which may happen in multiple episodes, such that the actual space between the facture walls never exceeded a few nanometres or micrometres (Machel, 1985). An example of fibrous anhydrite is shown in Figure 7C. Ramsey (1980), Machel (1985) and others have interpreted the fibrous crystals to be passively precipitated in veins that opened under externally applied stress. An alternative interpretation has been provided by Wiltschko and Morse (2001), who advocated that such fibrous mineral veins originate from the vein mineral(s) actively pushing the wall rock apart.
56 Fractures commonly serve as migration pathways for petroliferous fluids. In such cases, the fluids may form minerals with petroliferous fluid inclusions and/or solid bitumen in the fractures, which can be used to determine hydrocarbon migration pathways and related aspects, such as timing of migration and fluid composition (e.g., Levine et al., 1991). In deeply buried and tightly sealed reservoirs, fractures are not only used by hydrocarbons as migration pathways but they may be generated by the pressure from in-situ hydrocarbon generation, either oil or gas from kerogen, or gas from oil. Especially well documented examples of this phenomenon occur in Devonian reefs in the deepest part of the Alberta Basin, Canada, where in-situ cracking of oil to gas has led to intense hairline fracturing that appears as pervasive "shattering" of the rocks (Marquez and Mountjoy, 1996; Fig.10).
51 Where fractures are restricted in lateral or horizontal extent within one of the diagenetic burial zones (Fig. 2), diagenesis within the fractures is generally similar or identical to that within the adjacent wall rocks. Where fractures cross from one diagenetic zone into another, however, relatively cold groundwaters may descend or relatively hot groundwaters may ascend fairly rapidly. Hence, the fractures in any diagenetic zone may contain hydrofrigid (and underpressured) or hydrothermal (and overpressured) fluids relative to those in the surrounding wall rocks (Machel, 1999; Machel and Lonnee, 2001). This situation raises numerous possibilities for mineral reactions, especially when the fractures transect different rock types (e.g., Pedersen and Bjørlykke, 1994; Stoute and Harris, 1995). A comprehensive discussion of these possibilities is beyond the scope of this paper. The following examples characterize the most common and perhaps most important aspects of formation water flow though fractures.
52 Rapid descent of cool meteoric waters to depths of several kilometres through deep-reaching faults/fractures is common in mountainous recharge areas. In Western Canada, for example, such hydrologic systems are common in the Rocky Mountain Front Ranges, where meteoric waters convectively descend and return to the surface in sulfurous hydrothermal springs, e.g., at Miette, Banff, and Radium. The diagenetic effects in the descending parts of these flow systems are virtually unknown, except that the waters appear to equilibrate isotopically rather fast in at least some locations (Nesbitt and Muehlenbachs, 1997). The major effect in the ascending parts of these flow systems is massive cementation within the fractures, which commonly reach centimetre and locally decimetre dimensions, and are filled with sparry calcite or dolomite, quartz, and to a minor degree with other minerals, including sulfates and fluorite (Nesbitt and Muehlenbachs, 1997).
53 Similarly, from a hydrogeological point of view, rapid convection of meteoric waters is known from intermontane rift basins. In one of the best studied examples, Tóth and Otto (1994) demonstrated that meteoric waters move preferentially through fractures from recharge areas in the mountains that fringe the Rhine Graben toward the enclosed valley, where they discharge as hydrothermal and petroliferous brines. Radiocarbon data from waters of producing wells range from 3,165 to 31,000 years, indicating that convection is very rapid. The diagenesis within the fractures has not been investigated, however.
54 Rapid ascent of hydrothermal fluids derived from shallow-metamorphic and deep-burial diagenetic settings is well known from many sedimentary basins. Perhaps the best known effect of such "hydrothermal groundwater flow" is Mississippi-Valley-Type Pb-Zn-(saddle) dolomite mineralization that may be restricted to fractures, or that may partially replace adjacent wall rocks (e.g., Anderson and Macqueen, 1982; Braithwaite and Rizzi, 1997; Gregg et al., 2001).
55 Fibrous minerals in fractures indicate a special mode of fracture opening and filling, commonly referred to as "crack-seal" (Ramsey, 1980). In this case, the pore fluids precipitate minerals as fast as the fractures are opening, which may happen in multiple episodes, such that the actual space between the facture walls never exceeded a few nanometres or micrometres (Machel, 1985). An example of fibrous anhydrite is shown in Figure 7C. Ramsey (1980), Machel (1985) and others have interpreted the fibrous crystals to be passively precipitated in veins that opened under externally applied stress. An alternative interpretation has been provided by Wiltschko and Morse (2001), who advocated that such fibrous mineral veins originate from the vein mineral(s) actively pushing the wall rock apart.
