INTEGRATION OF BIODEGRADATION AND MIGRATION OF HYDROCARBONS IN A 2D PETROLEUM SYSTEMS MODEL: APPLICATION TO THE POTIGUAR BASIN,NE BRAZIL

Biodegradation is probably the most important in‐reservoir alteration process and is responsible for the majority of the known heavy oil accumulations. In the present study, biodegradation processes were integrated within a forward basin and petroleum systems model applied to the Potiguar Basin, NE Brazil. This basin was chosen because it has been studied in detail and data from previous investigations are publically available. In order to account for processes occurring during the biodegradation of hydrocarbons, the evolution of fluid properties was simulated through time. In the model, a new approach was developed in order to determine the intensity of microbial activity and the evolution of the oil‐water contact, the zone within which biodegradation is confined. The numerical results obtained by applying the forward simulator to a 2D model of the Potiguar Basin fit the observed data concerning the composition and quality of the oil in a series of oilfields. These accumulations are located along the NE‐SW oriented “Carnaubais trend” and show progressive biodegradation along the migration path from the offshore kitchen area. Our results show that the biodegradation trend observed along the cross‐section can in general be explained by the fact that reservoirs are successively filled as a result of spilling from previous reservoirs, with continuous hydrocarbon degradation occurring within the reservoirs. This charge history resulted in differences in the composition of oils transported from upstream to downstream reservoirs, and in the evolution over time of the ratio between biodegradation and reservoir filling rates. Thus, in addition to residence time in the biodegradation temperature window, the rate of reservoir infill, the rate of oil degradation and the migration pathways are key factors controlling biodegradation. This study also demonstrates how the approach developed within our petroleum system simulator, which integrates both migration and biodegradation, may improve the assessment of oil quantity, quality and migration timing.     

塔河油田奥陶系油气地球化学特征与油气运移

通过对塔河油田奥陶系油气地球化学特征与油气运移关系的研究,认为:a)油气物理性质可以宏观地反映油气运移的方向;b)原油轻烃、生物标记物和含氮化合物可以较好地反映油气运移方向,饱和烃生物标记化合物反映了相对轻质原油的油气运移方向,含氮化合物则主要反映了相对早期原油的运移方向;c)塔河油区存在着早期由南向北、晚期由南向北、由东向西的油气运移充注过程.      

THE PETROLEUM SYSTEM IN THE SANDINO FOREARC BASIN, OFFSHORE WESTERN NICARAGUA

The underexplored Sandino Basin (Nicaragua Basin/Trough) is located within the forearc area of western Nicaragua and NW Costa Rica. Exploration activity since 2004 has focussed on the onshore sector of the basin, and has included the first drilling campaign for over 30 years. Recent 2D basin modelling of the offshore sector together with organic geochemical studies has attempted to reassess the basin's petroleum potential. Geochemical data from the deepest offshore well indicate that Middle Eocene to Lower Oligocene sediments of the Brito Formation, as well as Upper Oligocene to Lower Miocene sediments of the Masachapa Formation, may have source rock potential. A third and perhaps more significant potential source rock interval is associated with the Lower Cretaceous black shales of the Loma Chumico Formation, which has been studied in the adjacent forearc area in NW Costa Rica (Tempisque Basin) and is inferred to be present in the Sandino Basin.
The thermal history of the forearc basin is controlled by the low basal heat flow (39 mW/m²). 2D modelling has shown that the Sandino Basin is thermally mature, resulting in the potential for hydrocarbon generation in organic-rich intervals in the Brito and Masachapa Formations. A petroleum-generating "kitchen" has tentatively been identified on a NE-SW seismic section which crosses the basin. Modelling suggests that this kitchen has been active from the Late Eocene until the present day, and that the main phases of petroleum generation in general coincide with phases of maximum subsidence in the Late Eocene, Late Oligocene and Plio-Pleistocene. Hydrocarbon migration most probably occurred from the deep basin towards the flanks. Significant volumes of petroleum may have been lost prior to the Late Miocene before the formation of a coastal flexure which can be recognised in the NE of the seismic profile.     

