Anaerobic hydrocarbon biodegradation in deep subsurface oil reservoirs

Biodegradation of crude oil in subsurface petroleum reservoirs is an important alteration process with major economic consequences. Aerobic degradation of petroleum hydrocarbons at the surface is well documented and it has long been thought that the flow of oxygen- and nutrient-bearing meteoric waters into reservoirs was necessary for in-reservoir petroleum biodegradation. The occurrence of biodegraded oils in reservoirs where aerobic conditions are unlikely, together with the identification of several anaerobic microorganisms in oil fields and the discovery of anaerobic hydrocarbon biodegradation mechanisms, suggests that anaerobic degradation processes could also be responsible. The extent of anaerobic hydrocarbon degradation processes in the world's deep petroleum reservoirs, however, remains strongly contested. Moreover, no organism has yet been isolated that has been shown to degrade hydrocarbons under the conditions found in deep petroleum reservoirs. Here we report the isolation of metabolites indicative of anaerobic hydrocarbon degradation from a large fraction of 77 degraded oil samples from both marine and lacustrine sources from around the world, including the volumetrically important Canadian tar sands. Our results therefore suggest that anaerobic hydrocarbon degradation is a common process in biodegraded subsurface oil reservoirs.     

Biological activity in the deep subsurface and the origin of heavy oil

At temperatures up to about 80 degrees C, petroleum in subsurface reservoirs is often biologically degraded, over geological timescales, by microorganisms that destroy hydrocarbons and other components to produce altered, denser 'heavy oils'. This temperature threshold for hydrocarbon biodegradation might represent the maximum temperature boundary for life in the deep nutrient-depleted Earth. Most of the world's oil was biodegraded under anaerobic conditions, with methane, a valuable commodity, often being a major by-product, which suggests alternative approaches to recovering the world's vast heavy oil resource that otherwise will remain largely unproduced.     

用于提高油田采收率的聚合物降解与防护

聚合物驱油是目前工业化应用程度最高的提高采收率三次采油方法，注入溶液的性能指标直接影响聚合物的增油效果，聚合物溶液的降解和防护已引起石油科技工作者的广泛关注。通过大量的室内实验和现场试验对聚合物驱油可能引起的机械降解、化学降解和生物降解进行了详细分析，对如何做好聚合物溶液降解的防护提出了可操作性的措施，在胜利油田应用后取得了预期的聚合物粘度保护效果，这对我国高含水油田聚合物驱油的广泛推广应用具有重要的现实意义。     

Biodegradation of oil in uplifted basins prevented by deep-burial sterilization.

Biodegradation of crude oil by bacterial activity--which has occurred in the majority of the Earth's oil reserves--is known to reduce greatly the quality of petroleum in reservoirs. For economically successful prospecting for oil, it is therefore important to understand the processes and conditions in geological formations that lead to oil biodegradation. Although recent studies speculate that bacterial activity can potentially occur up to temperatures as high as 150 degrees C (refs 3, 4), it is generally accepted that effective petroleum biodegradation over geological timescales generally occurs in reservoirs with temperatures below 80 degrees C (ref. 2). This appears, however, to be at odds with the observation that non-degraded oils can still be found in reservoirs below this temperature. Here we compile data regarding the extent of oil biodegradation in several oil reservoirs, and find that the extensive occurrence of non-biodegraded oil in shallow, cool basins is restricted to those that have been uplifted from deeper, hotter regions of the Earth. We suggest that these petroleum reservoirs were sterilized by heating to a temperature around 80-90 degrees C during deep burial, inactivating hydrocarbon-degrading organisms that occur in the deep biosphere. Even when such reservoirs are subsequently uplifted to much cooler regions and filled with oil, degradation does not occur, implying that the sterilized sediments are not recolonized by hydrocarbon-degrading bacteria.     

