The Study On Of Gas Reservoir Forming Conditions Of Permian Shale In Dunhuang Basin

The Dunhuang basin is a residual basin in the southeast of the Xinjiang Uygur Autonomous Region and the west of Gansu province.At present,many scholars at home and abroad have devoted a lot of research to the normal oil and gas of the Jurassic in this area,but the research on the unconventional oil and gas has never been involved.Therefore,the study on the formation conditions of Jurassic shale gas in Dunhuang Basin has guiding significance in unconventional oil and gas exploration development.On the basis of collecting geological data of predecessors,through field geological investigation,sample collection and comprehensive analysis of laboratory tests,this paper analyzes the characteristics of Jurassic shale development and lithology in Dunhuang Basin.Based on the comparison with North America and China,Sichuan Basin,Ordos Basin shale gas research results,then made a preliminary evaluation of Permian shale in Turpan-Hami basin of gas reservoir forming conditions.The main conclusions are as follows:The mud shale of Dunhuang basin is developed in Wudun sag,Wanyao sag,Hongliugou sag and dam sag.The main development horizons for Permian are Zhongjiangou group and Dashankou group.The shale thickness of the Zhongjiangou group is 30-342.96 m.The shale thickness of the Dashankou group is between 21.26-160 m and the buried depth is 400-2600 m,which meets the standard of the thickness of the continental shale gas shale.The hydrocarbon source rocks in Jurassic are mainly lake phase,followed by delta phase.In the study area,the microfracture of the shale is developed,and the organic matter is bedding or clumps.The organic geochemical characteristics of the Jurassic shale in the study area indicate that the TOC value of the shale of the Zhongjiangou group in the study area is between 1.61-4.82%,which reaches the mid-good hydrocarbon source rock,and the organic matter is of type ?-?.Due to weathering,some of the samples were of type?and reached the mature stage.The TOC value of shale in the Dashankou group ranged from 1.2% to 2.59%,most of the shale samples reached the medium source rock,some of the shale samples reached the standard of good hydrocarbon source rock,and the type of organic matter was type ?.The thermal evolution enter the mature stage.According to the characteristics of shale thickness,burial depth and organic geochemistry,Jurassic mudstone in Dunhuang Basin has shale gas accumulation conditions.