Controlling Factors For Reservoir Development And Pore Evolution Model Of Longwangmiao Formation In Southern Sichuan Basin

Taking the Longwangmiao Formation in the southern Sichuan Basin as the research object,based on previous research results,the outcrops,drilling core observations and sample analysis and test data,as well as drilling geology and logging data were used to analyze the sequence,sedimentation and The diagenesis is studied,and the development and distribution characteristics of Longwangmiao Formation reservoirs are comprehensively analyzed and their controlling factors are established.The main results show that:Three types of upward shallowing sedimentary combinations associated with carbonate grain bank can be identified to in the study area: multi-stage vertical overlapping of grain banks,grain banks-tidal flats(mixed tidal flats),and interbankgrain banks(idal flats).multi-stage vertical overlapping of grain banks mainly develops in the central Sichuan basin,grain banks-tidal flats(mixed tidal flats)mainly develops in southwest Sichuan basin,and interbank-grain banks(idal flats)mainly develops in eastern and southeast Sichuan basin.multi-stage vertical overlapping of grain bank is most conducive to reservoir development,followed by grain banks-tidal flats(mixed tidal flats)combination,and interbank-grain banks(idal flats)reservoir has poor physical properties.It is concluded that the deposition of virgin grain banks,dolomitization and dissolution during Quasi-symbiotic period,and supergene karstification of the supergene diagenesis controll the development of high-quality reservoirs in the Longwangmiao Formation.The diagenesis in the middle and late diagenesis stage has less influence on the reservoir,and only plays a role in adjusting and reconstructing the reservoir.Multi-stage vertical overlapping of grain banks in the middle of the Sichuan basin deposited in a high-energy environment,with a high degree of dolomitization,strong symbiotic karst and surface karst,developed high-quality reservoirs;grain banks-tidal flats(mixed tidal flats)in southwest Sichuan basin have symbiotic dolomitization and dissolution,and superficial dissolution,which are weaker than those in central Sichuan basin,and affected by terrigenous clastic deposits,the degree of reservoirs development is lower than that in central Sichuan basin;interbank-grain banks(idal flats)in southeast Sichuan basin have weak deposition energy,strong seafloor cementation,weak symbiotic dissolution,low dolomitization,and strong compaction in the later stage of diagenesis,development of the reservoir is poor with the lowest physical properties.