56 Fractures commonly serve as migration pathways for petroliferous fluids. In such cases, the fluids may form minerals with petroliferous fluid inclusions and/or solid bitumen in the fractures, which can be used to determine hydrocarbon migration pathways and related aspects, such as timing of migration and fluid composition (e.g., Levine et al., 1991). In deeply buried and tightly sealed reservoirs, fractures are not only used by hydrocarbons as migration pathways but they may be generated by the pressure from in-situ hydrocarbon generation, either oil or gas from kerogen, or gas from oil. Especially well documented examples of this phenomenon occur in Devonian reefs in the deepest part of the Alberta Basin, Canada, where in-situ cracking of oil to gas has led to intense hairline fracturing that appears as pervasive "shattering" of the rocks (Marquez and Mountjoy, 1996; Fig.10).
Bacterial and Thermochemical Sulfate Reduction
57 Dissolved sulfate and hydrocarbons are thermodynamically unstable together in virtually all diagenetic environments. Hence, redox-reactions occur, whereby sulfate is reduced by hydrocarbons either bacterially (bacterial sulfate reduction = BSR) or inorganically (thermochemical sulfate reduction = TSR). Their geological and economically significant products are similar and can be formed in or across several burial zones. Based on empirical evidence, BSR and TSR occur in two mutually exclusive thermal regimes (Fig. 11): low-temperature and high-temperature diagenetic environments, respectively (Machel et al., 1995a; Machel, 2001).
58 BSR is common in diagenetic settings from zero to about 80°C. Above this temperature range, almost all sulfate-reducing microbes cease to metabolize, although they may persist in a dormant state. Those few types of hyper-thermophilic microbes that can form H2S at temperatures up to 110°C appear to be very rare and they do not normally occur and/or metabolize in geologic settings that are otherwise conducive to BSR.
59 TSR appears to be common in geologic settings with minimum temperatures in the range of 100 to 140°C, while in some settings minimum temperatures of up to 180°C are necessary. TSR does not have a sharply defined minimum temperature because the onset and rate of TSR are governed by several factors that vary from place to place. These factors include the composition of the available organic reactants, kinetic inhibitors and/or catalysts, anhydrite dissolution rates, wettability, as well as migration and diffusion rates of the major reactants toward one another (Machel, 1998).
Figure 10. Microfractures in polished core samples from deeply buried and tightly sealed carbonate reservoirs in Alberta, Canada. A: Dense network of microfractures filled with bitumen (black). cm-ruler for scale. B: Subhorizontal microfractures, bitumen filled (arrow), in coral fragment. The fractures stop at the boundary with the adjacent bladed cement (c), presumably because the latter was more ductile. Scale bar = 250 micrometres. C, D: Subvertical and subhorizontal sets of bitumen-filled microfractures. Scale bar = 250 micrometres. E : Microfractures distributed radially around nearly spherical mold (arrow) in dolomitized reef rock. In addition, multiple sets of subhorizontal microfractures extend from intercrystalline pores and dissolution vugs into the matrix and adjacent fossil fragments.
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Figure 11. Generalized relationships between oil and gas generation, temperature, thermal maturity, and bacterial and thermochemical sulfate reduction (BSR and TSR, respectively), assuming normal geothermal gradients of 25 to 30°C/km (diagram is modified from Machel et al., 1995a). Solid arrows indicate the normal thermal regimes for BSR and TSR; hollow arrows denote extreme and geologically unusual conditions. Note that the upper part of the BSR temperature range overlaps with the lower part of the liquid oil window.
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60 The most important redox-reactions involving BSR and TSR can be represented by a common set of mass and charge balance reactions (Table 1). All reactions representing inorganic processes are reversible but are shown only in that direction to which they proceed under the specified conditions. Each microbial reaction involves numerous enzyme-catalyzed steps that are omitted for clarity. Reactions 1 and 2 are specific to BSR and TSR, respectively, whereas most redox-reactions involving hydrocarbons and inorganic sulfur compounds are valid for both BSR and TSR. For a more comprehensive discussion of the geological, experimental and theoretical evidence for these reactions, see Machel (1987) and Machel et al. (1995a).
61 The main organic reactants for BSR are organic acids, methane, and other products of aerobic or fermentative biodegradation. The main organic reactants for TSR are branched and nalkanes, followed by cyclic and monoaromatic species, in the gasoline range. Sulfate is derived almost invariably from the dissolution of primary or secondary gypsum and/or anhydrite at or near the redox-reaction site(s).
