STUDY OF SEDIMENTARY FACIES,LITHOFACIES PALAEOGEOGRAPHIC OF FOUR MEMBER OF XUJIAHE FORMATION OF UPPER TRIASSIC IN THE WEIDONG-ANYUE AREA

The Xujiahe Formation of the Sichuan Basin has huge potential for exploration and development, but its sedimentary facies research results are relatively insufficient, so this is the unique broad area in south of Sichuan Province that has been less explored, has good conditions for hydrocarbon source reservation and shows potential for exploration of more than one storage and productive layer. Based on rock types, sedimentary structures and section structure features, this paper divided the Xujiahe Formation into delta and lake facies, and the former is further divided into delta plain and delta front sub-facies, while the latter only shows the development of shallow-lake sub-facies in the area studied, and then made a study in detail of the compositional features of micro facies of each sedimentary facies. On the basis of the above-mentioned study, with each sub-facies of the Xusi member as map formation units, the authors prepared lithofacies palaeogeographic map for each sub-facies and researched into their time framework of evolution. The results indicated that the sub-facies of the Xusi member are expressed from south to north as delta plain, delta front and shallow lake. The results serve as basic geological data for further prognosis of reservoir..