Study on the Difference of CO ₂ Storage in Low-Porosity and Low-Permeability Heterogeneous Reservoirs under the Restriction of Gas–Water Two-Phase Seepage Characteristics

High Resolution Image Download MS PowerPoint Slide The migration of a CO 2 plume within saline aquifers and the assessment of CO 2 storage capacity are critical factors influencing the implementation of CO 2 geological storage engineering and the evaluation of its safety. Previous research has highlighted that the characteristics of gas–water two-phase flow significantly restrict multiphase CO 2 flow simulations and the dynamic prediction of reserves. However, the variations in CO 2 plume migration, reservoir pressure accumulation, and the dynamic prediction of sealed reserves─specifically under the influence of distinct gas–water relative permeability curves in low-porosity and low-permeability heterogeneous reservoirs─remain insufficiently explored. To address this gap, this study employs the Tough/Petrasim simulation tool to develop a CO 2 geological storage model for the Liujiagou Formation in the Yulin area of the Ordos Basin. Various gas–water relative permeability models are utilized to investigate the differences in plume migration, pressure accumulation, and reserve evaluation under their influence, while also assessing the applicability of these models. Additionally, the analysis examines the effect of residual water saturation on CO 2 migration and storage capacity, elucidating the influence of key storage parameters on CO 2 storage effectiveness in the saline aquifers of the study area. The findings are summarized as follows: (1) The model demonstrates that CO 2 storage in saline aquifers is highly dependent on the permeability function, which affects plume migration, pressure accumulation, and storage volume by influencing the effective duration and transformation of CO 2 storage. While the permeability function is the primary determinant, residual water saturation serves as a significant supplementary factor. (2) Overall, residual water saturation is advantageous; however, elevated saturation levels lead to increased pressure accumulation, posing potential risks to storage projects. (3) The relative permeability function exerts the most substantial influence on CO 2 storage capacity, with variations in reserve predictions evident in the supercritical gas storage capacity of both free and residual CO 2, although its impact on dissolution states is limited. (4) Predictions using the VG function are more conservative compared to those derived from the Corey and linear functions, particularly in low-porosity and low-permeability heterogeneous environments.