The mechanism of unconventional hydrocarbon formation: Hydrocarbon self-sealing and intermolecular forces

The successful development of unconventional hydrocarbons has significantly increased global hydrocarbon resources, promoted the growth of global hydrocarbon production and made a great breakthrough in classical oil and gas geology. The core mechanism of conventional hydrocarbon accumulation is the preservation of hydrocarbons by trap enrichment and buoyancy, while unconventional hydrocarbons are characterized by continuous accumulation and non-buoyancy accumulation. It is revealed that the key of formation mechanism of the unconventional reservoirs is the self-sealing of hydrocarbons driven by intermolecular forces. Based on the behavior of intermolecular forces and the corresponding self-sealing, the formation mechanisms of unconventional oil and gas can be classified into three categories:(1) thick oil and bitumen, which are dominated by large molecular viscous force and condensation force;(2) tight oil and gas, shale oil and gas and coal-bed methane, which are dominated by capillary forces and molecular adsorption;and(3) gas hydrate, which is dominated by intermolecular clathration. This study discusses in detail the characteristics, boundary conditions and geological examples of self-sealing of the five types of unconventional resources, and the basic principles and mathematical characterization of intermolecular forces. This research will deepen the understanding of formation mechanisms of unconventional hydrocarbons, improve the ability to predict and evaluate unconventional oil and gas resources, and promote the development and production techniques and potential production capacity of unconventional oil and gas.

Research advances on the mechanisms of reservoir formation and hydrocarbon accumulation and the oil and gas development methods of deep and ultra-deep marine carbonates

Based on the new data of drilling, seismic, logging, test and experiments, the key scientific problems in reservoir formation, hydrocarbon accumulation and efficient oil and gas development methods of deep and ultra-deep marine carbonate strata in the central and western superimposed basin in China have been continuously studied.(1) The fault-controlled carbonate reservoir and the ancient dolomite reservoir are two important types of reservoirs in the deep and ultra-deep marine carbonates. According to the formation origin, the large-scale fault-controlled reservoir can be further divided into three types:fracture-cavity reservoir formed by tectonic rupture, fault and fluid-controlled reservoir, and shoal and mound reservoir modified by fault and fluid. The Sinian microbial dolomites are developed in the aragonite-dolomite sea. The predominant mound-shoal facies, early dolomitization and dissolution, acidic fluid environment, anhydrite capping and overpressure are the key factors for the formation and preservation of high-quality dolomite reservoirs.(2) The organic-rich shale of the marine carbonate strata in the superimposed basins of central and western China are mainly developed in the sedimentary environments of deep-water shelf of passive continental margin and carbonate ramp. The tectonic-thermal system is the important factor controlling the hydrocarbon phase in deep and ultra-deep reservoirs, and the reformed dynamic field controls oil and gas accumulation and distribution in deep and ultra-deep marine carbonates.(3) During the development of high-sulfur gas fields such as Puguang, sulfur precipitation blocks the wellbore. The application of sulfur solvent combined with coiled tubing has a significant effect on removing sulfur blockage. The integrated technology of dual-medium modeling and numerical simulation based on sedimentary simulation can accurately characterize the spatial distribution and changes of the water invasion front.Afterward, water control strategies for the entire life cycle of gas wells are proposed, including flow rate management, water drainage and plugging.(4) In the development of ultra-deep fault-controlled fractured-cavity reservoirs, well production declines rapidly due to the permeability reduction, which is a consequence of reservoir stress-sensitivity. The rapid phase change in condensate gas reservoir and pressure decline significantly affect the recovery of condensate oil. Innovative development methods such as gravity drive through water and natural gas injection, and natural gas drive through top injection and bottom production for ultra-deep fault-controlled condensate gas reservoirs are proposed. By adopting the hierarchical geological modeling and the fluid-solid-thermal coupled numerical simulation, the accuracy of producing performance prediction in oil and gas reservoirs has been effectively improved.

