Carbon dioxide sequestration and enhanced coalbed methane recovery in unmineable coalbeds of the Powder River Basin, Wyoming

The first problem addressed in this thesis is global warming, where it has been shown that the amount of carbon dioxide (CO2) in the atmosphere has risen from pre-industrial levels of 280 ppm to present levels of ∼380 ppm. This increase in atmospheric CO2 is attributed to the world's expanding use of fossil fuels and is believed to be one of the primary causes of global warming.; To examine the feasibility of sequestering CO2 in unmineable coalbeds of the Powder River Basin (PRB), Wyoming, a reservoir characterization study and fluid flow simulations have been carried out. The results suggest that after 13 years of CO2 injection, ∼99% of the total CO 2 injected into the Big George coal would be sequestered (assuming the coalbed is overlain by an impermeable caprock), that methane production would be ∼5-8 times greater with CO2 injection than without, and that one injection well would be able to sequester ∼9 kt of CO2 a year.; The second issue addressed in this thesis is the disposal of coalbed methane (CBM) water, which is co-produced with CBM in the PRB. CBM water poses a serious environmental hazard to the PRB because the water has high saline and sodium contents, making it unsuitable for agricultural use and damaging to wildlife habitats. One option for the disposal of CBM water is injection into aquifers. To determine if pore pressures in aquifers are low enough to allow for significant CBM water injection and to determine whether the coals and sands are in hydraulic communication with each other, pore pressures in 250 wells that monitor water levels in coalbeds and adjacent sands within the PRB have been calculated. The analysis indicates that both sands and coalbeds have sub-hydrostatic pore pressures and that at present all sand aquifers in hydraulic communication with a producing coalbed are within ∼200 ft of the coalbed. Therefore, in order to be sure that disposed CBM water does not migrate back into producing coalbeds over time, CBM water disposal should be undertaken in sub-hydrostatic sand aquifers that are not in hydraulic communication with a coalbed.