Numerical investigation of CO₂-carbonated water-alternating-gas on enhanced oil recovery and geological carbon storage

This study investigates the potential of a novel CO₂-carbonated water-alternating-gas (CWAG) injection method for enhanced oil recovery (EOR) and geological carbon storage. The Weyburn fluid data acquired from Canada are used in a compositional reservoir simulation of a CO₂-CWAG case study with seven cycles in order to analyze the effects of carbonated water (CW) upon the oil recovery and CO₂ storage capacity of a multi-phase CO₂/brine/oil system. The study includes an assessment of the CO₂ plume propagation and retention via structural, residual, and solubility trapping mechanisms. The numerical results demonstrate that CO₂-CWAG yields a 6.7% increase in oil recovery compared to continuous CO₂ flooding (from 68.4% to 73.0%) and a 1.4% increase compared to CO₂-WAG (from 72.0% to 73.0%). During the CO₂-CWAG operation, increasing the molarity of CO₂ from 0.0 mol/L to 1.2 mol/L in carbonated water results in a 6.7% increase in the amount of geologically stored CO₂ (from 6191 tons to 6608 tons). In brief, CO₂-CWAG improves not only oil recovery but also CO₂ storage capacity in terms of the three trapping mechanisms, thus making it a promising low-carbon EOR method that could help reduce CO₂ emissions in the oil and gas industry.