Study on the Difference of CO₂ Storage in Low-Porosity and Low-Permeability Heterogeneous Reservoirs under the...

The migration of a CO₂ plume within saline aquifers and the assessment of CO₂ storage capacity are critical factors influencing the implementation of CO₂ 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 CO₂ flow simulations and the dynamic prediction of reserves. However, the variations in CO₂ 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 CO₂ 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 CO₂ migration and storage capacity, elucidating the influence of key storage parameters on CO₂ storage effectiveness in the saline aquifers of the study area. The findings are summarized as follows: (1) The model demonstrates that CO₂ 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 CO₂ 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 CO₂ storage capacity, with variations in reserve predictions evident in the supercritical gas storage capacity of both free and residual CO₂, 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.