| With the development of oil and gas exploration in the lower part of Yanchang Formation in Ordos Basin,high-yield oil and gas areas have been discovered in Chang 10 oil-bearing formation in the Zhoujiawan-Gaoqiao area,making the area to be the focus of exploration in Changqing Oilfield.However,the level of research on the formation of the 10 reservoir is relatively low,and seriously puts restriction on the process of exploration.Through logging,mercury injection,thin section and core observation,as well as horizontal and vertical section and plane and characteristics of the sandstone,we have identified the distribution of Chang1011 sandstone reservoir and the basic characteristics of reservoir.And on this basis,using the analysis method of organic carbon in rock pyrolysis,vitrinite reflectance and GC-MS,in combination with the theory of hydrocarbon accumulation,we have a clear understanding of the distribution and the charcteristics of source rocks(Chang7 and Chang9),the source of crude oil in different areas of Chang 1011 oil reservoir,dynamics and transporting system,build reservoir model,and summarize the pattern of hydrocarbon enrichment.The research of the distribution of sand body and the reservoir characteristics shows that Chang 1011 reservoir in Zhoujiawan-Gaoqiao area is mainly characterized by the sand bodies in the distributary channel of delta plain,with better connectivity and thickness along sand bodies,in comparison with those perpendicular to the source direction in the form of lenticles;the property of reservoir is low both porosity and permeability,among which the porosity is mainly distributed in more than 10%;the range of permeability more than1.4×10-3?m2,and dominated by intergranular pore and dissolved pore,plastic,high debris,medium content size,good sorting,denudation.The research shows that the mudstones in both Chang 7 and Chang 9 formations,full of high abundance of organic matter and good type of organic matter,have reached the mature stage;mudstones in both Chang 7 and Chang 9 formations develop and reach a certain scale in the whole area mudstone;thickness of Chang 7 in the west is larger and distribute in large expanse;mudstone thickness of Chang 9 in the east is thicker than that in the west.compared with geochemical parameters of Chang 7 and Chang 9 source rocks and crude oil,we optimize the distinct Ts and C30 Diahopane and C30 hopanes as parameters of oil source and then compare the correlation of different regions of the crude oil and source rock in the study area.The results show that the crude oil in a part comes from overlying source rocks in Chang 9 in the east part of 1011 of the study area,the other coming from the migration of source rocks of Chang 7 from west to east in the study area;the oil in Wuqi area is from source rock in overlaying Chang 7.with the dynamics generated by the undercompaction and abnormal high pressure of thick mudstone,the crude oil cuts through thick sand bodies along high angle fractures,and reserves in relatively high porosity and permeability.Lithologic reservoir and structural lithologic oil and gas reservoirs almost develop in Wuqi-Zhidan area.The accumulation of oil and gas is determined by many factors,including the transport system,the sand body,the physical property of the reservoir and the low amplitude structure.The oil in the whole area is mainly enriched in the low amplitude tectonic zone and the sand body with better porosity and permeability. |
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