Dynamic Field Division of Hydrocarbon Migration,Accumulation and Hydrocarbon Enrichment Rules in Sedimentary Basins

Hydrocarbon distribution rules in the deep and shallow parts of sedimentary basins are considerably different, particularly in the following four aspects. First, the critical porosity for hydrocarbon migration is much lower in the deep parts of basins： at a depth of 7000 m, hydrocarbons can accumulate only in rocks with porosity less than 5%. However, in the shallow parts of basins （i.e., depths of around 1000 m）, hydrocarbon can accumulate in rocks only when porosity is over 20%. Second, hydrocarbon reservoirs tend to exhibit negative pressures after hydrocarbon accumulation at depth, with a pressure coefficient less than 0.7. However, hydrocarbon reservoirs at shallow depths tend to exhibit high pressure after hydrocarbon accumulation. Third, deep reservoirs tend to exhibit characteristics of oil （-gas）-water inversion, indicating that the oil （gas） accumulated under the water. However, the oil （gas） tends to accumulate over water in shallow reservoirs. Fourth, continuous unconventional tight hydrocarbon reservoirs are distributed widely in deep reservoirs, where the buoyancy force is not the primary dynamic force and the caprock is not involved during the process of hydrocarbon accumulation. Conversely, the majority of hydrocarbons in shallow regions accumulate in traps with complex structures. The results of this study indicate that two dynamic boundary conditions are primarily responsible for the above phenomena： a lower limit to the buoyancy force and the lower limit of hydrocarbon accumulation overall, corresponding to about 10%-12% porosity and irreducible water saturation of 100%, respectively. These two dynamic boundary conditions were used to divide sedimentary basins into three different dynamic fields of hydrocarbon accumulation： the free fluid dynamic field, limit fluid dynamic field, and restrain fluid dynamic field. The free fluid dynamic field is located between the surface and the lower limit of the buoyancy force, such that hydrocarbons in this field migrate and accumulate under the influence of, for example, the buoyancy force, pressure, hydrodynamic force, and capillary force. The hydrocarbon reservoirs formed are characterized as ＂four high,＂ indicating that they accumulate in high structures, are sealed in high locations, migrate into areas of high porosity, and are stored in reservoirs at high pressure. The basic features of distribution and accumulation in this case include hydrocarbon migration as a result of the buoyancy force and formation of a reservoir by a caprock. The limit fluid dynamic field is located between the lower limit of the buoyancy force and the lower limit of hydrocarbon accumulation overall; the hydrocarbon migrates and accumulates as a result of, for example, the molecular expansion force and the capillary force. The hydrocarbon reservoirs formed are characterized as ＂four low,＂ indicating that hydrocarbons accumulate in low structures, migrate into areas of low porosity, and accumulate in reservoirs with low pressure, and that oil（-gas）-water inversion occurs at low locations. Continuous hydrocarbon accumulation over a large area is a basic feature of this field. The restrain fluid dynamic field is located under the bottom of hydrocarbon accumulation, such that the entire pore space is filled with water. Hydrocarbons migrate as a result of the molecular diffusion force only. This field lacks many of the basic conditions required for formation of hydrocarbon reservoirs： there is no effective porosity, movable fluid, or hydrocarbon accumulation, and potential for hydrocarbon exploration is low. Many conventional hydrocarbon resources have been discovered and exploited in the free fluid dynamic field of shallow reservoirs, where exploration potential was previously considered to be low. Continuous unconventional tight hydrocarbon resources have been discovered in the limit fluid dynamic field of deep reservoirs; the exploration potential of this setting is thought to be tremendous, indicating that future exploration should be focused primarily in this direction.

Main progress and problems in research on Ordovician hydrocarbon accumulation in the Tarim Basin

