Reservoir-forming Structural Combination And Reservoir Distribution Of Yanchang Formation And Yan'an Formation Reservoirs In Ordos Basin

The Mesozoic Yanchang Formation in Ordos Basin is a hot spot for exploration and development of tight reservoirs in China.With further of exploration and development,more and more attention has been paid to the influence of structure on the formation and distribution of tight reservoirs.Although predecessors have done a lot of research on Mesozoic regional structures,area structures,trap structures,etc.The study of structures(Concave-uplift combination structure,Fault)closely related to hydrocarbon accumulation is not deep enough.According to the combination of slot line,Valley line,ridge line and uplift line,to analyze the structural characteristics of the Chang 7 bottom's present concave-uplift combination,Yanchang Formation bottom's early cretaceous epoch paleo-concave-uplift combination and Yanchang Formation bottom's late cretaceous epoch-neogene period.And the superposition relationship of paleo-present concave-uplift combination structures is also analyzed.Using twodimensional seismic data to further calibrate the faults that determined by remote sensing,surface data and gravity and magnetic data in Chang 7 source rock range,the plane and the section plane characteristics of the faults are also studied.Finally,discussing the relationship between reservoir-forming structural combinations and discovered reservoirs,to get the following main understandings:(1)Chang 7 botton's present concave-uplift combination structure,Yanchang Formation bottom's early cretaceous epoch paleo-concave-uplift combination structure and Yanchang Formation bottom's late cretaceous epoch-neogene period paleo-concave-uplift combination structure can be divided into three types that include point concave-side uplift combination structure,side concave-side uplift combination structure and side concave-middle uplift combination structure.And according to the superposition relations between Chang 7 botton's present concave-uplift combination structure,Yanchang Formation bottom's early cretaceous epoch paleo-concave-uplift combination structure and Yanchang Formation bottom's late cretaceous epoch-neogene period paleo-concave-uplift combination structure to divided into three area that include paleo-present accordance area,paleo-present approximate difference area and paleo-present opposite difference area.(2)Using two-dimensional seismic data to further calibrate and confirm 26 large faults developed in Chang 7 source rocks reign,and preliminarily analyzing the faults characteristics.According to the relationship between the strike of faults and the strike of strata to classify two types that include along-slope faults and cut-slope faults.And there almost are slope faults in the basin.According to the stratum where was broken to classify the fault-to-surface type and the fault-to-surface type.(3)The Chang 6 tight sandstone reservoirs discovered in the Yanchang Formation are mainly distributed in the middle-high parts of Chang 7 botton's present concave-uplift combination structure,Yanchang Formation bottom's early cretaceous epoch paleo-concave-uplift combination structure and Yanchang Formation bottom's late cretaceous epoch-neogene period paleo-concave-uplift combination structure,and mainly in the paleo-present concave-uplift combination structure accordance area,and the Chang 6 reservoir is also distributed outside the scope of hydrocarbon source rocks.And the Yanchang Formation Chang 10-Chang 8,Chang 4+5-Chang 1,Yan'an Formation sandstone reservoirs and Chang 7 shale reservoirs are mostly distributed near faults.(4)The hydrocarbon accumulation and distribution of the discovered Chang 6 and Chang 7 tight sandstones are obviously influenced by the paleo-present concave-uplift combination structure accordance area,Therefore,in the exploration and development of these strata,based on the study of sand body,we should pay attention to the influence of concave-uplift combination structure on hydrocarbon accumulation and reservoir characteristics.The reservoir formation and distribution of Chang 10-Chang 8,Chang 4+5-Chang 1,Yan'an sandstone oil and gas and Chang 7 shale oil and gas are obviously affected by faults.Therefore,the influence of faults on reservoir formation and reservoir characteristics should be considered when exploring and developing these formations.