四川盆地新场地区雷口坡组四段上亚段储层特征及发育模式OA

With the intensified exploration and development of the gas reservoirs of the Leikoupo Formation in the Sichuan Basin,the gas reservoirs of the fourth Member of the Leikoupo Formation(hereinafter referred to as the Lei-4 gas reservoir)in the Xinchang area have emerged as a key breakthrough target for marine carbonate rocks in the region.To further elucidate the reservoir characteristics and development model of the lower reservoir interval of the upper Submember of the fourth Member of the Leikoupo Formation(hereinafter referred to as the Lei-43 Submember)in the Xinchang area,a detailed characterization of reservoir characteristics was conducted based on core samples,thin sections,and petrophysical analysis.The dominant controlling factors for reservoir development were discussed,and a development model for the reservoir was established.Results indicate that the lower reservoir interval of the Lei-43 Submember in the study area consists of tidal-flat dolomite reservoirs,which can be classified into four lithological types.Among these,crystalline dolomite and microbial dolomite dominate,followed by calcareous dolomite,with grain dolomite being the least prevalent.The reservoir is developed as thin interbeds.The reservoir space types primarily include algal laminae framework pores,intercrystalline(dissolution)pores,intergranular dissolution pores,and fractures,exhibiting strong heterogeneity and generally characterized by low porosity and low permeability.Reservoir development is influenced by four superimposed processes:First,dolomitization provides the material foundation,with dolomitic flat and algal dolomitic flat sedimentary microfacies becoming favorable reservoir facies belts.Second,penecontemporaneous dissolution controls the distribution of reservoirs,while meteoric karstification improves pore structure.Third,burial diagenesis alters reservoir properties and enhances reservoir heterogeneity.Fourth,faults and fractures enhance connectivity,thereby improving reservoir permeability and scalability.The lower reservoir interval of Lei-43 Submember in the study area follows a development model wherein dolomitization establishes the foundation;karstification enhances porosity;diagenesis modifies heterogeneity,and faults and fractures enhance permeability.Laterally,reservoirs are primarily developed in structural highs within the XS105-XS101D-XS102D well area;vertically,these reservoirs display overlapping distribution with pronounced heterogeneous characteristics.