The Tarim Basin is the largest petroliferous basin in the northwest of China, and is composed of a Paleozoic marine craton basin and a Meso-Cenozoic continental foreland basin. It is of great significance in exploration of Ordovician. In over 50 years of exploration, oil and gas totaling over 1.6 billion tonnes oil-equivalent has been discovered in the Ordovician carbonate formation. The accumulation mechanisms and distribution rules are quite complicated because of the burial depth more than 3,500 m, multi-source, and multi-stage accumulation, adjustment, reconstruction and re-enrichment in Ordovician. In this paper, we summarized four major advances in the hydrocarbon accumulation mechanisms of Ordovician carbonate reservoirs. First, oil came from Cambrian and Ordovician source rocks separately and as a mixture, while natural gas was mainly cracked gas generated from the Cambrian-Lower Ordovician crude oil. Second, most hydrocarbon migrated along unconformities and faults, with different directions in different regions. Third, hydrocarbon migration and accumulation had four periods： Caledonian, early Hercynian, late Hercynian and Himalayan, and the latter two were the most important for oil and gas exploration. Fourth, hydrocarbon accumulation and evolution can be generally divided into four stages： Caledonian （the period of hydrocarbon accumulation）, early Hercynian （the period of destruction）, late Hercynian （the period of hydrocarbon reconstruction and re-accumulation）, and Himalayan （the period of hydrocarbon adjustment and re-accumulation）. Source rocks （S）, combinations of reservoir-seal （C）, paleo-uplifts （M）, structure balance belt （B） matched in the same time （T） control the hydrocarbon accumulation and distribution in the Ordovician formations. Reservoir adjustment and reconstruction can be classified into two modes of physical adjustment and variation of chemical compositions and five mechanisms. These mechanisms are occurrence displacement, biodegradation, multi-source mixing, high-temperature cracking and late gas invasion. Late hydrocarbon accumulation effects controlled the distribution of current hydrocarbon. The T-BCMS model is a basic geological model to help understanding the control of reservoirs. At present, the main problems of hydrocarbon accumulation focus on two aspects, dynamic mechanisms of hydrocarbon accumulation and the quantitative models of oil-bearing in traps, which need further systemic research.

Fault characteristics and control on hydrocarbon accumulation of middle-shallow layers in the slope zone of Mahu sag, Junggar Basin, NW China

The development, evolution and formation mechanism of faults and their control on the migration and accumulation of Mesozoic oil and gas in the middle-shallow layers of the slope zone of Mahu sag were studied by the interpretation of seismic and drilling data. Two types of faults, normal and strike-slip, are developed in the middle-shallow layers of the slope zone of the Mahu sag and they are mostly active in the Yanshanian period. They are divided into four grade faults: The grade I strike-slip faults with NWW to near EW direction are related to the left-lateral transpressive fault zones in the northwest of Junggar Basin since the end of the Triassic. The grade II faults with NE to NNE direction are the normal faults located at the junction of the fault zone and the slope zone, and their formation is related to the extension at the top of the nose-like structures in the fault zone. The grade III faults, which are also the normal faults, are the result of the extension at the top of the lower uplifts in the slope zone and differential compaction. The grade IV faults with NE direction are normal faults, which may be related to the extension environment at the tip of the lower uplifts. Faults not only are the channel for the vertical migration of oil and gas, but also control the oil-gas accumulation. There are two types of oil-gas reservoirs in the middle-shallow layers of slope zone of Mahu sag: fault block reservoirs and fault-lithologic reservoirs. They have large traps and promising exploration potential.

Main Structural Styles and Deformation Mechanisms in the Northern Sichuan Basin,Southern China

The Triassic Jialingjiang Formation and Leikoupo Formation are characterized by thick salt layers. Three tectono-stratigraphic sequences can be identified according to detachment layers of Lower-Middle Triassic salt beds in the northern Sichuan Basin, i.e. the sub-salt sequence composed of Sinian to the Lower Triassic Feixianguan Formation, the salt sequence of the Lower Triassic Jialingjiang Formation and Mid-Triassic Leikoupou Formation, and the supra-salt sequence composed of continental clastics of the Upper-Triassic Xujiahe Formation, Jurassic and Cretaceous. A series of specific structural styles, such as intensively deformed belt of basement-involved imbricated thrust belt, basement-involved and salt-detached superimposed deformed belt, buried salt-related detached belt, duplex, piling triangle zone and pop-up, developed in the northern Sichuan Basin. The relatively thin salt beds, associated with the structural deformation of the northern Sichuan Basin, might act as a large decollement layer. The deformation mechanisms in the northern Sichuan Basin included regional compression and shortening, plastic flow and detachment, tectonic upwelling and erosion, gravitational sliding and spreading. The source rocks in the northern Sichuan Basin are strata underlying the salt layer, such as the Cambrian, Silurian and Permian. The structural deformation related to the Triassic salt controlled the styles of traps for hydrocarbon. The formation and development of hydrocarbon traps in the northern Sichuan Basin might have a bearing upon the Lower-Middle Triassic salt sequences which were favorable to the hydrocarbon accumulation and preservation. The salt layers in the Lower-Middle Triassic formed the main cap rocks and are favorable for the accumulation and preservation of hydrocarbon.

