The Sedimentary Environment And Diagenesis Of Fine-grained Rocks In Lower Jurassic Of Fuling Area,Sichuan Basin

East Sichuan is a favorable oil and gas reserve block in Sichuan Basin.As a typical continental oil and gas bearing formation,the lower Jurassic Ziliujing formation has rich resources and good exploration potential.Based on previous research,combined with field profile,logging,logging data,core observation,thin section identification,XRD analysis,SEM and other experiments,the petrological characteristics,sedimentary and diagenesis of fine-grained sedimentary rocks in Zi'liujing formation of Fuling area are studied.The fine-grained sedimentary rocks in Zi'liujing formation of the study area are mainly mudstone,shell mudstone and shell limestone,and the mineral components are mainly quartz,clay minerals and calcite.Through the testing of major elements and trace elements,the paleoredox conditions,paleoclimate,paleosalinity,terrigenous clastic supply and paleoproductivity were analyzed,and finally the sedimentary paleoenvironment of Ziliujing formation in Fuling area was restored.Through the identification of facies markers and the analysis of single well facies reflecting the vertical change of sedimentary facies,it is determined that the Ziliujing formation in Fuling area,East Sichuan Province is a lake facies mixed sedimentary system mainly composed of carbonate rocks.Three subfacies and seven microfacies types of semi deep lake—deep lake,shallow lake and lakeside can be identified.Finally the sedimentary model can be established.Compaction,cementation,dissolution,metasomatism,recrystallization,clay mineral transformation and organic diagenesis are developed in fine-grained sedimentary rocks.Zi'liujing formation is in the stage B of middle diagenesis.Organic mudstone and organic shell mudstone are the most favorable reservoirs in Da'anzhai member of Yuanba area.