Migration and accumulation characteristics of natural gas hydrates in the uplifts and their slope zones in the Qiongdongnan Basin,China

Various factors controlling the accumulation of natural gas hydrates(NGHs)form various enrichment and accumulation modes through organic combination.This study mainly analyzes the geological and geophysical characteristics of the NGHs occurrence in the uplifts and their slope zones within the deep-water area in the Qiongdongnan(QDN)Basin(also referred to as the study area).Furthermore,it investigates the dominant governing factors and models of NGHs migration and accumulation in the study area.The results are as follows.(1)The uplifts and their slope zones in the study area lie in the dominant pressure-relief direction of fluids in central hydrocarbon-rich sags in the area,which provide sufficient gas sources for the NGHs accumulation and enrichment through pathways such as gas chimneys and faults.(2)The top and flanks of gas chimneys below the bottom simulating reflectors(BSRs)show high-amplitude seismic reflections and pronounced transverse charging of free gas,indicating the occurrence of a large amount of gas accumulation at the heights of the uplifts.(3)Chimneys,faults,and high-porosity and high-permeability strata,which connect the gas hydrate temperature-pressure stability zones(GHSZs)with thermogenic gas and biogenic gas,form the main hydrate migration system.(4)The reservoir system in the study area comprises sedimentary interlayers consisting of mass transport deposits(MTDs)and turbidites.In addition,the reservoir system has developed fissure-and pore-filling types of hydrates in the pathways.The above well-matched controlling factors of hydrate accumulation enable the uplifts and their slope zones in the study area to become the favorable targets of NGHs exploration.

Oil source and migration process in oblique transfer zone of Fushan Sag,northern South China Sea

The oblique transfer zone in the Fushan Sag, a syndepositional dome sandwiched between the Bailian and Huangtong sub-sags, has been the most important exploration target. The major oil observation occurs in the E_2l_1^(L+M) and the E_2l_3~U. 46 oil and rock samples reveal that the oil in the transfer zone is mostly contributed by the Bailian sub-sag, though the source rock conditions, hydrocarbon generation and expulsion histories of the Bailian and Huangtong sub-sags are similar. The E_2l_3~U oil, characterized by high maturity, Pr/Ph ratio and oleanane/C_(30)-hopane ratio, shows a close genetic affinity with the E_2l_3~b source rocks, while the E_2l_1^(L+M) oil, characterized by lower maturity, Pr/Ph ratio and oleanane/C_(30)-hopane ratio, is suggested to be derived from the E_2l_(1+2)~b source rocks. The homogenization temperatures of aqueous fluid inclusions, taking the burial history of the reservoirs into account, reflect that the oil charge mainly occurred from mid-Miocene to Pliocene in the oblique transfer zone. The oil transporting passages include connected sand bodies, unconformities and faults in the Fushan Sag. Of these, the faults are the most complicated and significant. The faults differ sharply in the west area, the east area and the oblique transfer zone, resulting in different influence on the oil migration and accumulation. During the main hydrocarbon charge stage, the faults in the west area are characterized by bad vertical sealing and spatially dense distribution. As a result, the oil generated by the Huangtong source rocks is mostly lost along the faults during the vertical migration in the west area. This can be the mechanism proposed to explain the little contribution of the Huangtong source rocks to the oil in the oblique transfer zone. Eventually, an oil migration and accumulation model is built in the oblique transfer zone, which may provide theoretical and practical guides for the oil exploration.

Mesh model building and migration and accumulation simulation of 3D hydrocarbon carrier system

Migration and accumulation simulation of oil and gas in carrier systems has always been a difficult subject in the quantitative study of petroleum geology. In view of the fact that the traditional geological modeling technology can not establish the interrelation of carriers in three dimensional space, we have proposed a hybrid-dimensional mesh modeling technology consisting of body(stratum), surfaces(faults and unconformities), lines and points, which provides an important research method for the description of geometry of sand bodies, faults and unconformities, the 3 D geological modeling of complex tectonic areas, and the simulation of hydrocarbon migration and accumulation. Furthermore, we have advanced a 3 D hydrocarbon migration pathway tracking method based on the hybrid-dimensional mesh of the carrier system. The application of this technology in western Luliang Uplift of Junggar Basin shows that the technology can effectively characterize the transport effect of fault planes, unconformities and sand bodies, indicate the hydrocarbon migration pathways, simulate the process of oil accumulation, reservoir adjustment and secondary reservoir formation, predict the hydrocarbon distribution. It is found through the simulation that the areas around the paleo-oil reservoir and covered by migration pathways are favorable sites for oil and gas distribution.

