Compositional modeling with formation damage to investigate the effects of CO2–CH4 water alternating gas (WAG) on performance of coupled enhanced oil recovery and geological carbon storage

Abstract

This study develops an integrative simulation model of a water alternating gas (WAG) process that co-injects carbon dioxide (CO2) and methane (CH4)–CO2–CH4 WAG—for formation damage caused by asphaltene deposition in an oil reservoir. The influences of CH4 addition into the injection gas stream are analyzed in terms of enhanced oil recovery (EOR) and carbon capture and storage (CCS). Asphaltene precipitation and deposition mechanisms are examined by fluid modeling and compositional simulation, respectively. Fluid modeling is performed using Burke Oil 1 experimental data. Compositional simulation is conducted for a 13-year CO2–CH4 WAG case. Compared with 100% CO2 WAG, addition of CH4 decreases oil displacement efficiency due to reduced miscibility while mitigating asphaltene deposition. This relief of formation damage compensates for oil recovery. The CCS performance of CO2–CH4 WAG is investigated by residual and solubility trapping processes. The overall carbon storage effect of CO2–CH4 WAG is quantified using global warming potential. These results highlight the significance of CO2–CH4 co-injection to improve the performance of CCS-EOR and of integrative modeling with asphaltene for an accurate performance evaluation of CO2–CH4 WAG.