塔里木盆地台盆区走滑断裂带多层叠加样式及石油地质意义

随着塔里木盆地油气勘探的不断深入,在台盆区古生界发现大规模走滑断裂系统,提出了一种新型断溶体油气藏。受塔里木盆地多期构造运动的影响,走滑断裂表现出多层结构,具有多期叠加活动特征。基于高品质三维地震资料、钻井资料及油气地质资料,对塔里木盆地大型走滑断裂的多层叠加特征及对油气的控制作用展开研究。研究结果表明:塔里木盆地台盆区走滑断裂带在古生界主要发育5个结构层,分别为下寒武统盐下构造层、中寒武统盐构造层、上寒武统—中奥陶统碳酸盐岩构造层、上奥陶统—石炭系碎屑岩构造层和二叠系岩浆岩构造层;受多期构造运动及走滑断裂带活动的影响,5层结构在空间上具有带状分布、垂向叠置、差异叠加的特征;断裂叠加类型多样,总体上可以分为连接型、叠接型、反转叠加型及反转改造型4种;走滑断裂带叠加方式影响了石油地质条件,可形成多层差异聚集油气藏,主要包括Ⅰ型油气藏(奥陶系碳酸盐岩油气藏)、Ⅱ型油气藏(奥陶系碳酸盐岩油气藏、志留系碎屑岩油气藏及二叠系岩浆岩油气藏)及Ⅲ型油气藏(寒武系盐下层白云岩油气藏)3种类型。

全油气系统理论基本原理

通过阐释全油气系统基本原理,并阐明全油气系统的结构,进而揭示常规油气—致密油气—页岩油气序列成藏规律以及全油气系统成藏模式与成藏机理;此外,阐述了页岩油气-致密油气储层地质模型、流动模型与开发生产机理,并给出了进一步的研究方向。研究表明:(1)全油气系统的主要结构包括3类流体动力场、3种油气藏与油气资源,以及两种成藏作用。常规油气—致密油气—页岩油气具有形成时间和空间分布的有序性、基于成因机理的序列合理性,表现出“序列成藏”的地质规律。(2)全油气系统成藏模式可以分为“碎屑岩盆地成藏模式”与“碳酸盐岩盆地(层系)成藏模式”两类。非常规油气的聚集成藏是一种“自封闭成藏”,油气自封闭作用的微观来源是分子间作用力(范德华力)。(3)非常规油气生产实践证实,页岩油气-致密油气储层地质模型、流动模型与开发生产机理是一个全新的领域,极为复杂,有待进一步研究。页岩油气一定是中国油气资源中最重要的资源接替。(4)进一步研究方向包括:碳酸盐岩盆地全油气系统特征及复合盆地演化源储耦合规律;页岩油气与致密油气运移、成藏与开发生产的流动机理;深层超深层页岩油气、致密油气和煤层气油气地质特征与富集规律;全油气系统油气资源评价与新一代盆地模拟技术;地球系统—地球有机岩与化石能源系统—全油气系统研究。

深层—超深层海相碳酸盐岩成储成藏机理与油气藏开发方法研究进展

基于钻井、地震、测井、测试以及实验分析等新资料,针对中西部叠合盆地深层—超深层海相碳酸盐岩层系成储、成藏和油气藏高效开发面临的关键科学问题开展持续攻关。研究表明:(1)断裂主导形成的储集体和古老层系白云岩储层是深层—超深层海相碳酸盐岩两类重要的储层;以断裂为主导形成的规模储集体,根据成因可进一步分为3种类型:断裂活动过程中构造破裂形成的缝洞储集体、致密碳酸盐岩受断裂和流体双重改造形成的储集体与早期丘滩等高能相带受断裂和流体改造形成的储层;优势丘滩相、早期白云石化和溶蚀、酸性流体环境、膏盐岩封盖和超压是优质白云岩储层形成和保持的关键。(2)中国中西部叠合盆地海相碳酸盐岩层系富有机质页岩主要发育于被动陆缘深水陆棚、碳酸盐缓坡等环境中,构造-热体制是控制深层—超深层油气藏赋存相态的重要因素,改造型动力场控制中西部叠合盆地深层—超深层海相碳酸盐岩油气成藏与分布。(3)普光等高含硫酸性气田开发过程中硫析出堵塞井筒,采用井筒溶硫剂配合连续油管解硫堵效果明显;基于沉积模拟的双重介质建模数模一体化技术可以精细刻画水侵前缘空间展布及变化,并据此提出气井全生命周期调、排、堵控水对策。(4)超深断控缝洞油气藏开发过程中,储层应力敏感,渗透率随压力下降而显著降低,产量递减较快;凝析气藏相态变化快,压降显著影响凝析油采出程度;据此提出“注水+注天然气”重力驱油藏开发方法和“高注低采”天然气驱凝析气藏开发方法;采用分层次约束、逐级地质建模和流-固-热耦合的复合介质数值模拟有效提高了油气藏开发生产动态模拟的预测精度。

