Reservoir Characteristics And Controlling Factors Of The Middle Triassic Leikoupo Formation In South Sichuan Basin

As research object,the Middle Triassic Leikoupo Formation in Jianyang-Zigong area are analyzed through thin sections,scanning electron microscope,physical properties and logging datas to studying reservoir characteristics,sedimentary characteristics,reservoir rock types,diagenesis types,reservoir space types,reservoir properties,reservoir distribution characteristics and its controlling factors.Dolomite,limestone and transitional rocks are main rock types in the Formation.High-quality reservoir basically developed in grainstone and fine-grained dolomite.The formation of grain dolomite is related to penecontemporaneous dolomitization and fine dolomite reservoir developed many dolomite intergranular pores.Reservoir spaces include intragranular dissolved pore and intergranular dissolved pore because of dissolution.The types of sedimentary facies of the reservoir of the Leikoupo Formation are mainly limited platform and evaporative platform facies.T₂L₁ and T₂L₂ developes lagoon and flat deposit,T₂L₃ developes lagoon deposit,and high quality reservoirs are developed in T₂L₁¹ and T₂L₃³.As a whole,the reservoir physical property is low porosity and low permeability in the Leikoupo Formation in the Southern Sichuan Basin.The average porosity of T₂L₁ is 7.1%,while 1.04%in T₂L₂ and 1.35%in T₂L₃.Permeability of T₂L₁centrally distributed in lower 0.1mD,and permeability of T₂L₃ iSouth is mainly distributed in 0.01mD⁰.1mD in the study area.Reservoir qualities are affected by sedimentation facies and diagenesis which are aimed to controlling rock types,space types and sendimentary environment respectively.Besides,T₂L₃ also affected by karstification and structural fractures which are created by tectonization.The main control factors of the reservoir are sedimentary facies,dissolution and dolomitization according to he distribution and thickness of the reservoir.The reservoir of the Leikoupo Formation is divided into two sets according to the location of reservoir and cap rock in vertical.One is grainstone reservoir distributed in T₂L₁¹ in northern Ziyang region and the other is grainstone and fine-grained dolomite reservoir which distributed in T₂L₃³ in northern Ziyang and Weiyuan region.