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

Abstract

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.