Oil Accumulation In Deep Layers Of Yanchang Formationunder The Control Of Formation Pressure,Ordos Basin

The deep layers of the Yanchang Formation in the Ordos Basin have now become the main stratum for exploration and development and have made some progress.Although it is recognized that formation pressure is the main factor controlling the distribution of oil and gas,the specific distribution of formation pressure and the distribution of oil and gas under its control are still unclear.The lack of corresponding research on the situation has become a key problem in further dividing favorable areas and hindering the development of oil and gas fields,which needs to be solved urgently.The sedimentary facies and sand body distribution characteristics of the Chang 7-Chang 9sublayers in the study area were analyzed by comprehensive application of logging,logging and other data.Accurately calculate the specific residual pressure value of each sublayer and its distribution characteristics on the profile and plane,and analyze the plane distribution position of each sublayer reservoir in combination with the production test data and analyze its accumulation and distribution law in combination with the above research.The research shows that the Chang 7-Chang 9 strata in the study area are dominated by shallow water delta sediments,the northeast direction sand bodies are mainly channel direction,distributed in strips,and the thickness of the sand bodies is relatively large.7turbidite fan sand bodies are also relatively developed;from the plane,the residual pressure of Chang 7 formation generally develops a high value of more than 15Mpa,the residual pressure value in most areas of Chang 8₁is between 0 and 5Mpa,and the residual pressure value of Chang 8₂is distributed with high value.Similar to Chang 8₁,the high value of residual pressure in Chang 9₁is distributed in a NW-trending belt,and most of the remaining areas are below 10Mpa,while the change in residual pressure in Chang 9₂is relatively gentle,mostly around 5Mpa.Longitudinal view of Chang 7 and Chang 9₁strata The residual pressure value is relatively high,showing the characteristics of high in the south and low in the north,high in the west and low in the east;on the plane,the sand bodies in the dominant sedimentary facies belt of the Yanchang Formation,the distribution near the source,and the relatively low-value area near the high-value area of residual pressure in the small layer are oil and gas migration.The favorable accumulation areas that have been moved,the longitudinally dominant sedimentary sand bodies and the areas with high residual pressure difference between source and reservoir are favorable oil and gas accumulation areas.This study provides theoretical guidance for tight oil exploration.