Fluid Potential Distribution and Oil & Gas Accumulation in Tertiary of Western Qaidam Basin

With the development of oil and gas exploration industry, researchers and engineers have realized that the key element controlling the migration of underground oil and gas and other fluid is not the pressure of stratum, but the underground fluid potential. Therefore, it is very crucial to study the distribution rule of fluid potential in order to correctly determine the exploration target areas. This paper studies the fluid potential distribution in Tertiary of west Qaidam Basin, puts forward the model of underground oil and gas migration and predicts the areas for further exploration.

Hydrocarbon Migration and Accumulation in Dongying Basin

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Forming mechanism of hydrocarbon reservoirs in Yingshan Formation of Yuqi block in Akekule arch,Tarim Basin

The reservoir conditions,oil and gas charge history and accumulation phases were studied for Yingshan Formation of Yuqi block,and an oil and gas accumulation model was established by using the techniques of reservoir prediction,fluorescence thin section and fluid inclusion analysis under the guidance of the theories of oil and gas accumulation.The results indicate that the main rock types in Yingshan Formation are micrite and calcarenite.The carbonate reservoirs are of cave,fracture-pore and fracture types,and their physical properties are intermediate;there are at least four oil/gas charges,i.e.late Hercynian,Yanshanian,early Himalayan and middle Himalayan(Cenozoic).The most important charge periods are late Hercynian,early Himalayan and middle Himalayan;the oil and gas accumulation model is self source-lateral expulsion of hydrocarbon-multistage accumulation,or hydrocarbon sourced from and preserved in the same old rocks-long term expulsion of hydrocarbon-multistage accumulation.

Basic principles of the whole petroleum system

This paper expounds the basic principles and structures of the whole petroleum system to reveal the pattern of conventional oil/gas-tight oil/gas-shale oil/gas sequential accumulation and the hydrocarbon accumulation models and mechanisms of the whole petroleum system.It delineates the geological model,flow model,and production mechanism of shale and tight reservoirs,and proposes future research orientations.The main structure of the whole petroleum system includes three fluid dynamic fields,three types of oil and gas reservoirs/resources,and two types of reservoir-forming processes.Conventional oil/gas,tight oil/gas,and shale oil/gas are orderly in generation time and spatial distribution,and sequentially rational in genetic mechanism,showing the pattern of sequential accumulation.The whole petroleum system involves two categories of hydrocarbon accumulation models:hydrocarbon accumulation in the detrital basin and hydrocarbon accumulation in the carbonate basin/formation.The accumulation of unconventional oil/gas is self-containment,which is microscopically driven by the intermolecular force(van der Waals force).The unconventional oil/gas production has proved that the geological model,flow model,and production mechanism of shale and tight reservoirs represent a new and complex field that needs further study.Shale oil/gas must be the most important resource replacement for oil and gas resources of China.Future research efforts include:(1)the characteristics of the whole petroleum system in carbonate basins and the source-reservoir coupling patterns in the evolution of composite basins;(2)flow mechanisms in migration,accumulation,and production of shale oil/gas and tight oil/gas;(3)geological characteristics and enrichment of deep and ultra-deep shale oil/gas,tight oil/gas and coalbed methane;(4)resource evaluation and new generation of basin simulation technology of the whole petroleum system;(5)research on earth system-earth organic rock and fossil fuel system-whole petroleum system.

Kinetics of hydrocarbon generation for Well Yingnan 2 gas reservoir,Tarim Basin,CHina

Well Yingnan 2,an important exploratory well in the east of Tarim Basin,yields high commercial oil and gas flow in Jurassic.Natural gas components and carbon isotopic composition indicate that it belongs to sapropel type gas.Because this region presents many suits of hydrocarbon source rocks,there are some controversies that natural gases were generated from kerogen gas or crude oil cracking gas at present.By using the kinetics of hydrocarbon generation and carbon isotope,natural gas of Well Yingnan 2 is composed mainly of crude oil cracking gas,about 72%,it is generated from secondary kerogen gas of Cambrian-Lower Ordovician source rock and crude oil cracking gas of Mid-Upper Ordovician oil reservoir.The main oil and gas filling time is 65 Ma later in the Jurassic gas reservoir of Well Yingnan 2,so the gas reservoir belongs to late accumulation and continuous filling type.

Hydrocarbon migration in fracture-cave systems of carbonate reservoirs under tectonic stresses:A modeling study

The Tahe oilfield,located in the southwest of the Akekule nosing structure,northern Tarim basin,was the most prolific oilfield targeting at the Ordovician carbonate reservoirs in China.The reservoir space was dominant with fracture-cave systems commonly induced by tectonics and karstification.Although hydrocarbon production had proceeded for two decades in the Tahe oilfiled,the control of oil and gas accumulations was still doubtful.In this work,the periodic fluid flow induced by cyclic tectonic stresses was proposed as the mechanism of hydrocarbon migration in the fracture-cave systems of carbonate reservoirs.The fracture networks formed conduits for fluid flow,and the fluid pressure in caves transmitted from stress field provided the driving force.The constitutive equations were established among stresses,fracture densities and flow velocities.Four quasi-3D geological models were constructed to simulate the flow velocities on the Ordovician surface of Akekule nosing structure in the critical tectonic stages.The simulated results supplied indicative information on oil and gas migration and accumulation in the tectonic stages.Combining with the oil and gas charge history,a conceptual model was built to reveal the multi-stage oil and gas charge and accumulation in the Ordovician of Akekule nosing structure.

