The chemical compositions of 20 crude oils and the extracts of potential source rocks from the Jinhu Depression of the North Jiangsu-South Yellow Sea Basin, eastern China were studied in detail by geochemical methods in order to understand their genetic relationship. The oil samples were collected from the major producing fields in the Western Slope (WS) and the Biandong-Yangjiaba-Minqiao uplift belt (BMY). The rock samples studied, selected after Rock-Eval pyrolysis screening of a large suite of samples, consist of 20 shale samples in the E2f2 member of the Paleocene Funing Formation from the oilfield areas (WS and BMY) and the Sanhe sag all within the Jinhu Depression. Geochemical characteristics indicate only one single family of oils. A number of biomarker features support deposition of the source rocks for these oils under conditions of enhanced salinity/stratified water columns. A wide thermal maturity range for the oils as indicated by sterane isomerization ratios was not substantiated by other maturity parameters. The genetic relationships between the oils and the E2f2 member of the Paleocene Funing Formation present in the deeper parts of the Sanhe and Longgang sags were suggested using a wide range of molecular parameters. Variation in the sterane concentrations in source rocks with different maturity suggests that migrational contamination and/or in-situ extractions of organic matter from caprocks or intra-reservoir shales by mature oils could potentially produce oils with apparent immaturity at the molecular level. Secondary alteration (e.g. biodegradation) of oils in the reservoir could also have a similar effect on the bulk oil compositions. Although we do not discount the possible presence of minor amounts of "immature oils", exploration focus in the Jinhu Depression, as well as many other rift basins in eastern China, should be on mature oils derived from the deep source kitchens.

根据油气运聚的动力和作用方式将油气藏成因分为3类8种17式。这8种分别是：①高压势场作用下形成的油气藏；②低压势场作用下形成的油气藏；③由水携带溶解气游离释放形成的天然气藏；④浮力作用下形成的油气藏；⑤毛细管力作用下形成的油气藏；⑥天然气体积膨胀形成的深盆气藏；⑦分子吸附作用形成的煤层瓦斯气藏；⑧分子水合作用形成的水合甲烷气藏。①～③种为突发式流压作用形成的油气藏，④～⑥种为缓慢式烃势差形成的油气藏，⑦和⑧为非常规条件下天然气汇聚形成的特殊类型的（油）气藏。相同动力学成因的油气藏因实际地质条件的差异可以进一步分成亚类。不同动力学成因的油气藏的分布规律、主控因素和产状特征不同。研究油气运聚的动力机制和成因模式对指导油气田勘探提高勘探效益具有重要意义。

The mature oil/gas source rocks exist mainly in Jurassic strata in the northwest and in Tertiary strata in the west of Qaidam Basin. Oil and gas generated from the mature hydrocarbon source rocks in the Jurassic and Tertiary mainly accumulate in Tertiary formations in the Qaidam Basin. The main sedimentary facies in Tertiary formations include alluvial plain, lakeshore, shallow lake, semi-deep lake, alluvial fans, fan delta and sublacustrine fan. However, there were no fluvial facies. Most of the alluvial plain facies and lakeshore facies are very narrow and they become wide only where basin-bounding faults are present. Most parts of the basin are filled with shallow lake sediments such as pelitic siltstone and silty sandstone. The deposition systems have determined the hydrocarbon migration and accumulation patterns in Tertiary formations in different parts of the basin. In the inner basin where continuous permeable formations are absent, faults and fractures are the main pathways. Fractured rocks are the main reservoir types. Along the basin margins where continuous permeable formations occur in abundance, faults and fractures are also the main pathways. Therefore, the faults and fractures are very important for the hydrocarbon migration and accumulation. Four migration and accumulation models have been developed based on this study: (1) Migration and accumulation model through thrust faults. This model is mainly for migration and accumulation at the basin margin. The mudrock associated with the major fault is about 10 m thick so that there exist the hanging wall and footwall migration and accumulation zones. Where the major fault extends into source rocks areas, hydrocarbon migrated to and accumulated in the reservoir in the hanging wall. Otherwise, the faults just seal the reservoir in the footwall. (2) Migration and accumulation model through combined syn-depositional reverse faults and strike-slip faults. This model is also mainly for migration and accumulation at basin margins in which the strike-slip faults control different kinds of sedimentary fans and connections with hydrocarbon source areas; they are very suitable for hydrocarbon accumulation. (3) Migration and accumulation model through recoil faults. This model is mainly for migration and accumulation in fractured reservoirs in the inner basin region. (4) Migration and accumulation model through superficial thrust fault and lower strike-slip fault complex. This is mainly for migration and accumulation in the north of Qaidam Basin where the reservoirs are at the footwall of the superficial thrust faults.

