Study On Source Rock And Reservoir Forming Dynamic Of Chang 7-member In Qilicun Oilfield,Ordos Basin

The quality of source rock and oil-source correlation in the margin of chang7 lake basin of Ordos Basin has been hot topics of debate.In the past,people thought that there was no effective source rock in this area.The crude was generated by the source rock in the center of chang7 lake basin and migrated from the center of chang 7 lake basin to this area with a long distance lateral migration.In this paper,core observation,geochemical test analysis and well logging evaluation of source rock were used to carry on the comprehensive evaluation of source rocks and oil-source correlation in this area.In addition,due to the low degree of research on reservoir forming dynamics in this area.Comprehensive analysis was used to determine the origin of paleo overpressure,Based on the study of the characteristics of reservoir fluid inclusions petrographic and microscopic temperature measurement,this study uses the state equation combined with the basin simulation method to restore the paleo-pressure and pressure evolution history of reservoir and source rock formation,and determines the pressure state of oil main charging into the reservoir period.The distribution area of chang7 source rock in Qilicun oilfield is large.The source rock could be divided into black mud shale and dark mudstone,with average thickness of 9.2m and 28.9m respectively.Chang7 source rock has high organic matter abundance.The average TOC of Black mud shale is 2.73%,which can accord with the "best" source rock standard and dark mudstone is 1.98%,which can accord with the "medium good" source rock standard.The type of organic matter of Chang7 source rock is ???1.The Ro is distributed between 0.67%and 0.76%,with an average of 0.71%.The Tmax is 450? on average.These all indicate that the source rock has reached maturity and entered into a large amount of oil generation stage.The geochemical characteristics and the result of oil-source correlation of source rock showed that the Chang 6 crude oil in Qilicun oilfield was mainly from the local Chang 7 source rock,without a long distance lateral migration.The fluid inclusions in Chang 6 reservoir are mainly developed in quartz grain microcracks and calcite cement,and the hydrocarbon inclusions are abundant The homogenization temperature is concentrated between 110?125 ?,and the accumulation time is about 120Ma?100Ma,corresponding to the end of Early Cretaceous.The formation is in negative pressure at present.There was paleo overpressure in reservoir forming period and the genesis mechanism of overpressure is mainly hydrocarbon generation.The paleo pressure value in reservoir was between 27.3?34.OMPa.The hydrocarbon generation pressure value of Chang7 source rock ranges from 17.2MPa to 22MPa.The overpressure in the source rock is the main driving force for crude oil to flow out of the source rock and into the reservoir.The hydrocarbon generation and expulsion history,overpressure evolution history and hydrocarbon accumulation history of source rock have good coupling.The distribution and filling degree of the reservoir are controlled by the source rock of Chang 7 and reservoir forming power in Qilicun oilfield.