Lithofacies Palaeogeography Of The Upper Permian Wu JiaPing Period In The Sichuan Basin

As an important source of oil and gas resources in China,the Sichuan Basin has made new discoveries and breakthroughs in various strata and blocks in recent years.During exploration of the hydrocarbons in the Feixianguan Formation and Changxing Formation in the Puguang area and in Lichuan,western Hubei Province,it was discovered that the Lower Wujiaping Formation has good hydrocarbon generation capabilities and shows a certain reservoir capacity,but previous There is a lack of research on horizons,especially on the study of sedimentary facies,the unclear understanding of facies belts,the unclear boundary and a series of problems that restrict the further exploration and development of the Sichuan Basin.Based on this,this paper analyzes and uses the drilling and logging data from the Sichuan Basin and previous field profile data,adopts the “single factor analysis and multi-factor comprehensive mapping” method,combines the sedimentary facies analysis of single wells in typical wells and the interpretation of the sedimentary facies of the wells.The study identified the lithological characteristics,plane sedimentary facies distribution,and boundary boundaries of the Wujiaping period in the Sichuan Basin,and explored possible source rocks and possible areas of the reservoir.Through comprehensive analysis,the following points were learned:The sedimentary environment of the Upper Permian Wujiaping Formation in the Sichuan Basin is complex and the types of rocks are complex.From the southwest to the northeast as a whole,it Shows the characteristics of lithologic changes from volcanic rocks and pyroclastic rocks-coarse-fine clastic rocks-argillaceous rocks – carbonate-siliceous rocks.The sedimentary facies on the plane of the study area has a transitional trend from terrestrial-marine-continental facies-marine facies,and six types of sedimentary facies have been defined based on the analysis of individual wells and coupled wells.Volcanic facies(upland)-Alluvial Plain(Land)-Coastal Swamp(Sea-Land Transition)-Carbonate Platform(Shallow Sea)-Slope(Deep-Shallow Junction)-Basin/ Trough(Deep Facies)This series Inheritance and distribution.Combined with the distribution map of the sedimentary facies in the Wujiaping period in the study area,it is believed that there are two sets of source rocks in the Wujiaping period of the Sichuan Basin.The first is the Longtan coal source rock formed in the coastal-margin environment of the land-sea interaction zone in the central Sichuan Basin.The focus is on two blocks: Anping 1 well-nv ji well-Bao 61 well and Wu 9 well.This is followed by deep-water black shale,which is located in the deep sediments of the northern part of the Sichuan Basin.It is concentrated in the northwestern Sichuan region in the Puguang-Ming 1-Tieshan 6 and He 12 wells,and the hydrocarbons in the northeastern Sichuan Basin.Source rock is concentrated in the block of West Yunnan 1-Mennan 1 well.The above areas can be used as the favorable source rock distribution area for the Wujiaping period in the study area.The shallow carbonate rocks in the Wujiaping Formation of the Sichuan Basin are U-shaped in the northern part of central Sichuan.The granular rock in the Yuanba-6,Langzhong,and Guangcan2 wells are the most developed and are classified as favorable reservoirs.The development area can be used as the next exploration focus.