济阳坳陷内的负反转构造及其石油地质意义

济阳坳陷是中国东部一个重要的中新生代含油气盆地,过去一直认为该盆地为纯张裂成因,但近来盆地内负反转构造的发现和研究表明,该盆地在中生代发育早期曾经历了负反转、正反转交替的发育阶段,并总体呈现为负反转盆地特征。本文研究了负反转构造的类型和特征,识别出“薄底型”和“秃底型”两类负反转褶皱和“似正断层型”、“上正下逆混合型”等两类、4小类负反转断层;探讨了盆地与负反转构造的形成与演化,并指出了其在盆地成因、构造带演化、复式油气聚集带型式及油气藏形成与预测等诸多方面具有的重要意义。     

鄂尔多斯镇泾地区延长组成藏体系与油气富集模式

在典型油藏解剖基础上,根据油气成藏体系概念和划分原则,结合烃源岩、源储组合样式、油藏特征、成藏机制等,将镇泾地区延长组划分为近源—接触式成藏体系和近源—跨越式成藏体系2类。前者油藏类型以岩性油藏为主,源储紧邻,为直接接触,具有"近源成藏"特征,运移距离短,运移动力主要为源储压力差,输导体系为砂岩(微裂缝),隐性输导,油气富集主控因素为优质烃源岩、有利砂体和裂缝,油气富集模式可概括为"近源—接触式'源、相、缝'控";后者油藏类型以构造—岩性为主,源储为跨越式接触关系,具有"远源成藏"特征,运移距离较长,运移主要动力为源储压力差和浮力,输导体系以断裂—砂体为主,油气富集主控因素为通源断裂、有利砂体和裂缝,富集模式可概括为"近源—跨越式'断、相、缝'控"。     

中国复合含油气系统的基本特征与勘探技术

中国叠合含油气盆地具有演化历史长、沉积层系多、构造变动强烈等特点。其中发育的含油气系统常表现出多源多灶多期生烃与运聚成藏以及成藏后多期调整改造的复杂性,形成过程有多个关键时刻,而且由于断层、不整合、砂体和裂缝等通道的连接作用,系统之间可发生烃类流体交换,形成多源油气的混合聚集。鉴于中国含油气系统的复杂性,提出复合含油气系统的概念,并总结其基本特征、描述方法和勘探技术。建议从生烃灶确定开始,以顺藤摸瓜的方式,确定不同关键时刻,理清各成藏地质要素特征与空间组合关系,指出油气运移和聚集的空间范围。流体历史分析与盆地模拟等现代勘探技术的配套使用在复合含油气系统描述与评价中发挥着重要作用。     

热作为油运移动力的物理模拟实验

针对不同物性输导体、不同供油条件、不同温度差作用下油的运移情况进行了5组模拟实验。结果表明在温度差作用下油流体可以发生运移,证实热(温度)在一定条件下可以作为流体运移的直接动力。在实验条件下,温度差(热)是决定油运移进行与否、运移速度、运移距离大小的最主要因素。在其他条件相同的情况下,温差越大,运移距离越长;干砂中比湿砂中运移距离长;两端加热比一端加热运移距离长;一端开放更有利于油运移;不断补给供油量并不能使运移距离增大;储层物性并不影响油运移距离。     

老爷庙地区石油地质特征与油气分布

老爷庙构造带为一滚动背斜构造带,发育3个级别的断层:(1)EWNE走向的控凹断层;(2)NNENE走向的控油断层;(3)NW-NW-W走向的控圈闭断层。沙河街组三段4～5亚段的深湖相泥岩及沙河街组一段至东营组三段的浅湖半深湖相泥岩为主力生油岩,此二套生油岩已进入成熟阶段,有机质类型以混合型及腐殖型为主,均具较高丰度,为较好好生油岩。辫状河道砂体、水下重力流砂体、水下分流河道砂体、河口坝砂体及深水浊积砂体为主要储集体,具高孔、高渗特征。油气藏的类型主要受控于裂陷盆地的伸展程度、同生断层及沉积相带。裂陷旋回控制含油气系统的分布,同生断层使含油面积扩大,储集体相带的配置决定油气的富集程度。     