62 The products of BSR and TSR are similar, but their relative amounts vary widely and are determined by a number of locally variable factors, including availability of reactants, formation water chemistry, and wettability (Machel, 1997, 2001; Machel et al., 1995a). The primary inorganic reaction products in both thermal regimes are H2S (HS - ) and HCO3 - (CO2 ). Carbonates, particularly calcite and dolomite, commonly form if alkali-earth metals are present in the formation waters. Other carbonates, i.e., ankerite, siderite, witherite, strontianite, may form if the respective metal cations are available. Iron sulfides, galena, and sphalerite form as by-products of hydrogen sulfide generation, if the respective transition or base metals are present or transported to the BSR/TSR reaction site. Elemental sulfur may accumulate as a volumetrically significant net reaction product, generally when the system runs out of reactive hydrocarbons. Water may form as a by-product and can cause a local dilution of the formation waters at or near the reaction site. There are case studies of TSR, however, where no dilution of the formation water has occurred, indicating that the amount of water released during TSR was negligible. Porosity may be generated during TSR, but most case studies show that TSR does not normally increase porosity significantly.
63 TSR is likely to take place in fairly narrow reaction zones, where the irreducible water saturation in the hydrocarbon-containing pores is low. In the Nisku Formation of Alberta, Canada, this zone is about 10 - 20 m thick (Machel et al., 1995b). However, where the irreducible water saturation is high, TSR may take place throughout the entire hydrocarbon-containing pore volume. Solid bitumen may form as a byproduct of both BSR and TSR. Finally, the net reaction may be exothermic or (more commonly) endothermic, depending on reaction stoichiometry (Simpson et al., 1996; Simpson, 1999).
64 The mere presence of any of the above reaction products and by-products does not permit a distinction between BSR and TSR. However, a number of petrographic relationships and geochemical criteria can be used to discriminate between these two processes (Machel et al., 1995a). Specifically, most solid products of BSR and TSR, although similar in gross composition, can be distinguished from one another petrographically. Most BSR products form early, whereas most TSR products form late, in the paragenesis, and have distinctive crystal sizes, shapes, and/or reflectivity. However, there also are cases where BSR products formed relatively late diagenetically, such as in uplifted reservoirs after hydrocarbon migration. Gas chromatography, δ13 C-, δ34 S-analyses, and/or a combination thereof, offer the best distinguishing geochemical criteria (Machel et al., 1995a).
Table 1. Reaction scheme for bacterial and thermochemical sulfate reduction (BSR and TSR, respectively). Reactions 1 and 2 appear to be pre-requisites for BSR and TST, respectively. Reactions 3 to 5 exemplify all important redox steps for both BSR and TSR. The net reaction represents reactions 3, 4, and 5 if all elemental sulfur generated in reaction 4 is used up in reaction 5. See text for further explanation.
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Dolomitization
65 One of the most important effects of groundwater flow on carbonate aquifers and potential reservoir rocks is pervasive replacive dolomitization, which commonly but not necessarily results in a concomitant increase in porosity and permeability. Mass balance calculations indicate that large fluid fluxes are necessary for extensive, pervasive dolomitization, because of the generally low Mg-content of natural waters. From 6,500 to 10,000 m3 of brackish to fresh groundwaters (the former containing about 10% seawater) would be required to dolomitize one cubic metre of limestone with an initial porosity of 40%, or 650 m3 of seawater, the most common Mg-rich water in nature, would be required (Land, 1985). Porosity generally increases during dolomitization because generally about two moles of calcite are replaced by one mole of dolomite, with a concomitant decrease in the molar volume by about 13%. Other reaction stoichiometries, however, may result in little porosity change or in porosity loss during dolomitization (e.g., Machel and Mountjoy, 1986). Also, continued flux of fluids supersaturated with respect to dolomite may lead to cementation of pore spaces with dolomite after complete matrix replacement, a process termed "overdolomitization "(Lucia 2000). In extreme cases, the resulting dolostones are essentially non-porous and impermeable.
66 Massive dolostones with enhanced porosity and permeability relative to their limestone precursors are common all over the world. Popular dolomitization models (Fig. 12) typically depict limestones embedded in some type of local, intermediate, or regional groundwater flow system that is invoked to pump the necessary amounts of Mg through the rocks (various articles in Purser et al., 1994; Mountjoy et al., 1997; Machel, 2004). Thereby, the distribution, texture, and geochemical composition of the dolostones are fitted to perceived or possible models, in an attempt to obtain a viable genetic interpretation. Such models span all diagenetic settings from near-surface to the metamorphic realm, as well as almost any type of hydrologic flow system and geochemical composition.
