Research Of Sedimentary Characteristics And Source Rocks Of Upper Permian Linxi Formation In Linxi Area,Inner Mongolia

Upper Permian Linxi Formationwas exposed widely in the eastern Inner Mongolia.For the upper Paleozoic was recognized as the folding and metamaorphic basement of Mesozoic and Cenozoic basins for a long time,the Linxi Formation are neglected in the oil exploration.By the study in the field in recent years,it is indicates that there is no regional metamotphism in the Upper Paleozoic of the estern Inner Mongolia for the dynamitic contact metamorphose and thermal metamorphism with various degree in some areas.The Linxi Formation is the main generating hydrocarbon layers in the estern Inner Mongolia which shows the good prospect of oil and gas resource,would become the new strategic succeed strata.However,the sedimentary enviorment of the Linxi Formation has been in dispute for a long time.In 2013,a team headed by Zhang Yongsheng found marine fossils in Linxi Country,which raised objection to the theory that Linxi area was continental sedimentary environment in the late Permian.Based on this find,this paper selects the Linxi Formation as the research object,by the theory of sedimentology,stratigraphy,tectonics,paleontology,petroleum geology,organic geochemistry and some knowledge of concerning subjects as guides,combined with regional geological background,regional stratigraphic frame,and explicit the evolutionary process of Permian sedimentary and tectonic of the area.Finally some knowledge has been gained as follows:Based on sedimentary facies analyses of typical sections,the sedimentaty facies characteristics of Linxi Formation were illustrated.The main sedimetary facies of Linxi Formation comprise littoral,neritic,bathyal and delta facies.The littoral facies can be divided into the foreshore and nearshore subfacies.The neritic facies can be divided into the nearshore shallow-sea subfacies and offshore shallow-sea subfacies.The bathyal facies was characterized by slope subfacies deposit.The delta facies can be observed delta front subfacies only,which can be further divided into several microfacies such as underwater distributary channel,intertributary bay and front sheet sand.The characteristics of the hydrocarbon source rocks in Upper Permian Linxi Formation were analyzed by using organic geochemistry methods.In this paper,the organic geochemical characteristics of the hydrocarbon source rocks of Linxi Formation are described in detail in the light of the abundance,type,maturity and biomarker of organic matter.The results show that the late Permian Linxi Formation has wide distribution,large thickness,well-developed dar mudstones,and abundant organic matter.The abundance of hydrocarbon source rocks in Linxi Formation get the rank of middle or good.The type of kerogen is mainly of type?,and type ? accout for a little part.Thermal evolution of organic matters has entered the high-over mature stage and consist mainly of dry gas.The comprehensive evaluation of Linxi Formation is lkely to reveal higher shale gas resource prospect,and thus the formation serves as one of the favorable Late Paleozoic shale gas exploration formations in this area.