Analysis Of Sedimentary Facies And Its Control Factors Of Middle Permian In Yining Basin

Permian hydrocarbon source rocks have high abundance of organic matter and a good potential of hydrocarbon generation,but so far,there has not been found shale gas resources of commercial exploitation value in the basin.This study to clarify the middle Permian strata contact relations and development pattern,division of sedimentary facies types,establish the middle Permian sedimentary facies model,in order to further predicting favorable reservoiring geological conditions and resources to provide basic geological exploration potential evaluation.By the field profile observation,to verify the Middle Permian stratigraphic contact relations and development law,also collect a large of sedimentary facies signs,analyze of lithology component,fossils,geochemistry and structural features such as particle size,identify the middle Permian sedimentary facies types,mainly alluvial fan facies,braided fluvial facies,lacustrine facies,braided river delta and subaqueous fan,and the establishment of middle Permian sedimentary facies model.Permian sedimentary environmental evolution experienced three stages:(1)Wulang period of early Permian basin into the rift lake basin stage of development,lake basin evolution stable;(2)Xiaoshansayi period of the middle Permian,due to regional tectonic movement and volcanic activities,has affected the basin sedimentary environment;Hamisite period for weak stretch environment,basin subsidence by gently;Tamuqisayi period,basin once again into the settlement,rift lake basin feature representation;(3)Basiergan period of late Permian,the basin into the failure stage.Major factors controlling sedimentary facies in basin are the following 4 fracture systems:(1)North Keguqin-Borohoro belt(abbreviated as Ke-Bo Belt)fracture;(2)South rim of Haerlik Mountain-north rim of Nalati mountain fracture;(3)Near east-westward fracture;(4)Mid-northeast-and-northwest-ward X shear fracture.