Optimizing Economic Production in Shale Gas Reservoirs: The Role of CO2 Injection and Fracture Arrangement

Over the past decade, shale gas has become a significant source of energy supply worldwide. However, due to the ultra-low permeability of shale reservoirs, the estimated primary recovery factor through horizontal drilling and multistage hydraulic fracturing technologies remains low. This research studied CO2-enhanced shale gas recovery (ESGR) as an alternative technique to evaluate its impact on shale gas recovery in different fracture arrangements attributed to various well patterns. The study involved building a 3D dimensional reservoir model using CMG-GEM 2015 simulation software and analyzing the influence of reservoir and hydraulic fracture parameters. The results showed that CO2 gas is a promising stimulation method to improve the recovery of methane gas, as well as being sequestrated in unconventional shale gas reservoirs. During continuous injection, the fracture arranged in a staggered well pattern showed to be a promising pattern for methane recovery with 7% more increased recovery compared to the fracture arrangements in an aligned well placement pattern. During huff and puff injection involving different injection scenarios, the results showed that five cycles of injection had the highest recovery of more than 2% for the fracture arrangement in an aligned well pattern compared to the fracture arrangement in staggered well patterns. In addition, injection start time after 10 years of production had higher methane gas recovery in both fracture arrangements for both well patterns, followed by injection after 5 years of production, 3 years, and during the first year of production. Sensitivity analysis was performed using CMG CMOST 2015, and the results show that methane gas production and carbon dioxide gas storage are highly dependent on reservoir and hydraulic conditions. The information obtained from this research work can further help improve the recovery factor during shale gas recovery with different fracture arrangements as a result of well placement patterns, improve the efficiency of optimization and history matching processes, save time and cost to operators, simulate more research, as well as facilitate the mitigation of global warming through CO2 geo-sequestration.