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 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.

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.

Geological analysis and physical analogy exponments indicate that, under geological conditions, hydrocarbon tends to migrate along a path of least resistance and attempt to follow the largest buoyancy component There are four generalized modes of possible transport. First. hydrocarbons rends to migrate along the pathways with high porosity and permeability, and with a large grade difference relative to surrounding rocks (grade difference predominance): second, hydrocarbons rends to migrate in the opposite direction in oxverlying formations to the nadir of the sedimentation centre (divided syncline predominance): third. hydrocarbons tends to migrante in the direction of lower fluid pressure (fluid pressure predominance); fourth, hydrocarbons tends to migrate in the direction vertical to buoyancy (flow direction predominance). This paper reports on field observations in the Daqing oilfield area of China and also on physical analog experiments used to illuminate the four basic modes of transport Under geological conditions, the hydrocarbon migration pathways are controlled by these four basic modes, which can he used to predict the directions of hydrocarbons migration and select favourable exploration locations.

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.