A evaluation method of CO₂ sequestration potential in gas reservoirs based on mole balance

Depleted gas reservoirs are one of the favorable sites for underground CO₂ sequestration, and it is vital to evaluate the CO₂ sequestration potential of gas reservoirs. Based on the principle of mole balance in the gas recovery and CO₂ sequestration, production and injection processes, the gas reservoir CO₂ sequestration potential evaluation model was developed, which incorporates the gas state equation and the variation of gas deviation factor with temperature and pressure. With this model, the effects of the gas recovery efficiency and gas deviation factor on the CO₂ sequestration capacity were analyzed. The results show that higher recovery efficiency and gas deviation factor are more favorable for CO₂ sequestration. The CO₂ sequestration potential evaluation for Well L1 in block A, central Sichuan Basin, reveals that the CO₂ sequestration capacity predicted by the presented method considering the variation of gas deviation factor with reservoir temperature and pressure is 27% higher than that estimated by the conventional material balance method. The presented method is valuable for CO₂ sequestration potential evaluation and scheme optimization.