Microbial Action
67 Most microbes live in near-surface or shallow subsurface diagenetic settings where temperatures and pressures are relatively low and nutrients are abundant. Temperature and pressure increase with increasing depth and nutrients become scarce, which leads to a general decrease in the rates of metabolic activity and eventually to death of all microbes. The various types of microbial activity and products in petroliferous subsurface settings have recently been summarized by Machel and Foght (2000), in an attempt to place absolute depth limits on the geologically significant groups of microbes.
Figure 12. Diagrams of several groundwater flow systems (left) and predicted dolomitization patterns (right). Examples are of incomplete dolomitization of carbonate platforms or reefs. Arrows denote flow directions; dashed lines show isotherms. Predicted dolomitization patterns are shaded. Models A-D1 and D4 are km-scale; model D2 and D3 are basin-scale. Reproduced from Machel (2004).
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68 Four groups of microbes are known to be geologically significant in petroliferous subsurface settings (Machel and Foght, 2000), namely aerobic respiratory bacteria, and three anaerobic groups that commonly live in consortia (symbiotic communities): fermentative, sulfate-reducing, and methanogenic bacteria. These microbes form a number of economically important products and by-products in subsurface settings. The aerobic microbes, generally called biodegrading bacteria, form mainly napthenic crude oils and tar in the form of tar sand deposits (Tables 2 and 3). The role of fermentative microbes is mainly in the partial breakdown of organic molecules that then serve as nutrients for the sulfate reducers and the methanogens. Sulfate-reducing microbes form mainly H2 S, metal sulfides, and elemental sulfur, wheras methanogenic bacteria form mainly methane. In all cases, carbonate cements with distinctive isotopic compositions may be formed as by-products. In addition, nanobacteria may be important in clay mineral diagenesis in buried sandstones. Various types of microbes from the above groups can be used for microbially enhanced recovery of oil. Ultramicrobacteria constitute a special class, as they are injected in a dormant state and then resuscitated in situ to form biobarriers.
69 In the subsurface, temperature appears to be the principal factor limiting microbial metabolism (and life), followed by the availability of suitable nutrients. All four groups of bacteria generally become inactive by a subsurface depth of about 2000 m, except for rare cases where aerobic biodegradation or sulfate reduction can occur as deep as about 3000 m (Machel and Foght, 2000). Sulfate-reducing bacteria appear to be able to tolerate the highest temperatures, up to at least 110°C. However, they normally are subject to the same depth limitations as the aerobic biodegraders (Fig.13), whose "waste" products they may use as nutrients. Similarly, most methanogenic bacteria appear to become dormant or are dead at depths greater than about 2000 m (Fig. 14). This, however, does not preclude that sulfate-reducing and/or methanogenic microbes may metabolize in rare and unusual cases at greater depths. Furthermore, the lower limit of the biosphere probably is marked by other types of bacteria or archeae at much greater depths.
Porosity and Permeability in Limestone-Dolostone Sequences
70 Porosity and permeability development transgresses all diagenetic zones and is a direct result rather than a process of diagenesis. For petroleum engineering, this development is the most important aspect, especially when comparing limestone with dolostone sequences.
71 It has long been claimed that most dolostones are more porous and more permeable than limestones (Van Tuyl, 1914; Blatt et al., 1972), a circumstance of obvious importance for the petroleum industry. A related aspect is that dolostones generally form aquifers and preferential migration pathways for hydrocarbons, or both. However, Schmoker and Halley (1982) and Halley and Schmoker (1983) demonstrated that many dolostones have porosities equal to or less than those of adjacent limestones, based upon porosity/depth profiles of Cenozoic carbonates in southern Florida, which have not been buried too deeply (less than 1 km). Budd (2001) showed that the same is true for the permeability in these particular rocks, i.e., many dolostones have permeabilities equal to or less than those of the adjacent limestones. On a larger scale, Schmoker et al. (1985) compared thousands of limestones and dolostones from across the U.S.A. and found that dolostone reservoirs commonly have lower matrix porosities and permeabilities, yet higher fracture porosities and permeabilities, than limestones. Amthor et al. (1994), however, in a study of 31 wells from Devonian reservoirs in Alberta that span a depth range of several thousand metres, found that there is a distinctive dependence on depth. If considered irrespective of depth, limestones and dolomitic limestones are more porous than dolostones, whereas at burial depths of greater than 2000 m dolostones are significantly more porous and permeable than limestones. There also are notable examples of very young, near-surface dolostones that are tight and apparently devoid of porosity, as in the Plio-Pleistocene carbonates of Bonaire (Lucia and Major, 1994).
