Multi-scale CT Scanning and Digital Rock Modeling of Tight Sandstone Reservoirs

The digital rock technology based on CT scanning enables three-dimensional visualization and quantitative characterization of rock microstructure. In this study, the tight reservoir rock samples from the Keshen Gas Field in the Kuqa Depression of the Tarim Basin were investigated. High-resolution micrometer CT scanning and FIB-SEM scanning were employed to obtain the microstructural parameters of the tight sandstone reservoir. Three-dimensional image reconstruction and pore structure identification techniques were used to establish a three-dimensional digital rock model, and the model was scaled up to ensure consistency with laboratory test results. The results showed that the CT scanning of plug samples revealed a uniform texture and dense structure in the Keshen area, with dispersed pores and poor connectivity. The FIB-SEM scanning identified three types of samples: dense, porous, and fractured. Half of the pores had a radius smaller than 20 nm, and less than 10% of the pores had a radius larger than 1 μm, indicating a high overall level of tightness in the rock core. Digital rock models at the nanometer and micrometer scales were established based on the scanning results, and the permeability of the scaled-up digital rock model showed high degree of agreement with the laboratory measurements. The multi-scale CT scanning-based digital rock modeling technology has bridged the gap from traditional two-dimensional representation to three-dimensional representation of tight sandstone reservoirs, facilitating further research on the microscale flow mechanism and the development of rational reservoir exploitation techniques.