Further recognition of the oil and gas accumulation conditions of Qingdong sag

WANG Yongshi; YANG Guili; ZHANG Shun

Abstract：Based on the new situation of oil and gas exploration in Qingdong sag,a combination of research methods for geological,geochemical and logging data analysis as well as 3D seismic fine interpretation were used to study the basic conditions for oil and gas accumulation in the study area.Key geological factors were realigned,and hydrocarbon accumulation models were also established.Qingdong sag is a typical Cenozoic shear extensional basin,develops three types of structural styles,the Es4s source rocks hydrocarbon generate and discharge early,complicated geological condition form models of oil-gas pool.The results show that the basin is controlled by the strike-slip Tancheng-Lujiang fault zone.The development of near EN,NWNWW and NNE trend fault zones forms a structural framework characterized by the juxtaposition of uplifted and depressional units with faulting in east and overlap in west.The tectonic style is dominated by stretch,stretch and strike-slip structure.The inversion tectonic style only develops locally.The conversion ratio of Es4s hydrocarbon source rocks changes rapidly between 2 500 m and 3 500 m.The range of hydrocarbon generation is relatively concentrated and the reservoir has great potential for hydrocarbon generation.Along the SN direction,structual and lithologic oil-gas pools distribute alternatively,while along the EW direction,strata,structural formation,structural-lithologic,lithologic and structural oil-gas reservoirs distribute in order.The hydrocarbon accumulation modes include multiple slope migration-accumulation,uplift in depression near-source migration-accumulation,slope belt fault strike migration-accumulation and in-situ accumulation within the sag.