Simulation on Effects of Injection Parameters on CO₂ Enhanced Gas Recovery in a Heterogeneous Natural Gas Reservoir

Abstract

Abstract CO 2 enhanced gas recovery (CO 2 ‐EGR) is a promising technology to extract additional natural gas from depleted reservoirs with storing CO 2 into underground formations. This work conducted CO 2 ‐EGR simulations in a heterogeneous gas reservoir by using isothermal and non‐isothermal models and systematically analyzed the effects of various CO 2 injection parameters on natural gas recovery, CO 2 storage, and their comprehensive benefits. The results indicate that the CO 2 injection well should be perforated in the lower position, whose overlaid layers with low permeability hinder the upward migration of CO 2 , and the larger natural gas recovery and CO 2 storage can be achieved simultaneously for better comprehensive benefits. The optimal injection rate is 137.29 m 3 ·d −1 to achieve the highest recovery factor of 64.87%. The decrease in injection temperature and the increase in injection pressure are averse to the enhancement of recovery but beneficial to larger CO 2 storage. The comprehensive benefits of natural gas recovery and CO 2 storage are insensitive to the change of injection pressure and temperature, despite that every single one of them is more subjective to injection pressure than temperature. It's hoped that the findings of this work provide some theoretical guidance for the application of CO 2 ‐EGR.