Pore-scale flow simulation of supercritical CO₂ and oil flow for simultaneous CO₂ geo-sequestration and enhanced oil recovery

Recently, carbon capture, utilization, and storage (CCUS) with enhanced oil recovery (EOR) have gained a significant traction in an attempt to reduce greenhouse gas emissions. Information on pore-scale CO₂ fluid behavior is vital for efficient geo-sequestration and EOR. This study scrutinizes the behavior of supercritical CO₂ (sc-CO₂) under different reservoir temperature and pressure conditions through computational fluid dynamics (CFD) analysis, applying it to light and heavy crude oil reservoirs. The effects of reservoir pressure (20 MPa and 40 MPa), reservoir temperature (323 K and 353 K), injection velocities (0.005 m/s, 0.001 m/s, and 0.0005 m/s), and in situ oil properties (835.3 kg/m³ and 984 kg/m³) have been considered as control variables. This study couples the Helmholtz free energy equation (equation of state) to consider the changes in physical properties of sc-CO₂ owing to variations in reservoir pressure and temperature conditions. It has been found that the sc-CO₂ sequestration is more efficient in the case of light oil than heavy oil reservoirs. Notably, an increase in temperature and pressure does not affect the trend of sc-CO₂ breakthrough or oil recovery in the case of a reservoir bearing light oil. For heavy oil reservoirs with high pressures, sc-CO₂ sequestration or oil recovery was higher due to the significant increase in density and viscosity of sc-CO₂. Quantitative analysis showed that the stabilizing factor (ε) appreciably varies for light oil at low velocities while higher sensitivity was displayed for heavy oil at high velocities.