Simulation assessment of CO2 sequestration potential and enhanced methane recovery in low-rank coalbeds of the Wilcox Group, east-central Texas

Carbon dioxide (CO2) from energy consumption is a primary source of greenhouse gases. Injection of CO2 from power plants in coalbed reservoirs is a plausible method for reducing atmospheric emissions, and it can have the additional benefit of enhancing methane recovery from coal. Most previous studies have evaluated the merits of CO2 disposal in high-rank coals. Low-rank coals in the Gulf Coastal plain, specifically in Texas, are possible targets for CO2 sequestration and enhanced methane production. This research determines the technical feasibility of CO2 sequestration in Texas low-rank coals in the Wilcox Group in east-central Texas and the potential for enhanced coalbed methane (ECBM) recovery as an added benefit of sequestration. It includes deterministic and probabilistic simulation studies and evaluates both CO2 and flue gas injection scenarios. Probabilistic simulation results of 100% CO2 injection in an 80-acre 5-spot pattern indicate that these coals with average net thickness of 20 ft can store 1.27 to 2.25 Bcf of CO2 at depths of 6,200 ft, with an ECBM recovery of 0.48 to 0.85 Bcf. Simulation results of 50% CO2 - 50% N2 injection in the same 80-acre 5-spot pattern indicate that these coals can store 0.86 to 1.52 Bcf of CO2, with an ECBM recovery of 0.62 to 1.10 Bcf. Simulation results of flue gas injection (87% N2 - 13% CO2) indicate that these same coals can store 0.34 to 0.59 Bcf of CO2, with an ECBM recovery of 0.68 to 1.20 Bcf. Methane resources and CO2 sequestration potential of low-rank coals of the Wilcox Group Lower Calvert Bluff (LCB) formation in east-central Texas are significant. Resources from LCB low-rank coals in the Wilcox Group in east-central Texas are estimated to be between 6.3 and 13.6 Tcf of methane, with a potential sequestration capacity of 1,570 to 2,690 million tons of CO2. Sequestration capacity of the LCB lowrank coals in the Wilcox Group in east-central Texas equates to be between 34 and 59 years of emissions from six power plants in this area. These technical results, combined with attractive economic conditions and close proximity of many CO2 point sources near unmineable coalbeds, could generate significant projects for CO2 sequestration and ECBM production in Texas low-rank coals.