The Research Of Tight Oil Accumulationg Mechanisms Of Change 6 And Chang 7 Member In The North Zhifang-Shunning Oil Region

Including the abundant materials of loggings,laboratory analyses,petrolum testing,drilling data,experimental analysis,comprehensively using the reservoir geology,principles and methods of Sedimentology,the latestacademic theory of the petroleum geology,geochemistry,Hydrocarbon accumulation and reservoir-forming dynamics,etc,this article considers the “hydrocarbon generation”,“migration”and “accumulation” of Chang 6 and Chang 7 formation of Triassic Yanchang Formation in the north Zhifang-shunning,and finally we reached the following main understanding:(1)The sedimentary environment of Chang 6 oil-bearing formation and Chang 71 sandstone formation is the delta front subfacies,and the depositional environment of the Chang 72 sandstone formation is semi-deep lake deep lake subfacies.The Chang 6 and Chang 7 reservoir are tight reservoir,which is mainly composed of feldspathic sandstone,and the pore structure is complex.The physical property of the length of Chang 6 is better than that of Chang 7.(2)In the study area,the thickness of the hydrocarbon source rock of Chang 7 is mainly 30-45 m,the total content of organic carbon is relatively high,and the hydrocarbon generating intensity is about 157.7×104 t/km2.Inclusion can determinate hydrocarbon accumulation period and age in the study area.During the process of hydrocarbon generation,hydrocarbon generation-pressurization causes abnormal pressure,which provides the driving force for the primary migration of oil and gas.And abnormal pressure also causes the source rock to produce micro fractures,which provides the migration channel for the primary migration of oil and gas.(3)The reservoir types of Chang 6 and Chang 7 are mainly tight lithologic reservoirs,which are wide-distributed quadi-continuous accumulation in the reservoir stratum and Unconventional reservoir which is large area continuous distribution in the plane.The distribution of oil and water is not obvious,and there is no obvious oil-water interface.So the Chang 6 and Chang 7 reservoir are typical tight reservoir.The interior of the Chang 7 source rock is shale oil,which belongs to the formation of authigenic reservoir.The oil out of Chang 7 source rock,which is near the chang 6 and chang 7source rock,is belong to quadi-continuous tight oil.