Table 2. Aerobic biodegradation effects on gross properties of petroleum (modified from Connan, 1984).
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Table 3. Changes in molecular properties with increasing level of aerobic biodegradation (compiled from Volkman et al., 1983; Connan, 1984; Hunt, 1996).
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72 The major processes involved in porosity-permeability (poroperm) generation are summarized in Figure 3. Six specific processes are especially important in the case of limestone-dolostone sequences: (a) mole-per-mole replacement; (b) dissolution of unreplaced calcite (solution undersaturated for calcite after all Mg in excess of dolomite saturation is exhausted); (c) dissolution of dolomite (without externally controlled acidification); (d) acidification of the pore waters (via decarboxylation, clay mineral diagenesis, etc.); (e) fluid mixing (Mischungskorrosion); and, (f) thermochemical sulfate reduction, which may generate porosity under certain circumstances (Machel, 2001, 2004). The wide scatter and lack of systematic relationships between the porosity of limestones and dolostones in Florida and Alberta probably reflects locally and regionally heterogeneous interplays among the various processes that generate, preserve, or destroy porosity (Fig. 3).
73 Dolomitization almost invariably involves the reorganization of permeability pathways. Commonly permeability increases along with porosity, and vice versa. This is documented through studies such as the one on the Late Devonian Grosmont Formation in eastern Alberta, which hosts a giant heavy-oil reservoir (Luo et al., 1994; Luo and Machel, 1995; Machel and Huebscher, 2000). A comparison of porosity and permeability data from 237 core plugs reveals an overall positive correlation, despite considerable scatter. This correlation is also expressed in the displacement pressures from mercury injection capillary measurements, which permit the identification of four major and two minor dolomite reservoir rock types. Using a similar approach (thin section and SEM petrography combined with helium porosimetry and mercury injection capillary measurements), Woody et al. (1996) also documented positive and statistically significant correlations between porosity and permeability for planar dolomites in the Cambrian-Ordovician Bonneterre Formation of Missouri, U.S.A., which is host to one of the world's largest MVT-sulfide deposits.
Figure 13. The difference in sulfur isotope composition between sulfate dissolved in formation waters and hydrogen sulfide versus depth from three sedimentary basins (after Krouse, 1977). High isotope values at depths less than about 2000 m indicate in situ BSR, the effect of which diminishes with increasing depth. At depths below about 2200 m, BSR appears to be volumetrically insignificant and all H2 S is thermochemical.
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Figure 14. Change in δ13 C and the percentages of CH4 (C1 ) and C2+ in head space gas from well 33/6-1 in the North Sea (after Schoell, 1984). The gases generated above about 2000 m are dry and biogenic, with very low methane δ13 C values of about -70 ‰ PDB. Gases generated below about 2000 m are wet and thermogenic, with much higher methane δ13 C values of about -40 ‰ PDB. The transition shown by the δ13 C values between about 1000 to 2000 m indicates upward escape of thermogenic gas and mixing with the biogenic gas.
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74 Other authors have disputed that there is a systematic correlation between porosity and permeability in dolostones, or that these two petrophysical parameters are enhanced in dolostones relative to limestones. Halley and Schmoker (1983), in the absence of reliable or sufficient permeability data, attempted to assess the permeability of carbonate rocks from porosity data. They found that carbonate aquifers and carbonate aquicludes cannot be distinguished on the basis of porosity. Lucia (2002, 2004) claimed that "....there is no relationship between porosity and permeability in dolostones...... and dolomite crystal sizeand the precursor fabric are key elements in predicting permeability", and "Dolomitization of grain-dominated limestones usually does not change porosity-permeability relationships. Instead, the precursor fabric controls pore-size distribution." While this may be so in some, perhaps many cases, the Grosmont and the Bonneterre examples clearly show that there is a relationship between porosity and permeability in at least some major and economically important dolostone sequences.
THE "6 - STEP PROCESS"
75 This writer has found that many investigations of burial diagenesis, whether of carbonates or of clastics, proceed in six steps that roughly correspond to those in the top half of Figure 15. However, such studies should proceed in the "6 -Step Process" shown in the bottom half of Figure 15, with the last step being optional.
76 Step 1: Facies analysis (outcrop, core, thin section). Facies analysis is necessary because depositional factors and processes, such as bathymetry and water agitation, determine the primary poroperm distribution. These, in turn, control the extent to which diagenetic fluids later permeate the rocks, creating secondary porosity, cements, replacements, etc. An example of a facies analysis is shown in Figure 16. Facies analysis should be preceded by, or done in combination with, characterization of stratigraphy and structure for an overall 3D context, if possible.
