Sedimentary Characteristics And Hydrocarbon Prospect Evaluation Of Jurassic In The Dunhuang Basin

The investigation of hydrocarbon resources in Dunhuang Basin started earlier,but the overall research level is low,the existence of the basin is not clear,the sequence is not detailed and other issues,these problems caused the depositional system to be unclear of the results.The hydrocarbon show was obtained from the Xican-1 in Wudun sag in 2013,which opened up a new area of hydrocarbon exploration in the Hexi Corridor area.Therefore,it is important to make clear the distribution characteristics of the lower-middle Jurassic sedimentary system and evaluate the hydrocarbon prospect in the basin.This paper studies the Jurassic System of Dunhuang Basin and mainly focuses on the middle-lower Jurassic,with the theoretical guidance of sequence stratigraphy,sedimentology and petroleum geology.Based on the structural evolution of the study area,through the observation of the important outcrops in the basin,and combined with drilling,logging,core and other information to carry out research work.The paper clarifies the characteristics of the source and sedimentary facies and its spatial distribution.Two sedimentary facies models are established and the main sedimentary facies types in the lower-middle Jurassic Jurassic are summarized.There exist five types of sedimentary facies: alluvial fan,fan delta,braided river delta,lake and swamp in the research zone.The study suggests that the sedimentary provenance of Dunhuang Basin is mainly from the North Mountains,Alkin-Qilian Mountains and Sanwei Mountains,and the Sanwei Mountains provide both sides to the north and south sides of the two-way source.Based on the sedimentary facies study,the prospect evaluation of hydrocarbon in the Dunhuang Basin through the evaluation of hydrocarbon source rocks and the combination of reservoirs and the matching relationship among the elements.It is concluded that the quality of source rock in the middle group of the Jurassic in Dunhuang Basin is medium – positive.The Jurassic in the basin can be divided into two sets of reservoirs.The favorable sags are Wudun sag,Aksay sag and Daba sag,and the favorable fades belt of the study area are mainly located in the areas between the braided river delta front and the semi-deep lake.