渤海湾盆地渤南低凸起西段低角度正断层分段生长特征及其油气地质意义

为了研究渤海湾盆地渤南低凸起低角度正断层分段生长诱发的时空差异演化特征及控藏机制,基于最新三维地震资料,精细刻画表征了断层分段生长过程及差异演化特征,结合区域构造背景,探讨断层成因机制及对油气成藏的控制作用。结果表明:渤南低凸起南边界F1断层和F2断层均为低角度正断层,源于中生代NWW—近EW向先存逆冲断层发生负反转,在新生代发生再次活化。F1断层具有平面上分段连接、垂向上多幕活动的特征,中段继承原有断面持续活动,西段和东段分别与裂陷Ⅱ幕新生NEE向断层和裂陷Ⅲ幕新生近EW向断层垂向搭接形成现今形态。低角度正断层对油气成藏的控制作用主要表现为:①低角度正断层断控侧沉积规模大,可提供充足的可容纳空间,形成规模陡坡砂体;②长期活动的低角度正断层是垂向油气运移通道,控制了油气垂向上的富集层位;③低角度正断层多期活动改造了深部储层物性,断层活动强度与优质储层的发育密切相关。

An isotope study of the accumulation mechanisms of high-sulfur gas from the Sichuan Basin, southwestern China

The mechanism of hydrogen sulfide(H_2S) generation plays a key role in the exploration and development of marine high-sulfur natural gas, of which the major targets are the composition and isotope characteristics of sulfur-containing compounds.Hydrocarbon source rocks, reservoir rocks, natural gases and water-soluble gases from Sichuan Basin have been analyzed with an online method for the content of H_2S and isotopic composition of different sulfur-containing compounds. The results of comparative analysis show that the sulfur-containing compounds in the source rocks are mainly formed by bacterial sulfate reduction(BSR), and the sulfur compounds in natural gas, water and reservoir are mainly formed by thermal sulfate reduction(TSR). Moreover, it has been shown that the isotopically reversion for methane and ethane in high sulfur content gas is caused by TSR. The sulfur isotopic composition of H_2S in natural gas is inherited from the gypsum or brine of the same or adjacent layer,indicating that the generation and accumulation of H_2S have the characteristics of either a self-generated source or a near-source.

渤海湾盆地黄骅坳陷古生界源内和源下油气成藏特征及有利区预测

煤系烃源岩是渤海湾盆地黄骅坳陷古生界含油气系统的主要烃源岩,源内和源下油气聚集机制和油气成藏过程不清。基于测井、录井、地震资料,结合烃源岩地球化学分析、储层岩心测试、包裹体测试、物理模拟实验等多种手段,探讨了渤海湾盆地黄骅坳陷古生界源内及源下油气聚集机制和成藏过程。研究结果表明:①黄骅坳陷古生界源内储层可有效聚集油气,紧邻的煤系地层烃源岩可优先对其供烃,稳定的构造背景使源内油气藏得到良好的保存。②研究区源下储层油气成藏的2个必要条件为:上部终止于煤系内部且下部连接奥陶系储层的断裂系统,且低角度断裂的油气输导效率更高;源储间存在大于10 MPa的压差,可为源下储层的油气成藏提供良好的动力。③研究区源内及源下油气藏具备早晚2期成藏、中期破坏的特征。中白垩世,低熟的煤系原油大量充注于储层中;白垩纪末期,地层的强烈抬升使古油藏遭受破坏或调整;新生代,随着烃源岩进一步成熟并生、排烃,形成了大量煤型气和轻质油油气藏。④研究区烃源岩有效充注范围内,储层相对优质、构造相对稳定的区域为源内勘探有利区,印支期逆冲断裂发育、受后期伸展作用改造较弱的区域为源下勘探有利区。

