Compositional Modeling to Analyze the Effect of CH(4)on Coupled Carbon Storage and Enhanced Oil Recovery Process

Abstract

The present study is aimed at the development of compositional simulation models of the co-injection of CO(2)and CH(4)during the water-alternating-gas (WAG) process in order to assess the efficiency of carbon capture and storage in combination with enhanced oil recovery (CCS-EOR). The co-injection of CO(2)and CH(4)occupies more reservoir pore volume and causes higher reservoir pressure than CO(2)WAG, thus leading to an enhanced early EOR performance. However, the overall EOR performance of the co-injection method becomes lower than that of CO(2)WAG due to the reduced miscibility and sweep efficiency upon further CH(4)addition. The decrease in gas displacement and sweep efficiency weaken the hysteresis effects upon the residual trapping mechanism. However, the solubility trapping mechanism takes effect because the co-injection generates higher average reservoir pressure than does the CO(2)WAG. The index of global warming potential (GWP) in a mole unit is employed to quantify the carbon storage effects of CO(2)and co-injection WAG cases. According to the index, 1 mole of CH(4)sequestration has the same effects as that of 10 moles of CO(2)for global warming mitigation. In conclusion, the carbon storage effects are enhanced as CH(4)concentration in the WAG increases.