ASSESSMENT OF ENHANCED GAS RECOVERY FROM CO2 INJECTION INTO SHALE GAS WELLS

Abstract

Carbon capture and storage (CCS) technology is considered crucial in mitigating carbon dioxide (CO2) emissions into the atmosphere while allowing continued use of fossil fuels. Current CCS operations are conducted for the purpose of enhanced oil recovery in depleted oil reservoirs and have been storing CO2 in extremely small capacities. In considering the expansion of possible geologic storage options for CCS, many studies have explored the possibility of storing CO2 in shale gas reservoirs with an additional benefit of enhanced gas recovery. Most studies conducted on the topic have utilized reservoir simulation tools to incorporate various fluid behaviour and shale reservoir properties within the model. Instead, this thesis utilizes a simple mathematical model that represents the flow of gas in a shale reservoir as a single-phase, two-component, one-dimensional Darcy flow within a homogenous medium to assess enhanced gas recovery from CO2 injection into shale gas wells. Two different injection and production options are considered: the Huff-n-Puff Method and the Sweeping Method. The Huff-n-Puff Method yielded almost no enhanced gas recovery and was not deemed a viable method of enhanced gas recovery. The Sweeping Method resulted in significant incremental gas production but was considered economically infeasible without the presence of a carbon tax. Although the model used in this thesis captures the most important physical processes of two-component gas flow in shale gas reservoirs, the results implied that the model has limitations that should be addressed in future studies. Further studies on two component gas behavior and heterogeneity in shale reservoirs is warranted to build a more comprehensive model in assessing enhanced gas recovery from CO2 injection into shale gas reservoirs. .