Paleozoic Tectono-Depositional Evolution And Petroleum System In Western Ordos Region

Western Ordos region and its adjacent area has undergone multi-phase intra-continental orogenic and basin-forming processes to develop an intracontinental tectonic complex as a 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 complex is characterized by variable stratigraphy, diverse structural grains, various depositional patterns as well as abundant ore deposits. As a result, a comprehensive research on the stratigraphic sequence, tectonic and depositional features, basin evolution is critical to better understanding the geodynamics of the Ordos Basin and to solving some key geological issues related to hydrocarbon exploration in the region. The results of the research provide the geologic basis for integrated evaluation and selection of Paleozoic natural gas prospects.Using the principles of continental dynamics and based on regional geologicl research , surface and subsurface geologic analysis, geophysical and geochemical techniques along with testing data analysis are available to analyse the structural style, the structural sequence and tectonic divsion. At last ,basin prototype and evolutional processes of petroleum system in Paleozoic is restorated.Based on previous research, The evolution of the western Ordos region and its adjacent area can be divided into four stages which include the northeast-southwest tectono-depositional framework of passive continental margin as a whole from Cambrian to early Ordovician, back-arc basin on the basement of northern Qilian island-arc-basin system from middle Ordovician to Devocian, stable downwarping-type basin from late Carboniferous to middle Permian and western part of great northern-Chinese cratonic basin during late Permian. It is concluded that there are favorable source rock, multitudinous reservoir beds and traps, which are effectively assembled into potential gas-bearing assembly through generation, migration, accumulation and reservation of hydrocarbon in Paleozoic of the western-Ordos region.