济阳坳陷孤南洼陷低熟油成藏特征

孤南洼陷具有丰富的低熟油资源 .低熟油中的生物标志物以高伽玛蜡烷含量、植烷优势、低成熟度为特征 .下第三系沙一段是低熟油的源岩 ,其岩性为富含藻类有机质的油页岩、油泥岩 .低熟油在平面上环生烃洼陷分布 ,剖面上层位集中在沙二—沙一段 .断层控制了低熟油的运移距离和聚集层位 .低熟油的成藏模式有 3种 ,即自源侧向运移聚集成藏、自源断层垂向运聚成藏和混合运聚成藏模式 .孤南洼陷低熟油在盆地内部以侧向运移、侧向充注入岩性 -断块圈闭为主 ,形成单源油藏 .在断裂带原油是以垂向运移及垂向充注断块圈闭为主 ,形成混源油藏 .

准噶尔盆地玛北斜坡带油气成藏研究

对风城油田和玛北油田进行成藏分析,认为烃源岩主要为玛湖凹陷的二叠系风城组,其次为佳木河组;输导层主要为断层、层内渗透层和不整合面;两个成藏期分别是三叠纪末和侏罗纪末—白垩纪;存在两种类型的成藏模式,一是三叠纪—源内—不整合—断控原生油气藏成藏模式;二是侏罗-白垩纪—源上—不整合—断控次生油气藏成藏模式。在此基础上,通过对烃源岩、储集层、盖层、圈闭条件的研究,指出乌尔禾油田—夏子街油田—玛北油田接合部P-J地层油气藏为下一步勘探方向。

柴达木盆地西部第三系异常高压与油气成藏

柴达木盆地在一定深度及区域上普遍存在异常高压。一方面 ,异常高压是油气运聚的一种重要动力来源 ;另一方面 ,异常高压在一定地质背景下是控制油气分布的重要因素。在油气运移中 ,可以使上覆封隔层产生大量微裂缝 ,油气向上运移到在较低压储集层中 ,也可以使封闭性断层开启 ,通过断层进行侧向运移 ;异常高压形成的流体势能驱动流体从凹陷中心向凹陷边缘流动 ,最终形成油气藏围绕生油凹陷分布的格局。该区与异常压力有关的油气成藏模式可以概括为 3种类型 ,即 :位于异常高压体系内部裂缝型高压油气藏 ,异常高压体系下部孔隙型高压油气藏 ,位于封隔层之上的孔隙型常压油气藏。

八面河油田油气运聚、成藏模式探讨

八面河油田原油中吡咯类化合物及与其具有类似骨架的杂原子芳烃—二苯并噻吩、二苯并呋喃等具有较为明显的运移分馏效应 ,指示八面河断裂构造带中北部断裂、构造较为发育地带为主要油气注入点 ,绝大部分油气自主要注入点沿地层上倾方向作侧向运移 ;广北斜坡带运移分馏效应不太明显 ,反映各油气单元间连通性较差及油源、油气运聚成藏过程较为复杂 ;滩海一带原油具有较强的运移分馏效应 ,指示原油具有非原地性 .含氮化合物运移分馏效应反映 ,断层、不整合面为八面河油田油气运移的主要通道 ,牛庄、广利洼陷为八面河油田可能的油源区 ,反映绝大多数油气主要来自正常生油门窗内的成熟烃源岩 .

断裂带作为油气散失通道的输导能力

通过断裂散失的油气量主要与断裂带的输导能力、实际进入断裂带的油气量、断裂通道的长度、散失时间和储层分流系数等参数有关。断裂带输导能力的主要因素是断裂带的宽度和储层渗透率。利用断裂散失模型计算了不同规模的断裂带作为油气散失通道的输导能力。计算结果表明 ,大型断裂带输导油气的能力远大于储层输导油气的能力。断裂活动期进入“通天”大断裂带的油气主要趋于散失 ;小断裂由于储层的分流作用 ,即使在活动期 ,它作为油气散失通道的作用也是有限的 ,其油气的散失量可以忽略不计。