鄂尔多斯盆地延长组裂缝特征及其控藏作用

为确定断裂发育区油气充注聚集在时间上的持续性和在空间上的有序性,以鄂尔多斯盆地南缘上畛子—转角地区为例,分析裂缝形成期次与油藏分布的关系,探讨裂缝对延长组油藏的控制作用。研究表明,延长组主要发育燕山运动期二幕、燕山运动期三幕和喜马拉雅运动期共3期裂缝,不同期次裂缝对油气运聚的作用不同。近源油藏捕获了烃源岩从低熟到成熟阶段的所有产物,在燕山运动期三幕和喜马拉雅运动期遭到破坏,原油向远源区调整。研究区南部靠近渭北隆起,其裂缝的纵向连通性及砂体发育程度较强,原油在远源储集层中富集;研究区北部原油主要滞留在近源储集层中。因此,裂缝与砂体对接形成的输导网络,可以对油藏起到调整作用,在多期次裂缝的沟通下,近源和远源油藏的资源量立体互补。

油气盖层研究现状与认识进展

综述了油气盖层研究历史和国内外研究现状,分别总结了泥岩盖层及蒸发岩类盖层认识进展,分析了封盖机理研究现状。提出油气盖层研究经历了5个阶段,逐渐由早期侧重于盖层物性研究发展到变形过程及成藏过程中的盖层有效性研究,包括优质盖层研究、盖层力学性质研究以及盖层封盖性与成藏条件匹配关系研究等。蒸发岩类是世界各地重要的油气盖层,后期岩溶改造会对其封盖性能产生一定的影响;泥岩的沉积结构、构造、成分组成,特别是粘土含量对泥岩盖层封闭性能影响较大;深埋地下的高演化泥岩仍具有优质的封盖性能。尽管发现毛管物理封闭、超压封闭和毛管多相封闭等多种封闭类型,但是,毛管物理封闭作用是最基本的封闭机制。总体上,国际上目前研究盖层较多的国家主要有美国、挪威、澳大利亚、英国、意大利、德国等,研究单位包括高校、政府机构和油气公司等。

含油气盆地盐构造研究进展

简要讨论了近年来含油气盆地盐构造研究的主要进展,这些进展主要表现在盐构造地质建模、三维可视化、物理模拟和数值模拟、平衡剖面分析和构造复原以及盐构造形成机制等方面。盐构造是一类与油气聚集关系极为密切的构造类型,在波斯湾、北海、墨西哥湾、北欧和非洲大陆边缘等油气资源丰富的地区有大量分布。中国在塔里木、渤海湾、江汉、四川等盆地广泛发育多期盐岩层和多种类型的盐构造,但国内盐构造研究相对较少,对盐及其相关构造的变形组合样式、三维地质建模和三维可视化、盐构造形成机理和动力学演化的研究是薄弱环节。对于塔里木、渤海湾盆地以及中国南方海相碳酸盐岩层系来说,区域性盐岩盖层的存在和分布将是油气藏得以保存的关键。深入探讨盐构造特征将有助于深化对中国含油气盆地构造演化、构造样式和油气成藏过程的认识。

鄂尔多斯盆地延长组低渗透致密岩性油藏成藏机理

以层序地层学为指导,从成藏条件解剖入手,从孔隙演化的角度分析鄂尔多斯盆地中生界上三叠统延长组低渗透致密岩性油藏成藏机理,归纳其成藏演化模式。延长组低渗透致密岩性油藏分布于优质烃源岩范围内,湖相重力流沉积与三角洲前缘沉积为主要储集砂体类型。延长组低渗透致密砂岩在早期成藏期具有高孔高渗的特点,早期生成的油气在浮力作用下正常成藏,中后期成藏过程中经历了持续压实致密过程;后期主生烃期生成的原油在浮力和源储压差共同作用下沿先前残余路径以浸润方式运聚,达到致密条件时,油气停止运移。晚侏罗世—早白垩世中期,油气在高孔隙砂岩中近源多点面状充注大面积成藏,油气从湖盆中心向四周运移;早白垩世晚期,砂岩储集层成岩作用加强,储集层发生致密化。晚白垩世之后,受西倾东翘的构造挤压抬升运动影响,形成现今低渗透致密岩性油藏。

