The Research Of Reservoir Characteristics Of The Dengying Formation In Southeast Sichuan

The Dengying Formation in Southeast Sichuan is the emphasis formation for gas exploration and research,and its reservoir characteristics and distribution are the key issues for the gas exploration and prediction in the study area. Guided by carbonate sedimentology,carbonate reservoir,geochemistry and diagenesis,based on field profiles,coring wells and observation of microsection,utilized with the geochemistry methods of cathodoluminescence,carbon and oxygen isotope,strontium isotope,trace element,dolomite degree of order and so on,the paper make a deep research on sedimentary facies,diagenesis,reservoir characteristics and the controlling factors in the development of the reservoir.The Dengying Formation in Southeast Sichuan is a set of tidal flat dolomite,and the reservoir is dominantly distributed over the top and middle of the Dengying Formation. Through the observation of microsection and the analysis of well datas,pore stracture characteristics and physical properties,the study indicates that the main reservoir spaces in Dengying Formation are pores,caves and fractures with secondary origin and the reservoir is fissure-cave type,fissure-pore type and fracture type with low porosity and low permeability.Based on the study of lithology and sedimentary facies,utilized with the analysis of microsection characteristics and geochemical characteristics, the study on diagenesis,diagenesis stage and diagenesis environment in Dengying Formation suggests that compaction and pressure solution,cementation and silicatization are destructive diagenesis,and dolomitization,recrystallization and corrosion are constructive ones,that dolomitization mold mainly concludes penesyngenetic dolomitization,admixing water dolomitization and buried one;The porosity evolution of the reservoir in Dengying Formation is divided into syndiagenetic stage,diagenetic stage,hypergenetic stage,reburial stage and structural stage. According to the analysis of pore evolution and controlling factors of the reservoir in Dengying Formation,the study indicates that the reservoir is controlled and influenced by sedimentary facies,diagenesis and structure,that sedimentary facies are the basis of the reservoir development and controls reservoir distribution;Diagenesis controls the reservoir's ability,and influences evolution of reservoir spaces and pore-structure characteristic,compaction,cementation of periods and silicatization make many primary pores disappear, corrosion of periods and recrystallization are key factors of developing high reservoir;Structural fissures determine current reservoir distribution.