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

摘要

Carbon dioxide (CO2) from energy consumption is a primary source of greenhousegases. Injection of CO2 from power plants in coalbed reservoirs is a plausible method forreducing atmospheric emissions, and it can have the additional benefit of enhancingmethane recovery from coal. Most previous studies have evaluated the merits of CO2disposal in high-rank coals. Low-rank coals in the Gulf Coastal plain, specifically inTexas, are possible targets for CO2 sequestration and enhanced methane production.This research determines the technical feasibility of CO2 sequestration in Texas low-rankcoals in the Wilcox Group in east-central Texas and the potential for enhanced coalbedmethane (ECBM) recovery as an added benefit of sequestration. It includes deterministicand probabilistic simulation studies and evaluates both CO2 and flue gas injectionscenarios.Probabilistic simulation results of 100% CO2 injection in an 80-acre 5-spot patternindicate that these coals with average net thickness of 20 ft can store 1.27 to 2.25 Bcf ofCO2 at depths of 6,200 ft, with an ECBM recovery of 0.48 to 0.85 Bcf. Simulationresults of 50% CO2 - 50% N2 injection in the same 80-acre 5-spot pattern indicate thatthese coals can store 0.86 to 1.52 Bcf of CO2, with an ECBM recovery of 0.62 to 1.10Bcf. Simulation results of flue gas injection (87% N2 - 13% CO2) indicate that thesesame coals can store 0.34 to 0.59 Bcf of CO2, with an ECBM recovery of 0.68 to 1.20Bcf. Methane resources and CO2 sequestration potential of low-rank coals of the WilcoxGroup 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 areestimated to be between 6.3 and 13.6 Tcf of methane, with a potential sequestrationcapacity of 1,570 to 2,690 million tons of CO2. Sequestration capacity of the LCB lowrankcoals in the Wilcox Group in east-central Texas equates to be between 34 and 59years of emissions from six power plants in this area.These technical results, combined with attractive economic conditions and closeproximity of many CO2 point sources near unmineable coalbeds, could generatesignificant projects for CO2 sequestration and ECBM production in Texas low-rankcoals.