Constraints on the origins of hydrocarbon gas from compositions of gases at their site of origin

It is widely accepted that natural gas is formed from thermal decomposition of both oil in reservoirs and, to a lesser extent, the organic matter in shales from which the oil was derived. But laboratory pyrolysis experiments on shales do not reproduce the methane-rich composition typical of most gas reservoirs, leading to suggestions that other mechanisms, such as transition-metal catalysis, may be important. The discrepancy might, however, instead arise because gas (and oil) deposits have migrated from their source rocks, so that the reservoir composition might not be representative of the composition in the source rocks where the hydrocarbons were generated. To address this question, we have analysed gas samples coproduced with oils directly from a source rock (the Bakken shales, North Dakota, USA) where the local geology has prevented significant hydrocarbon migration. The methane contents of these Bakken-shale gases are much lower than that of conventional gas reservoirs, but are consistent with that from pyrolysis experiments on these shales. Thus, because these Bakken gases form with (rather than from) oils, we argue that compositional differences between gases from source rocks and conventional gas deposits result from fractionation processes occurring after hydrocarbon expulsion from the source rock.     

东营凹陷博兴地区烃源岩和油源特征

东营凹陷博兴地区沙河街组第四段上部和第三段中下部发育两套烃源岩 ,其有机地球化学特征 ,尤其是反映沉积环境的生物标志化合物特征有明显的差异。目前已发现的石油大致分为两大类 :高青、博兴油田的原油主要属于源自沙四段烃源岩的“沙四型”原油 ;小营、乔庄、梁家楼、大芦湖油田的原油主要为源自沙三段烃源岩的“沙三型”原油。金家、正理庄、纯化油田的原油混源特征明显。从纵向上看 ,沙三、沙四段中的油气主要来自本层系 ,其他层系的原油主要为混源型原油。     

高邮凹陷原油轻烃地球化学特征及群组划分

 高邮凹陷是苏北盆地油气潜力最大的凹陷,对该凹陷马家嘴、黄珏、富民、永安等9大油田原油样品的C₆~C₇轻烃特征、Mango轻烃参数及轻烃对比、蚀变星图和成熟度参数展开系统对比研究。C₆~C₇轻烃中富含正己烷,苯相对含量低,正庚烷、甲基环己烷和二甲基环戊烷的相对含量相差不大,显示高邮凹陷原油母质类型为腐泥-腐殖型。Mango轻烃参数K₁平均值为0.97,表明高邮凹陷原油具有相似的沉积环境;上含油气系统的K₂较大,平均值为0.31,表明陆源输入较大;中含油气系统的K₂较小,平均值为0.22,表明水源输入较大,下含油气系统介于两者之间,K₂平均值为0.27。由轻烃星图对比、庚烷值和异庚烷指数显示,上含油气系统的成熟度高,保存条件好;中含油气系统原油成熟度低,受次生演化作用明显;下含油气系统原油处于成熟阶段。     

海洋石油烃降解菌的降解性能与固定化研究

对2株海洋石油烃降解菌(HD-1和HD-2)进行了研究;采用气相色谱法分析了这2株菌对正构烷烃组分的降解情况。结果表明HD-1菌株对正构烷烃的降解性能优于HD-2菌株。碳链的长度对降解率有显著影响。C11能分别被HD-1和HD-2降解90.9%和73.8%,但C25却只能被降解73.3%和27.7%。采用麦饭石、孔质砂和稻壳碳固定混合菌液后,对培养液中柴油的去除率都明显高于未固定化的菌液的去除率,其中麦饭石固定化菌的去除率最高,达到98%。     

厌氧微生物对新疆六中区稠油的降解特性

厌氧微生物作为油藏中微生物的重要组成部分,受到人们越来越多的关注,但是关于对原油的降解效果和降解机制的研究报道较少.对发酵菌富集培养物和产甲烷菌富集培养物作用前后的原油进行色质联用分析,结果表明:产甲烷菌富集培养物作用后的原油,其原油族组成变化明显,饱和烃和胶质相对含量降低,而芳香烃和沥青质相对含量上升,其中正构烷烃的含量有所增加,尤其是大于C22的正构烷烃的含量增加明显,藿烷及其同系物的含量也都有所上升.而发酵菌富集培养物作用后,饱和烃、芳烃以及胶质含量都略有上升,变化最明显的沥青质作用后下降了2%,发酵菌富集培养物降解了原油中的杂环芳烃二苯并噻吩和二苯并呋喃.同时两种富集培养物对二环芳烃的降解作用明显.产甲烷菌富集培养物和发酵菌富集培养物作用后,新疆六中区原油中短链正构烷烃含量相对增加,而长链正构烷烃含量则相对减少,∑nC21-/∑nC22+值由作用前1.033分别下降到1.023和1.015,Pr/Ph的值基本都保持在0.945左右,但是Pr/nC17和Ph/nC18都有所增大.总的来说,产甲烷菌富集培养物对原油的降解作用更明显,两种不同厌氧微生物的富集培养物对原油的作用表现出了一定的选择性.     