准噶尔盆地南缘卡因迪克地区油气成藏模式研究

以油气藏形成的静态要素为基础、以各要素的动态演化过程为主线，通过生物标志化合物对比、烃源岩热演化、流体包裹体分析以及典型油气藏解剖，厘清了准噶尔盆地南缘卡因迪克地区油气来源、成藏过程，建立油气成藏模式。卡因迪克地区原油可分为3类，分别源自侏罗系煤系地层、古近系湖相泥岩以及二者混源，以侏罗系油源为主。该地区主要接受了2期油气充注，分别距今10～8 Ma和2 Ma左右，第二期充注包含第一期充注所形成古油藏的调整。卡因迪克地区砂层主要受北部物源控制，与南部连通性差，油气在侧向上主要通过区域性不整合运移，断层是沟通深部油源及古油藏调整的关键因素。在断裂和背斜的双重控制下，油气藏类型以断控-挤压型背斜油气藏为主，成藏主控因素为沟通烃源的断层，成藏模式为混源、垂向运移为主、2期成藏、晚期为主。

苏北盆地溱潼凹陷油气运聚模式

通过对苏北盆地溱潼凹陷不同构造带部分具代表性油藏原油的饱和烃、芳烃生物标志物和吡咯类含氮化合物分布特征的分析,结合油区构造研究和油源对比成果,讨论了研究区油气的运移方向与运聚模式。结果表明,研究区不同构造带原油中吡咯类含氮化合物分馏效应存在差别,处于断阶带南侧的成熟原油运移效应明显,来源于其西北侧的俞垛次凹始新统阜宁组二段烃源岩;断阶带北侧的原油运移分馏效应较差,推测其主要来源于北侧的储家楼次凹阜宁组二段烃源岩,以短距离侧向运移为主;内斜坡带原油主要来自于储家楼深凹阜宁组二段烃源岩,沿其构造带上倾方向自西南到东北方向,含氮化合物分馏效应明显;坡垒带与外斜坡带阜宁组三段原油成熟度偏低,吡咯类含氮化合物浓度较高,原油自东北向西南方向以短距离运移为主,主要来自于深凹的低熟烃源岩。不同构造带的油气成藏模式也不一致,断阶带为阶梯状断块油气聚集模式,内斜坡带与坡垒带主要分布受断层控制的断块—岩性油藏,外斜坡带为反向正断层垒块控油模式。

三维油气输导体系网格建模与运聚模拟技术

油气在输导体系中的运聚模拟一直是石油地质定量化研究中的难题。针对传统地质建模技术不能在三维空间中建立输导体相互联系的现状,采用混合维数网格建模思路,形成一种由体(地层)、面(断裂面和不整合面)、线和点构成的混合维数网格建模技术,为砂体、断面和不整合面几何形态的刻画、复杂构造区三维地质建模以及油气运聚模拟提供重要的研究手段,并提出了一种基于输导体系混合维数网格的三维油气运移路径追踪方法。准噶尔盆地陆西地区的应用实例显示,该技术能够有效刻画断层面、不整合面和砂体的输导作用,透视油气运移路径,模拟石油聚集、油藏调整及次生油藏的形成过程,揭示油气分布规律,指出古油藏附近和运移路径所覆盖的区域是油气分布有利区。

济阳坳陷精细勘探新成果与启示

济阳坳陷历经50多年的勘探,整体进入隐蔽油藏勘探阶段。"十二五"期间,面对日趋复杂的勘探对象,勘探工作者围绕高效勘探目标,客观分析资源现状,积极改进地震资料品质,厘清中浅层地质认识瓶颈问题,以基础认识创新引领老区新的突破,构建新的地质模型以挖掘成熟区带新的潜力。针对勘探瓶颈地区、盆缘地层油藏、新近系河道砂岩性油藏、深层区块等潜力方向,通过重新构建早期油气运聚模型、多级序地层不整合圈闭模型、河道砂岩油藏描述模型、复杂断裂带构造模型和陡坡砂砾岩评价模型进行精细勘探,发现了青南油田和三合村油田,取得了14个预探重大突破,落实了12个千万吨级规模经济储量阵地。"十二五"勘探实践表明,"成熟"探区不"成熟","经验"突围有"资源",老区仍然蕴藏着丰富的油气资源,以创新为引领,精细研究,勇于探索,老区仍能大有作为。

大港油田埕北断阶带油气运移、成藏期次及成藏模式

通过原油中类异戊二烯烃地球化学变化特征的对比分析,指出大港油田埕北断阶带的油气主运移方向是由北边的生油凹陷(歧口凹陷)向南(埕北断阶带)运聚和由西边的生油凹陷(歧南凹陷)向(北)东(张东地区、关家堡地区和埕海地区)运聚。利用流体包裹体、生排烃法、饱和压力法等方法技术,认为存在两个充注期:古近纪东营末期和新近纪明化镇末期—第四纪。结合输导体系研究成果,提出了4种油气成藏模式:沿连通砂体—不整合面侧向运聚成藏模式、沿断层垂向运聚成藏模式、沿连通砂体(不整合面)—断层阶梯状运聚成藏模式、源内砂岩透镜体运聚成藏模式。