77 A commonly neglected aspect is the "primary aquastratigraphy", which is herein defined as the syn-sedimentary pore fluid stratification that can be correlated with, or deduced from, the facies analysis. The primary aquastratigraphy is extremely important for diagenetic investigations. For example, the sedimentary sequence depicted in Figure 17, would have contained, at the time of deposition, normal seawater in the lower part, meteoric water in the middle and evaporitic brine at the top. The low-density meteoric water would not be able to displace the underlying seawater, unless an external hydrologic force would overcome the density difference. However, the evaporitic brine would move downward and displace both the meteoric water and the seawater in the sedimentary sequence, probably leading to an evaporitic diagenetic overprint very soon after deposition, including changes in the isotopic and trace element compositions. Such phenomena would remain undetected and/or misinterpreted without a proper facies analysis.
78 Step 2: Establish the paragenetic sequence of diagenetic events (Fig. 18) on the basis of petrography (outcrop, core, thin section, including UV and CL microscopy). This may involve the identification of shallow and deep burial cements using petrographic criteria, cement sequence (cement stratigraphy), intervening episodes of deposition of internal sediment(s), fracturing, dissolution, and recrystallization. Under favorable circumstances, broad depth limits can be assigned, such as less than 10 m for sea floor diagenetic processes, less than 300 m for processes predating stylolitization, etc. (as discussed in Machel, 1999). Investigation of cements and porosity in core and thin section can be combined with extant poroperm data from plugs and full diameter core, in order to map out porosity and permeability on a reservoir scale.
79 Step 3: Obtain various physical (P/T, crystal structure) and geochemical (isotopes, trace elements) and/or paleomagnetic data for selected diagenetic phases of interest, such as replacive dolomite(s), sparry calcite cements, etc. Most rock geochemical methods involve microdrilling (in the old days wholesale milling) to obtain powder samples for subsequent geochemical analysis. Such geochemical work is commonly referred to as "bulk analysis". Every attempt should be made to extract individual diagenetic phases, which is possible by these methods only with relatively large crystals. To achieve higher resolution and/or analyze individual growth zones, spot analyses by microbeam techniques may be carried out. With modern technology, spot sizes are commonly smaller (a few tens of micrometres) than the width of typical cement growth zones. However, this type of work requires expensive and generally unobtainable instrumentation. A further problem is that some of the desired analyses are notoriously difficult or impossible to obtain with sufficient accuracy using microbeam techniques, such as the light isotope ratios (oxygen, carbon), and detection limits for trace elements usually are much higher than by bulk analytical techniques. Hence, a compromise has to be struck. Some types of analysis are entirely non-destructive, such as cathodoluminescence imagery and spectroscopy, or microthermometry of fluid inclusions. The available data are then depicted in a combination of diagrams (an example is shown in Fig. 19), and are interpreted in terms of fluid composition, temperature, etc. Where formation fluids can be obtained from well heads, an attempt can be made to relate the present formation water chemistry to that inferred from the rock geochemistry. Data from Step 3 are then integrated into the paragenetic sequence (Fig.18) and, where possible, absolute timing is assessed using radiometric or paleomagnetic data.
Figure 15. The "6-Step Process", normal and recommended phases of a project.
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Figure 16. Facies model for Middle to Late Devonian reef carbonates from Machel and Hunter (1994). Part A indicates water energy by noting rounding and sorting. Part B refers to the texture. Part C records the amount of micrite in the sample. Part D lists the amount, size, and type of porosity. Part E tabulates the widely distributed fossils in each particular zone. These fossils have their distributional maxima in the zone(s) noted. Part F lists fossils which are usually found only in the backreef, forereef, or reef core, respectively.
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Figure 17. Facies analysis and the concept of "primary aquastratigraphy". See text for further explanation.
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80 Step 4: Establish burial curves, as deduced from stratigraphic, compaction, and/or thermal maturation data (Fig.20), and corresponding interpretation (in some cases educated speculation) of the paleohydrology (Fig. 21).
81 Step 5: Integrate with relevant extant data, especially standard petrophysical investigations (Lucia, 2000), if possible.
82 Step 6 (optional): Modeling, either forward or backward, of (a) facies (= primary porosity) parameters, such as from sequence stratigraphy (e.g., Tinker, 1996), (b) burial and thermal history (e.g., various studies reviewed in Hunt, 1996), (c) chemistry (e.g., Meshri and Ortoleva, 1991), as well as (d) present and past hydrology (England and Fleet, 1991; Rostron et al., 1997; Gvirtzman and Stanislavsky, 2000). In some modern studies, two or more types of modeling are undertaken in combination. However, as powerful as these types of modeling may be in certain cases, they are considered optional in the present context. Modeling is not necessary for most practical questions that a petroleum geologist is concerned with in a study of diagenesis.
