Research On Sedimentary Facies And Reservoir Characteristics Of The Upper Jurassic Penglaizhen Formation In Southwestern Sichuan

Penglaizhen Formation in Southwestern Sichuan is rich in natural gas resources.We have found a lot of Penglaizhen gas reservoirs including Baimamiao,Sumatou as well as Yanjinggou with great potential for exploration and development after years of effort.Guided by the theories of sedimentary petrology,oil and gas reservoir,industrial geology of petroleum as well as data from well logging and logging,I carried out studying on provenance analysis,features of both sedimentary facies and reservoirs for Penglaizhen Formation in Southwestern Sichuan through profile observation,core description and thin sections authentication.The study found that Penglaizhen Formation is comprised of five sedimentary cycles,which are affected by the provenance from north west and north east.Dominated by deltas,this area also develops alluvial fans,rivers,lakes and other different sedimentary facies.Reservoirs in Penglaizhen Formation are mainly formed by lithic feldspathic sandstones and feldspathic litharenite sandstones,as well as some arkose and feldspathic quartz sandstone.Furthermore,reservoirs space can be divided into intergranular dissolved pore,intragranular dissolved pore,residual intergranular pore,moldic pore.Reservoirs physical property is medium-low porosity and low permeability.The advantageous reservoirs are always found in the areas where are affected by the provenance with high-content feldspar.Besides,distributary channels,underwater distributary channels and mouth bars are the sedimentary facies that are favorable to advantageous reservoirs development.Mechanical compaction and cementation are the main diagenesis leading to low reservoir porosity.Moreover,reservoirs property is effectively improved by dissolution,while tectonism has little impact on reservoirs.Longitudinally,reservoirs of Penglaizhen Formation are mainly found in Phase III and IV,second is in Phase V and the least is in Phase I and II.On the contrary,reservoirs distributed on horizontal direction,mainly found in Baimamiao,Sumatou and Yanjinggou,are affected by sedimentary micro-facies,provenance and so on.Along with reservoirs distribution law and exploration&development results,I have preferably chosen 3 and 2 favorable exploration areas from above-mentioned Phased III and Phase IV respectively.