Research on Multi-scale Pore Structure Characteristics of Deep Carbonate Gas Reservoirs

The strong heterogeneity and diverse reservoir spaces in deep carbonate gas reservoirs make the accurate multiscale characterization of pore structure features a prerequisite for understanding their special seepage mechanisms and achieving efficient development. This study utilizes multiresolution CT images of deep carbonate gas reservoirs to establish 3D digital cores at different scales, finely characterizing and quantitatively characterizing the 3D pore-fracture-vug matching patterns and pore structure characteristics at different scales. The results indicate that: (1) Carbonate reservoirs can be classified into four types based on storage space development: pore type, pore-fracture type (fracture-pore type), fracture-vug type, and vug type; (2) Pores and vugs of varying scales serve as the primary storage spaces, exhibiting dispersed spatial distribution and poor connectivity; (3) Fractures - predominantly small-aperture features (< 1 mm) - form interconnected networks between pores and vugs, acting as critical flow pathways; (4) Despite their low occurrence frequency, vugs occupy a significant proportion of pore volume, substantially enhancing reservoir storage capacity. This study is of great significance for the in-depth investigation of pore structures in deep carbonate reservoirs and the evaluation of storage capacity in such gas reservoirs.