Study On Characteristics Of Pressure Structure And Its Relationship With Hydrocarbon Distribution In The Zhanhua Depression

In order to reveal the essential relationship between overpressure structure and hydrocarbon distribution,taking Zhanhua Depression as an example,comprehensively unitizing geological,geophysical,analytical and test data,based on the detailed prediction of overpressure in Zhanhua Depression,the types of pressure structure are divided,genetic mechanism of pressure structure is analyzed,and the essential effect of pressure structure on oil and gas distribution is clarified combined with the oil and gas differential distribution.The results show that overpressure develops in Es1,Es3 and Es4 vertically.Pressure structure can be divided into abrupt and general type based on the pressure transition zone.Besides,pressure structure can be divided into funnel,complex funnel,bell and hill type,developed in Es1,Es3 and Es4,relatively.Overpressure structure genetic mechanism is complex,which is closely related to disequilibrium compaction,hydrocarbon generation,fluid release and burial depth.Funnel type is generated by disequilibrium compaction with a well seal,causing overpressure fluids easy to flow downward.Hill and bell type of Es3 are influence by source rock thermal maturation.Overpressure fractures are developed in the seal of bell type and hill type with high amplitude.The sand body acts as a fluid release pathway for hill shape with low amplitude.Overpressure body of Es4 is dominated by hydrocarbon generation.Complex funnel shape pressure structure is sealed by gypsum of no fracture.However,hill type is sealed by mudstone or gypsum with fractures.Hydrocarbon controlled by pressure structure is different.Hydrocarbon distributes in the bottom boundary and lower part of the overpressure body due to well sealing property and less hydrocarbon generation of funnel-shape pressure structure.The complex funnel-shape pressure structure is dominated by strong hydrocarbon generation and well sealing capacity,and oil and gas accumulate in reservoirs beneath the seal.However,the seals of hill-shape and bell-shape overpressure body are of poor sealing capacity,as a result,hydrocarbon mainly migrates upward and accumulate within the seal.