Transition Of The Mesozoic-Cenozoic Tectonic Regimes And Hydrocarbon Accumulation In Western Ordos Region

Western Ordos region and its adjacent area is the geological & geophysical divide or transform hinge between circum-Pacific tectonic domain in eastern China and Tethyan tectonic domain in western China. Due to its particular tectonic location, this area had undergone multi-phase Compound and superimpose and single-phase combinate and restrict of different tectonic domain of Indosinian, Yanshanian and Himalayan from Mesozoic-Cenozoic, then develop a complex structural pattern and unbalanced petroleum geological conditions and hydrocarbon accumulation conditions. Then till today the exploration activity has not got a satisfied result because there have a good deal of uncertain factor in the Objective evaluation of Petroleum prospect controlled by the complicated geology conditions. So, based on the intensive study of the transition of the Mesozoic-Cenozoic tectonic regimes and hydrocarbon accumulation in western Ordos Region, the dynamic process of multi-phase basin formation and modification of the Mesozoic-Cenozoic in Western Ordos region and its adjacent area can be confirmed, the relationship between the generation, migration, accumulation and preservation of hydrocarbon and tectonic action and its superimpose can be understood, petroleum exploration targets can be evaluated objectively through a dynamic view. Then the results of the research provide the geologic basis for selection of petroleum exploration targets.Guide by the principles of sedimentary basin dynamics, by means of tectono-depositional analysis, combining surface and subsurface geologic analysis, geophysical and geochemical techniques along with testing data the structural characteristics of the Mesozoic-Cenozoic, prototype basin of different tectonic cycle, the relationship between transition of the Mesozoic-Cenozoic tectono-stress field and hydrocarbon accumulation in western Ordos Region and its adjacent area has been studied through the view of dynamic process of multi-phase basin formation and modification.The study of the tectonic feature of the Mesozoic-Cenozoic showed that the Mesozoic-Cenozoic in western Ordos Region and its adjacent area can be subdivided Indosinian, Yanshanian and Himalayan tectonic sequences. The contact relationship of parallel unconformity or lower angular unconformity between Indosinian and Yanshanian tectonic sequences showed that the tectonic deformation of Indosinian is scarcely notable. Based on the tectonic deformation of Yanshanian tectonic sequences, the structure of Yanshanian can be subdivided into three units, Bayanhaote-liupanshan palaeohigh, Wuhai-Pingliang palaeoanticlinorium tectonic zone, Tianhuan palaeosyncline. Based on the tectonic deformation of Himalayan tectonic sequences, the structure of Himalayan can be subdivided into five units, Hetao-Yinchuan extensional tectonic system, Shigouyi-Pingliang transform tectonic system, Liupanshan thrust-fault tectonic system.The study of prototype basin of different tectonic cycle showed that the basin of the Mesozoic-Cenozoic has evolved in different regimes in the western Ordos region and its adjacent area, which include the western part of great northern-Chinese cratonic basin from late Permian to early-middle Triassic, crooked-downwarp within compressional craton during late Triassic, the western part of depression basin within great Ordos craton during early-middle Jurassic, crooked-downwarp within compressional craton during middle-late Jurassic, piedmont depression controlled by thrust fault during late Jurassic and differential settlement under extension during early Crataceous.The study of the relationship between transition of the Mesozoic-Cenozoic tectono-stress field and hydrocarbon accumulation showed that there have superior source-reservoir-cap rock combinations in the western Ordos region. Its adjacent area and the tectonic activities which is mainly in inherited compressional regime controlled by the Mesozoic-Cenozoic tectono-stress field is the key element for the hydrocarbon accumulation.