83 Finally, it should be noted that the term "model" is used here in its true definition. It is necessary to emphasize this point because the term "model" is widely misused and generally subsituted for the term "interpretation". A model is not the same as an interpretation. Rather, a model is a complex concept that is based on a set of criteria, one of which is an interpretation: "a working hypothesis or precise simulation, by means of description, statistical data, or analogy, of a phenomenon or process that cannot be observed directly or that is difficult to observe directly. Models can be derived by various methods, e.g., by computer, from stereoscopic photographs, or from scaled experiments " (AGI, 1999). Walker (1992), using stratigraphic models as an example, elegantly summarized the general criteria of a model, which must act as: (1) a norm for purpose of comparison; (2) a framework and guide for future observations; (3) a predictor to new geological situations; and, (4) an integral basis for interpretation of the system it represents. Many studies have published so-called models that do not fulfill these criteria but are interpretations. Hence, Step 6 should not be mistaken for an interpretation of data.
Figure 18. Typical paragenetic sequence for Upper Devonian (D3) Leduc reefs in the central to southern parts of the Rimbey-Meadowbrook reef trend, Alberta, Canada. Based on Amthor et al. (1993), Machel et al. (1994), and Mountjoy et al. (1999).
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CONCLUSIONS
84 Porosity and permeability generally decrease with depth, but many sedimentary rocks, especially carbonates, have highly variable poroperm values that may be much higher or lower than the average. The various processes of porosity generation, preservation, and reduction "compete" with one another, and the present porosity and permeability characteristics represent the net result of all past processes. Considering the immense range of possibilities, generalized predictions of poroperm characteristics are risky, and each (carbonate) aquifer or reservoir unit should be investigated on an individual basis.
85 The methodology outlined in this article can be of great value in hydrocarbon exploration and development. Regarding the latter, the main value of diagenetic work is a better characterization of the pore and pore throat network that can be used to map or model a reservoir and its internal heterogeneities. This is especially useful in combination with petrophysical data, such as the behaviour under mercury injection. Regarding exploration, a characterization of diagenesis may help in predicting where, within a certain play type, the pools with the best porosity and permeability are located. This aspect arises out of an interpretation of paleofluid flow and the past fluid chemistry. Furthermore, many of the methods and the rationale discussed in this article can also be applied in surface geochemical exploration, which is based on leaking hydrocarbons creating distinctive diagenetic aureoles that are direct indicators for hydrocarbon pools at depth (e.g., Barker et al., 1991; Burton et al., 1993; Al-Shaieb et al., 1994; Machel, 1995; Tedesco, 1995; Schumacher and Abrams, 1996).
Figure 19. δ18 O/δ13 C-plot of Obed calcites and dolomites (see insert), compositional ranges of Late Devonian seawater calcites (SWC: brachiopods, marine cements), replacive matrix dolomites (MD) from Devonian carbonates in the Western Canada Sedimentary Basin, and calculated equilibrium values for Late Devonian seawater dolomites (SWD = dolomites formed in isotopic equilibrium from normal seawater at near-surface temperatures of 25°C). In combination with the petrographic data, this type of plot suggests that the matrix dolomites probably formed from chemically modified seawater at intermediate burial depths, and that the late calcites formed at much greater depths from hotter fluids that were charged with organic carbon from TSR. From Machel et al. (1996).
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Figure 20. Burial history diagram for the Upper Devonian Rimbey-Meadowbrook reef trend, Alberta, Canada, with an assumed geothermal gradient of 30°C/km. The two burial curves represent the shallow, northeast Leduc reef/pool and the deep, southwest Strachan reef/pool of the reef trend. Numbers 1 - 5 denote diagenetic stages. Especially noteworthy are the depth and time intervals of replacement dolomitization, oil migration, and thermochemical sulfate reduction (TSR). The Leduc reef was never buried deeply enough for TSR.
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Figure 21. Schematic representation of present-day formation fluid flow (hollow arrows) and inferred Late Cretaceous to Eocene (Laramide) tectonically-induced fluid flow (solid, black arrows) in Alberta, Canada. L.D.B. is the limit of the disturbed belt of the Canadian Rocky Moutains. Circles with X indicate present-day flow subperpendicular to the plane of view. Present flow in the upper, Cenozoic and Mesozoic parts of the basin is essentially meteoric and topography-driven. From Machel et al., (2001).
