POTENTIAL MINERAL DISSOLUTION IN BLACK WARRIOR RIVER BASIN CAPROCKS UNDER GEOLOGICAL CO2 SEQUESTRATION CONDITIONS

The Black Warrior basin of Alabama contains coal beds that could potentially be used for enhanced coalbed methane recovery using carbon dioxide sequestered from point source pollution sites. This research aims at determining the effects of a sequestration environment on a potential shaley caprock. Within the basin, samples were collected from two regional seals, the shales of the Pottsville Formation and the Parkwood Formation. To better understand what happens to the clay fraction of the seals in CCS environments, the samples were treated at ~ 1400 psi and 90 C to simulate injection conditions at depth. High pressures and supercritical CO2 were attained by using dry ice in the prepared Parr Bomb experiments. Pre- and Post-experiment samples were studied using x-ray diffraction (XRD), wave dispersive x-ray fluorescence spectroscopy (WD-XRF), and atomic absorption (AA). Clay fractions from both formations were shown to contain some smectite, illite, kaolinite and quartz. Preliminary results suggest that during exposure to CO2-enriched brine, samples exhibited a loss of illite as well as CO2/brine induced cation exchange of K+ from clay surfaces. These results, in conjunction with further research, will be used to identify changes in rock/brine compositions related to the mobilization of elements caused by CO2 injection, and provide preliminary information on the long term stability and storativity of these regional seals.