PETROLEUM SYSTEMS: MODELS AND APPLICATIONS

The term "petroleum system"— barely twenty years old — incorporates a new view of the formation of hydrocarbon accumulations. The concept is based on an orderly sequence of geological phenomena, starting with the genesis of oil or gas, which then migrates and is finally trapped. This sequence of events depends closely on the geodynamics of the sedimentary basin, which is determined by global plate-tectonics.
The main petroleum system models can therefore be defined in terms of the major types of basin. There are three main systems—continental rift, platform, and orogenic—each of which has a number of variants: continental rifts provide good conditions for oil generation, vertical migration and accumulation at various levels; by contrast, platform systems encourage the formation of reservoirs at the expense of source rocks and long, lateral migration paths, which frequently form tar-belts; and orogenic systems encourage entrapment in zones little affected by tectonic movements, accompanied by frequent surface shows.
The "petroleum system" concept describes the dynamic, mobile formation of petroleum pools, and has a number of implications for exploration strategy.     

玛湖-盆1井西复合含油气系统低压特征与成因

随着油气勘探的不断深入，已在越来越多的沉积盆地中发现了低压现象，但对低压成因及其与油气运聚分布关系的研究则显得不足。玛湖-盆1井西复合含油气系统是准噶尔盆地油气分布最集中的地质单元，研究表明该系统地层中高压和低压均存在，侏罗系及以上地层中多低压，且在气藏分布区低压更突出，形成较开放性的压力系统。随着盆地的形成演化，异常地层压力亦有产生、发展和消亡的过程。玛湖-盆1井西复合含油气系统中低压的形成与油气运移过程中轻烃组分的漏失量大于油气和地下水的运移补给量，同时盆地抬升剥蚀和地温的持续下降，进而造成地层中能量亏损有关，而低压的形成时间则应该在古近纪。     

广西百色盆地油气系统

广西百色盆地是在海相中三叠统基底上发育起来的第三纪陆相断陷盆地。对盆地油气系统要素进行了深入分析,用“四图一表”表示。研究结果表明,盆地内存在那读组和百岗组2套烃源岩,有较好的储集层和3套盖层以及较厚的上覆岩层,生储盖组合良好,但盆地成型后的构造作用使其保存条件遭到了极大破坏,因此勘探实践揭示的油气情况并不十分理想。     

对叠合型盆地油气系统研究方法和分类问题的思考

在前人研究的基础上,探讨叠合型盆地油气系统分析的思路、流程和研究内容,强调在进行油气系统划分前,要对盆地的构造格架、沉降充填史、热过程以及盆地的构造单元、烃源岩发育的层段和范围、生储盖组合的基本特征,做系统的分析和评估,再在油气源对比的基础上对油气系统进行划分。鉴于叠合盆地存在多套烃源岩、多个生烃单元,断裂和不整合发育,认为叠合型油气系统的划分应以烃源岩+构造单元(生烃凹陷或洼陷及油气可能的运聚区域)为最主要依据,以烃源岩+构造单元+可靠程度来进行命名比较合适,也较为实用。叠合型油气系统分析要从静态地质要素分析和动态地质过程分析2个方面进行,静态地质要素包括有效的烃源岩、储集层、盖层、输导层和圈闭,动态地质要素包括油气生成过程、储层演化过程、油气运移过程、圈闭形成过程、油气成藏过程等。各要素组合关系分析、油气系统保存作用分析、各油气系统叠合关系分析、勘探有利靶区及目标分析等都是叠合型盆地油气系统研究内容的组成部分。     