白音查干凹陷稠油特征及其成因

通过对白音查干凹陷稠油物性及地化特征研究,认为该凹陷稠油宏观上具有高密度、高粘度、高凝固点、低饱和烃含量,饱和烃与芳烃比值小的特征;微观上烷烃色谱及生物标志物特征提供了稠油为两期混合油,成熟度属低～较成熟油的信息．利用同位素技术恢复了达－６井稠油密度,并根据生物标志物及物性特征将该凹陷稠油划分为三级降解油,结合油气藏分布规律及地化特征认为生物降解是造成该凹陷原油稠变的主要原因     

烃类混合物及油气藏流体的粘度计算模型

根据ｖａｎｄｅｒＷａａｌｓ单流体混合规则,将基于两参数ＰｅｎｇＲｏｂｉｎｓｏｎ状态方程的流体粘度计算模型应用于烃类混合物及油气藏流体粘度的计算。对３种二元烃类混合物（甲烷丙烷、甲烷正丁烷和甲烷正癸烷）的粘度进行了计算,２４３９个数据点的平均相对误差为１６．７２％．计算了９种天然气及１７种油藏原油的粘度,其平均相对误差分别为９．８０％和１７．２９％．这种模型优于现有的油气藏流体粘度模型。     

西非北加蓬次盆G区块UPC段油气成藏模式及主控因素

 加蓬盆地作为西非被动大陆边缘重要的含油气沉积盆地,是目前油气勘探的热点地区,而G区块是中国在北加蓬次盆地的重要投资勘探开发区块。对该区块地层和沉积特征,以及烃源岩、储层、盖层、输导体系等油气成藏条件的分析表明,Ｇ区块石油地质条件优越,发育有优质烃源岩,而U.P.C.段作为G区块的主力产油层,储层物性很好,且该区块储盖组合配置关系良好。G区块油藏多为受构造控制的断背斜、断块油藏,油气主要富集在构造高点。研究表明,Ｇ区块油气成藏模式为“深源充注,断层盐边砂体输导,构造成藏”,油气成藏的主控因素为与盐运动相关的构造圈闭。     

渤海湾盆地渤中凹陷深埋古潜山天然气成藏主控因素探讨

渤中凹陷钻探的两口科学探索井均在古生界潜山发现天然气流,其中科A2井经测试获日产天然气40.2×10~4m~3,揭示了渤海海域目前埋深最大、温度最高的古潜山天然气藏。根据渤中凹陷渤中21~22古潜山油气成藏条件和实际地质、测井和地震资料的综合解释,对研究区天然气成藏控制要素进行研究。结果表明:古潜山圈闭面积大,且具有完整背斜形态;深层沙四段—东三段发育大量优质高成熟烃源岩,油气源充足;古潜山储集空间为溶蚀孔洞和裂缝,储层物性较好;成藏要素匹配关系好,天然气具有明显的晚期持续充注成藏的特点。该古潜山气藏的发现,不仅是渤中凹陷深埋古潜山天然气勘探的重大突破,也是深埋古潜山油气成藏地质条件认识和勘探工程技术进步的重大成果,能够推动渤海海域乃至整个渤海湾盆地凹中深埋古潜山的油气勘探工作。     

石油污染地表土壤的微生物降解特征

在石油的生产和储运等过程中会造成土壤被石油污染的问题,进而引起生态环境损害.本文利用热蒸发烃分析仪(GHM)对石油污染土壤进行定性定量分析,进行了油污土壤的微生物降解研究.分析结果表明:油井附近的油污土壤中存在着嗜油微生物,它们对落地石油具有较明显的降解作用;抽油生产史长的油井周围土壤中存在自然驯化出的更多嗜油微生物,其近井土壤中污油的降解速度快;随着微生物降解作用的不断进行,样品中污油的相对降解速度逐渐加快,相对降解率逐渐增加,污油样品中气态组分含量随降解时间延长而增加.实验证明,微生物对污油确实存在较强的选择性降解消耗作用,可以减轻石油生产对土壤的破坏及对环境的污染.     

