Study On The Dynamics Of Petroleum Accumulation In Relict Basin Of Tertiary

To solving some main problems of the theory and method of dynamic Systems of Petroleum Accumulation in relict basin of Tertiary, the author takes Baise basin in Guangxi as an example. The basic characteristics of dynamic systems of petroleum accumulation are systemically studied in this paper by the using of the method of modern organic geochemistry and basin simulation with new technology of simulation experiment for migration and accumulation, which based on the comprehensive study of petroleum geologic condition in Baise basin with the material of regional geology.The characteristics of geochemistry on source rock and crude oil of different area in relict basin of Tertiary in Baise basin are systematic analyzed and the genetic type of oil have been classified by means of organic geochemistry. Moreover, based on the oil—oil and oil—rock correlation of biomarker, it is pointed out that the surveyed crude oil is originated from lake-facies dark mudstones in Nadu formation, while coal and carbonaceous mudstones have rather less contribution. It is determined that oil-source from west area is different from east area in basin, the crude oil of east depression is mainly from the second and first members of Nadu formation and the one of west depression is from the third members of Nadu formation.The hydrocarbon-generating characteristics of immature samples about main source rock in basin are systemically studied through thermal simulation experiment under continual heating. According to the systematic analysis of product of gas and liquid hydrocarbon, the hydrocarbon-generating model of organic about main source rock in basin is established for the first time. Based on the geologic condition, it points out that the organic of source rock in Nadu formation have the hydrocarbon-generating characteristics at low maturity or maturity stage, and especially have a strong hydrocarbon-generating capability at low maturity stage.The author analyzed the mechanisms of controlling formation on abnomal subpressure in a systematic way and put forward to the formation of abnomal subpressure which is the result of limited-entry and pressure drops based on the characteristics of modern geothermal, fluid pressure field and hydrochemical field. Take the reservoir of Nadu formation in East depression as a example, the author indicated that the formation of reservoir which is non-gas cap abnomal subpressure not only gets something to do with function of reflection about uplift and erosion of late strata, but also to do with limited sand body which loses the function of hydrostatic pressure with the ground water.According to the systematic analysis of the simulation experimente about migration and accumulation,it is discovered that the reservoir properties of sands conduit systems, the association pattern of sand body and fault and entering the oil poor which is from source rock to liquid conduit systems play a significant role to the reservoir-generating pattern of migration and accumulation. In the heterogeneous sand conduit systems, when the hydrocarbon which is from source rock entered the reservoir, it enters the heterogeneous sand body which permeability and porosity is rather high at first, and then enter the one which reservoir properties is poor with the increase density of entering the oil poor. Among the different association pattern of sand body and faults, oil conduit web formed by sands and heterogeneous sand leads to the complexity and variety of migration and accumulation.