Classification and evaluation of pore throat structure in tight sandstone reservoirs of the Xujiahe Formation in the Central Sichuan Basin
Tight sandstone reservoirs have the characteristics of strong heterogeneity,complex pore throat relationship and poor correlation between porosity and permeability.Taking the tight sandstone reservoirs of Xujiahe Formation in the Central Sichuan Basin as the research object,the full-scale capil-lary pressure curve was established by using high-pressure mercury injection and nuclear magnetic reso-nance method to characterize the full pore size distribution,and the relationship between different pore throat structure characteristic parameters and reservoir macroscopic physical properties was clarified,and the pore throat structure of tight sandstone reservoir was classified and evaluated.The results show that the NMR pore size distribution calibrated by large pores(≥50 nm)in the high-pressure mercury in-trusion experiment can accurately characterize the full pore size distribution.The kurtosis parameters calculated by the full aperture distribution spectrum have a good correlation with porosity,which can be used to evaluate the macroscopic reservoir capacity of the reservoir.The correlation factor calculated by the pseudo capillary pressure curve has a good correlation with the fractal dimension parameters and per-meability,which can evaluate the macroscopic seepage capacity of the reservoir.The pore throat struc-ture of tight sandstone reservoirs in the study area is divided into three categories,from class Ⅰ to class Ⅲ.The reservoir space type changes from the dominant residual intergranular pores to the dominant in-tragranular dissolved pores.The kurtosis gradually becomes smaller,the fractal dimension becomes lar-ger,and the reservoir capacity and seepage capacity decrease.The results provide a basis for improving the exploration and development efficiency of tight sandstone gas reservoirs.
Central Sichuan BasinXujiahe Formationtight sandstone reservoirhigh-pressure mercury injectionnuclear magnetic resonancepore throat structure
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维普
