CO2 injection for enhanced oil and gas recovery and its role in carbon storage and utilization in unconventional reservoirs

Enhanced Oil and Gas Recovery (EOGR) methods are increasingly becoming essential components in the future of hydrocarbon production, with CO2 injection emerging as a promising technique for unconventional reservoirs. In addition, the persistent rise in CO2 emissions is a significant environmental concern and requires innovative solutions. Sequestering CO2 in gas shale formations not only addresses this issue but also provides the added benefit of enhancing oil and gas recovery, potentially making the injection of CO2 economically viable. This study presents reservoir-simulation based investigation of shale gas reservoirs for CO2 injection, considering factors such as adsorption, molecular diffusion, natural fractures, and conducting several sensitivity analyses. The success of CO2 injection and methane (CH4) recovery in shale reservoirs depends on various engineering and geological parameters, including operational aspects such as injection volume and time, as well as geological factors like reservoir permeability and porosity. Despite the complexity of these interactions, the study thoroughly investigates the influence of uncertain parameters on the processes of CO2-Enhanced Gas Recovery (EGR) and CO2 storage, identifying the most critical factors controlling these processes. Two CO2 injection scenarios were explored when primary gas production reaches economic limits: (1) CO2 huff-n-puff in a single horizontal well, and (2) CO2 flooding in an injector/producer pair of horizontal wells. The proposed models were employed to analyze the impact of CO2 injection on EGR and CO2 storage. Subsequently, CO2 flooding in a gas reservoir was compared with that in an oil reservoir. The findings contribute valuable insights into the potential of CO2 injection methods for improving hydrocarbon recovery and mitigating environmental concerns.