中国西部多旋回演化与油气聚集

由额尔齐斯—得尔布干、康西瓦—龙木错—澜沧江两大岩石圈断裂所限定的广大西北地区的区域构造格架是由哈萨克斯坦板块和古中华陆板块中大小不等、属性不同的古陆块与多旋回造山带镶嵌交错排列而成,具有南北分带、东西分块特点。以海西早期运动、海西晚期运动、燕山中期运动为界线将西部区域构造与盆地演化划分为古亚洲洋体制下的震旦—中泥盆世开合旋回、古特提斯洋体制下的晚泥盆—中二叠世开合旋回、特提斯洋体制下的晚二叠世—晚侏罗世盆地旋回和现今大洋体制下的白垩纪以来的盆地旋回。按盆地的旋回性和改造程度可将西部盆地群分为弱改造多旋回盆地等六类。针对多旋回盆地多期形成的多种烃源在空间上并列、叠置、交错的复杂状况和复杂沉降及热体制下的多期生烃、排烃及运聚保存过程,完善了已有的复式油气系统的概念和分析内容,提出了油气成藏单元的概念并用于对复式油气系统内部不同部位成藏要素与过程的总结。在对已知油气藏解剖的基础上,系统分析了两大盆地中主要油气聚集带成藏的静态条件与动态过程,分别建立了成藏模式,强调西部油气聚集具有多源多期多灶供烃,两大类多成因储层和封闭系统形成、破坏与重建构成多种储盖组合,不同区带具有多类型圈闭纵、横向空间组合样式,存在多期聚集、破坏、调整等复杂过程。初步形成了从"古亚洲域和特提斯域的区域控制→多旋回盆地演化与多变的叠加改造方式→多源多期生烃形成多相态油气→复式油气系统中多类复式油气聚集带"的理论脉络。     

应用“聚油单元”研究济阳坳陷的石油资源潜力

在济阳坳陷下第三系石油资源评价中,根据"含油气系统——从烃源岩到圈闭"的基本研究思路,加强主运移通道控烃的研究,提出了"聚油单元"的概念,强调"聚油单元"是盆地数值模拟和资源潜力分析的基本单元.根据研究,将济阳坳陷划分为28个聚油单元,并在盆地数值模拟和排、聚系数研究的基础上,计算了各聚油单元的资源量.从石油资源量、远景石油资源量和远景石油资源丰度等方面分析了各聚油单元的资源潜力后认为,济阳坳陷在新领域、新层系和新类型的石油勘探潜力仍然很大.      

三江盆地石油地质条件与勘探前景

三江盆地作为我国东部中生界唯一的海相和海陆交互相沉积盆地,受早白垩世末构造运动的强烈改造,其原型盆地与现今残留盆地存在较大差异,有机质热演化已达成熟—高成熟演化阶段;发育上侏罗统、下白垩统和第三系三套烃源岩,油气源较丰富;多期构造运动和火山活动,形成的两组断裂以及不整合面,为油气运移提供良好的通道和运移动力;圈闭类型较多,定型早,与油气生排烃期形成良好的匹配关系;存在西部、东部两类不同成藏组合的勘探领域,具有较好的勘探前景。     

SUBSIDENCE, SEDIMENTATION AND PETROLEUM SYSTEMS

Analysis of a number of petroleum provinces has emphasised the importance of sedimentary factors as well as subsidence processes. Subsidence appears to depend on a small number of mechanisms - tectonics, heat flow and gravity. Taking into account thegeodynamic context in which these processes develop, it is possible to compile a classification of subsidence types which is distinct from the usual classifications in terms of basins. The type of subsidence influences the deposition rate, which determines both the potential and the habitat of petroleum. Moreover, existing statistics sho w that the number of "giant"fielako, r thep otential of a petroleum province largely depend on the types of subsidence and subsequent tectonic processes.
However, it is also important to consider the history of a basin in terms of flows: geothermal flows from the mantle and crust; and water and hydrocarbon flows through the sedimentary volume. For these flow transfers, climatic and sedimentary factors, as well as variations in sea level, play a role which is as important as subsidence and uplift in controlling the distribution of non-deposition areas, unconformities, seals and reservoirs. For example, periods of generalized transgression are favorable to both the development of carbonate platforms, and the formation of impervious horizons, seals and source rocks capable of sealing pre-existing rifts.
Therefore, a petroleum province can be considered as the final result of an organized set of geological events (in space and in time) that can be called apetroleum system. In such a system, thesequence ofsubsidencemovements and associatedflows isjust asdecisiveas lithological and geometric factors in the formation of a group of pools. This concept of the succession of geodynamics and sedimentary processes which affect petroleum potential is developed, and specific examples of petroleum systems from the North Sea, the Arabian Platform and the Congo Basin are presented.     