油气在生排运聚成藏过程中须经历生烃排烃、运烃、聚烃和资源等5个门限。某一确定的油气运聚成藏系统进入任一个门限都将损耗一部分烃量。在实际地质条件下，源岩生成的烃量只有超过进入各个门限时损耗烃量之和才能大规模聚集成藏，并构成油气勘探的远景区。根据物质平衡原理研究油气生成量和损耗量之间的平衡关系，建立了相应的地质模型。在此基础上，提出了门限控烃作用及其计算模型。文中阐明了各门限的地质含义、判别标准及其控油气作用机理，给出了应用实例。

采用地质与地球化学原理与方法对渤海湾盆地八面河油气区进行系统测试和分析，定量估算该油田的油源分配，提出了相应的运移通道和成藏机理。研究结果表明，虽然八面河油田附近埋藏较浅的沙四段烃源岩提供的“未熟-低熟油”在八面河地区原油中占一定的比例，但这些原油的主体应来自相邻的生油洼陷--牛庄和广利洼陷内埋深超过2700m的沙四段成熟烃源岩。定量计算表明，八面河地区未熟-低熟油的含量不超过20%，其余为正常原油。来自生烃洼陷的油气的运移受断层、砂体运载层等优势通道共同控制，八面河油田只是运移优势通道的指向之一。新提出的原油来源与运聚模式已为近期油气勘探实践所证实。

The chemical compositions of 28 representative crude oils and oil sand samples collected from the Bamianhe region of the Bohai Bay Basin, eastern China were studied in detail in order to understand their genetic relationships, biodegradation ranking and thermal maturity level. Molecular geochemical parameters indicate the presence of one single oil family in the Cenozoic reservoirs. A number of biomarker features support deposition of the source rocks for these oils under conditions of enhanced salinity/stratified water columns. The extremely low maturity levels of these "immature oils", as indicated by sterane isomerization ratios, were not supported by other maturity parameters. The genetic relationship between the oils and the Es4 and Es3 members of the Eocene-Oligocene Shahejie Formation present in the deeper part of the Niuzhuang Sag, but not those along the Niuzhuang South Slope was suggested using a wide range of molecular parameters. Variation in the sterane concentrations observed from potential source rocks with different maturity levels in the study area suggests a high probability of migration contamination of mature oils by immature bitumens along migration pathways or from intra-reservoir shales. Variation in the level of oil biodegradation could also create anomalies in the use of gross oil compositions as an indicator of oil maturity. Although the recent rapid subsidence of the Bohai Bay Basin and the saline depositional environment of one of the potential source rocks favor oil generation at relatively low maturity levels, most of the economic oils discovered in the Bamianhe region appear to have derived from conventionally mature source rocks but contain lower maturity fluids admixed with them.

Hydrocarbn explusion threshold (HET) is the critical condition for hydrocarbon expulsion in separate phase from a source rock when the generated hydrocarbon amount has satisfied all needs for ahsorpBon by minerals, solution in water, and blocking of capillary pressure. Research results show that the HET varies mainly with three geological parameters: total organic carbon content (C%), kerogen type index (KTI) and thermal maturation degree (R0). Source rocks with low C% and KTI cross the HET at a high level of maturation degree (larger R0); source rocks with lower R0 and C% can also cross the HET if the kerogen has a larger KTI. Under general geological conditions, a source rock first crosses the methane expulsion threshold (HETgl), then the heavw hydrocarbon gas threshold (HETgn), and finally the liquid hydrocarbon expulsion threshold (HET0). In this paper the concept of HET, and its critical conditions, are applied to establish the scientific validity of the concept and grade the source rocks, to study the phases of hydrocarbons in migration and the mechanisms of hydrocarbon acvumulation, and to divide the hydrocarbon expulsion into stages. Applications to different basins in China show that HET provides an accurate and efficient method to guide oil and gas prospecting.