油气地质二元论与石油工业可持续发展

目的 为了开拓油气勘探的思路，探索油气勘探的新领域。方法 从油气地质二元论的思想出发，论述了陆壳结晶基底的通道．块状结构、无机油气的生成和裂谷盆地的形成过程。结果 中地壳费．托合成反应形成的烃类和盆地中干酪根热解生成的烃类是油气的两种来源；大油气田在平面上受通道．块状结构控制，在剖面上受圈闭控制，即更多的油气富集在超基性岩通道上方的圈闭中。结论 油气地质二元论可成为石油工业可持续发展的理论基础。     

论冀中地区O、C—P凝析气藏的形成条件

据凝析油轻烃组成、甲烷及其同系物碳同位素组成、天然气与源岩吸附气指纹时比、双环倍半萜组合特征及地质结构的综合分析,查明O、C—P大多数提析气藏的油气主要来源于石炭—二叠系煤系腐植型有机质,混入了部分下第三系的油气。对石炭—二叠系成烃特点的分析表明,R。=0.6%～1.3%,以成气为主,生油为辅,原始油气比一般大于1OOCm3/t。成熟期的石炭—二叠系有机质的成烃特点和具备油气富集的良好地质条件是O、C—P凝析气藏形成的基本条件。     

层序地层特征与油气成藏关系——以塔中4油田为例

 将层序地层学理论与油气成藏理论相结合,从层序特征、沉积体系和油气成藏条件等方面探讨了塔中4油田CI油组层序地层特征与油气成藏模式。综合利用地震、测井及岩心资料,开展塔中4油田CI油组层序地层学研究,将其划分为2个三级层序、5个准层序组、9个准层序。在层序地层格架内进行沉积特征研究,确立研究区发育潮坪和三角洲两类沉积体系。在层序及沉积特征研究基础上,对油气成藏的要素进行分析,确立沿断输导它源成藏模式。CI油组本身烃源岩不发育,油气主要来源于下覆奥陶和寒武统烃源岩。储集层主要分布在SQ1及SQ2的海侵体系域。油气从烃源岩中沿着大断裂向上运移到CI油组成藏,发育有岩性、断层-岩性及微背斜3种类型油气藏。     

注气驱油技术发展应用及海上油田启示

近年海上低渗油藏、稠油油藏储量占未动地质储量中比例逐年增加,如何有效地动用此类难动储量已成为研究的热点问题。注气驱油技术在国内外已经应用了数十年,而中国海上注气驱油技术尚处于起步阶段。针对这些问题,开展了国内外注气开发理论及应用的综述研究,结合中国海上油田的开发现状和生产难点,分析了海上注气驱油技术发展的7项制约因素,并探讨提出了拟解决措施和方法。研究表明,海上油田注气驱油技术应用潜力较大,关键技术的本土化及多手段联合应用可降低潜在开发风险,提高开发经济效益,对推动海上难动储量的有效动用具有重要意义。     

复杂断块油田油气不均一分布特征及主控因素

油气不均一分布是含油气盆地中油气分布的普遍规律,这在复杂断块油田尤为明显：同一复杂断块油田不同断块之间或不同层段之间的原油物性及油气富集程度差异较大;同一断块内由于储层非均质性及成岩作用不同,断块内部油气分布也存在不均一性;复杂断块油田油藏类型复杂多变,且多与断层相关。断–砂配置和断层性质的差异性是导致同一复杂断块油田的不同断块油气富集差异性的关键因素;断层规模、产状、力学性质以及断层的平面或剖面组合样式等,均对油气富集有着重要影响。运用“断块区控制油气富集区”的思想来指导油气勘探工作,可以起到良好的效果。     

网毯式油气成藏体系的动态平衡研究

根据动态平衡的概念,对东营凹陷网毯式体系中的结构、油气的输导、仓储和成藏的过程进行了研究。研究结果表明,仓储层作为连接油源通道网层和油气聚集网层的枢纽,对来自油源通道网层的油气起到临时的仓储作用。一部分油气通过仓储层的输导,在上部网层聚集成藏,另一部分油气可在仓储层中聚集成藏。仓储层输导和聚集油气是一个动态的过程,在某一个历史时期,它维持着油气运聚的动态平衡。在东营凹陷中、东部,仓储层发育,构造运动形成了多种空隙,并组成了多种类型的油气运移通道,故油气二次成藏的机会较多,是寻找他源隐蔽油气藏的重要区域,在今后的油气勘探中应引起足够的重视。