准噶尔盆地东南部油气地质条件研究

准噶尔盆地东南部发育了3套盆地原型,即P₂—T_2-3的后裂谷期充填盆地、T₃³—J_1-2的裂谷后前渊盆地、J₃—E的陆内前陆盆地的并列叠加作用;发育了3套主力生油岩系,即上二叠统芦草沟组、红雁池组和上三叠统黄山街组、郝家沟组及下、中侏罗统八道湾组、三工河组、西山窑组,并赋存于阜康凹陷、吉木萨尔凹陷、五彩湾凹陷、黄草湖凹陷之中,形成了多个供油中心。生储盖分析表明,该区油气保存条件良好,并具备在不同区块分别勘探油和油气的特点。构造分析表明,博格达推覆构造和2组(近南北向和近东西向)断块构造与油气生成、运移、聚集关系密切。综合分析表明,该区油气成藏地质条件较好,是值得进一步工作的领域。     

鄂南地区中生界油气成藏体系划分与富集区预测

在典型油藏解剖的基础上,根据油气成藏体系概念和划分原则,结合烃源岩、源-储组合样式、油藏特征和成藏机制等,将鄂南地区中生界划分为近源成藏体系和远源成藏体系两类。前者油藏类型以岩性油藏为主,具有"近源成藏"特征,运移距离短,运移动力主要为异常压力,隐性输导,油气富集主控因素为优质烃源岩、有利储集体和构造背景,油气富集模式可概括为"近源相控";后者油藏类型以构造、构造-岩性油藏为主,具有"远源成藏"特征,运移距离长,运移主要动力为浮力,输导体系以通源断裂为主,油气富集主控因素为通源断裂、局部构造和有利砂体,富集模式可概括为"远源断控"。近源成藏体系源储空间呈"三明治"结构,直接大面积接触,具有"近水楼台"成藏优势,生烃高峰期与关键成藏期一致,油气就近大面积充注成藏,是下一步勘探首选领域。其中,长₉-长₈-长₇近源成藏体系Ⅰ类富集有利区是大中型油气田重要的勘探方向。     

珠江口盆地番禺低隆起—白云凹陷北坡断层与油气成藏关系

综合运用断层分类、断层活动史分析、油藏充注史分析等方法，对珠江口盆地番禺低隆起-白云凹陷北坡地区断层与油气成藏关系进行了研究。该区发育两种类型断层：长期活动断层及晚期断层，这两种断层活动期与油气充注期匹配关系均较好，推断二者在油气充注史中起了相似的作用。勘探实践和各种证据表明，该区断层是油气垂向输导的主要通道，现今的静态的断层封闭作用控制了新近系目的层的油气成藏，而岩性对接情况是该区断层静态封闭性的主要控制因素。根据分析结果，建议该区勘探应加强目的层顶面演化特征研究、落实圈闭和断层封闭性，位于油气运移路径上且断层封闭性有效的圈闭，勘探获得成功的可能性较大。图8表1参11     

构造演化与含油气系统的形成——以准噶尔盆地东部吉木萨尔凹陷为例

准噶尔盆地东部自晚石炭世洋壳消减后进入陆相盆地演化阶段,是一个构造演化复杂、由多个含油气凹陷和凸起构成的构造带,其构造演化历史主要分为4个阶段,即裂谷—断陷盆地阶段、断—坳盆地阶段、陆内坳陷盆地阶段和再生前陆盆地阶段。结合盆地东部吉木萨尔凹陷复合含油气系统特征,探讨了构造演化与含油气系统形成之间的关系。研究表明,构造演化在一定程度上控制着生储盖组合的形成,影响烃源岩的演化进程,控制着含油气系统的多期生烃和多期成藏,构成含油气系统的运聚、改造和后期保存的关键时刻。