砂岩透镜体成藏机理

砂岩透镜体油藏是隐蔽油气藏中增储上产的重要类型 ,但目前对其成藏机理的认识还存在很大分歧 .从油气初次运移机理入手 ,结合砂泥岩压实成岩过程的分析 ,对砂岩透镜体的成藏动力和成藏阻力及成藏过程进行了分析 .研究认为 :烃类生成引起的膨胀力、烃浓度差引起的扩散力和砂泥岩间的毛管压力差是成藏主动力 ,岩石吸附和粘滞力是成藏主要阻力 ;油气水以混相涌流方式为主 ,孔隙、微裂隙和微层理面是油气运移的通道 ;早成岩阶段不成藏 ,晚成岩早期成藏 。

油气成藏及分布序列的连续聚集和非连续聚集

随着勘探的深入、科技的发展,诸如煤层气、页岩油气、根缘油气及水溶气等多种类型的油气藏逐步被勘探开发。按照聚集类型可将其划分为"源端元"及其附近的连续聚集和"储端元"及其附近的非连续聚集,分别形成非常规油气藏和常规油气藏,并包含了中间多种类型的过渡油气藏,兼或具有两种聚集特征。为此,在对油气成藏和分布序列研究的基础上,探讨了上述两种聚集类型形成的油气藏种类、分布和特征等,以期对油气藏分类和勘探决策提供参考。结论认为:非常规油气藏和常规油气藏在理想盆地成藏和分布上构成一个完整的序列,平面上从盆地中心向边缘、剖面上从深部向浅部依次形成煤层气藏、页岩油气藏、根缘油气藏、水溶气藏、常规油气藏等;在源储关系(静态因素)、运移特征(动态因素)及油气赋存状态上呈有规律的变化;伴随着构造、温压、生烃量、运聚、储集等地质条件的变化,连续聚集和非连续聚集的油气藏可以相互转化。

济阳坳陷古近系深层成烃与成藏

运用地球化学与沉积学、石油地质学相结合的方法,从深层烃源岩空间展布及沉积有机相分析入手,研究济阳坳陷深层有利勘探方向。济阳坳陷古近系深层孔店组—沙四段烃源岩发育缺氧有机相、短暂充氧有机相、低氧有机相和充氧有机相4种沉积有机相类型,缺氧相、短暂充氧相优质烃源岩主要发育在沙四段,孔店组烃源岩主要为低氧有机相、充氧有机相,为一般烃源岩。排烃过程可分为自由排水、烃类生成和能量积累及微裂隙排烃等3个阶段,深层烃源岩的排烃主要发生在微裂隙排烃阶段,不同地质条件下可发生垂向运移、侧向运移和向下运移3种油气运移方式。已探明中浅层源自沙四段缺氧有机相、短暂充氧有机相优质烃源岩的油气藏,主要通过沿断裂的垂向运移方式成藏,而大量以侧向运移及向下运移方式形成的油气藏尚有待于揭示。古近系深层仍具有较大的勘探潜力。

塔里木盆地克拉通内古隆起的成因机制与构造类型

古隆起是克拉通盆地的重要构造单元。由于盆地边界条件与深部构造背景的变化,古隆起的形成与发育表现为复杂的动力学过程。借助于地震反射剖面与钻探资料,可以刻画不同地质时期古隆起的分布、形态、结构与构造样式,剖析古隆起的成因机制。文中以塔里木盆地为例,对古生代克拉通内古隆起的几何学与运动学特点进行描述,结合周缘大地构造背景的演变,剖析了古隆起的形成机制。在此基础上,将克拉通内古隆起划分为稳定型、活动型、残余型与消亡型4种基本类型。由于运动体制的变革,古隆起经历了形成发育、叠加改造、调整定型与最终埋藏的动力学演变,具有多层叠加的地质结构,并发育断裂带、背斜带、地层剥蚀尖灭带等一系列构造带。古隆起是油气聚集的主要单元,古隆起的动力学演化历史决定了隆起富集油气的关键条件。