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ACKNOWLEDGEMENTS
The research leading up to the synthesis presented in this paper was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC). The constructive reviews by Ishan Al-Aasm, Dana S. Ulmer-Scholle and one anonymous reviewer are much appreciated.
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Oil-Degrading Bacteria on the Sea Bed | Tomorrow Today
アップロード日: 2010/06/22
The oil spill disaster in the Gulf of Mexico has given researcher Antje Boetius a unique opportunity: the microbiologist from Bremen is studying a special kind of oil-eating bacteria that live on the sea bed and consume the crude oil that lands there.Boetius is trying to find out how these bacteria break down the oil - and whether she can increase their appetite. She hopes to use her research to clean bodies of water contaminated by man-made spills.
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Cleaning Oil Spills by Promoting Biodegradation
アップロード日: 2010/06/20
武田邦彦教授 ガリレオ放談 第61回 日本が産油国になる日
公開日: 2013/06/21
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Cleaning Oil Spills by Promoting Biodegradation
アップロード日: 2010/06/20
OTI - Oil Treatment International
This is from their website http://oti.ag :
"SOT 11 and LOT 11 are single application products, which promote rapid natural biodegradation. This means: "Apply and walk away!" Combined with the fact that there no longer is any need for expensive disposal procedures and/or additional remediation associated with the application and handling of typical chemical products, the total cost of any oil spill cleanup is significantly reduced.
The cleaning of animals contaminated with oil, the cleaning of harbor walls and the cleaning of tanks are also single applications. To safely and effectively dispose of the resulting washings the application of SOT 11 is required.
OTI's products are long lasting when stored in a suitable environment. The advantage of this is that you do not need to replace the product as often!
Because OTI's products are entirely made of natural components there are some significant benefits: Neither OTI's products nor the resulting substances from biodegradation are toxic. Therefore there is no danger to fauna or flora at any time! There also is no risk since the neutralized oil is non-toxic, too.
OTI's products are the first products offered worldwide based on true biological degradation, the competitor's offerings are chemical, hazardous and more expensive.
A number of tests have been made with positive results. The tests of independent laboratories in various countries showed results that proved to be even better than the results of our own lab. All tests proved that neither OTI's products nor the resultant products of biodegradation are toxic. All tests also revealed high bioremediation effectiveness of our products.
All products are available. Although OTI consistently invests in R&D, the products presented on this website are available and work as designed.
End-users come from a widespread industries. In particular, oil spill fighting companies and organizations, and companies specializing in the cleaning of soils and disposal of oil."
=========================================================
This is from their website http://oti.ag :
"SOT 11 and LOT 11 are single application products, which promote rapid natural biodegradation. This means: "Apply and walk away!" Combined with the fact that there no longer is any need for expensive disposal procedures and/or additional remediation associated with the application and handling of typical chemical products, the total cost of any oil spill cleanup is significantly reduced.
The cleaning of animals contaminated with oil, the cleaning of harbor walls and the cleaning of tanks are also single applications. To safely and effectively dispose of the resulting washings the application of SOT 11 is required.
OTI's products are long lasting when stored in a suitable environment. The advantage of this is that you do not need to replace the product as often!
Because OTI's products are entirely made of natural components there are some significant benefits: Neither OTI's products nor the resulting substances from biodegradation are toxic. Therefore there is no danger to fauna or flora at any time! There also is no risk since the neutralized oil is non-toxic, too.
OTI's products are the first products offered worldwide based on true biological degradation, the competitor's offerings are chemical, hazardous and more expensive.
A number of tests have been made with positive results. The tests of independent laboratories in various countries showed results that proved to be even better than the results of our own lab. All tests proved that neither OTI's products nor the resultant products of biodegradation are toxic. All tests also revealed high bioremediation effectiveness of our products.
All products are available. Although OTI consistently invests in R&D, the products presented on this website are available and work as designed.
End-users come from a widespread industries. In particular, oil spill fighting companies and organizations, and companies specializing in the cleaning of soils and disposal of oil."
=========================================================
武田邦彦教授 ガリレオ放談 第61回 日本が産油国になる日
公開日: 2013/06/21
『「正しい」とは何か？ 武田教授の眠れない講義』（小学館／1,365円）、『２０１５年放射能クライシス』
http://bp.shogakukan.co.jp/takeda/ 「ガリレオ放談 －日本を斬る－」第61回「日本が産油国になる日」
http://bp.shogakukan.co.jp/takeda/ 「ガリレオ放談 －日本を斬る－」第61回「日本が産油国になる日」
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