CARBON SEQUESTRATION: RESERVOIR CHARACTERIZATION AND POTENTIAL OF EARLY PENNSYLVANIAN BREATHITT GROUP, CENTRAL APPALACHIAN BASIN

Early Pennsylvanian sedimentary rocks within the Breathitt Group of southwest Virginia, eastern Kentucky and southern West Virginia have become an emerging coal bed methane resource and carbon sequestration target within the Central Appalachian Basin. USGS assessments for total undiscovered resources of coal bed methane suggest at least 3.5 TCF in the Pocahontas Basin alone, highlighting exploration opportunities on the margins of the current CBM development fairway (Milici, 2002). Recent investigations by the Southeast Regional Carbon Sequestration Partnership suggest these coal-bearing sedimentary rocks are capable of storing significant volumes of injected CO2 while simultaneously enhancing CBM production.

The construction of several cross sections across the Nora CBM field uses interpreted textural changes in hundreds of geophysical well log suites and several cores to illustrate laterally regional expression of base level controls on lithologic changes within the Pocahontas Basin. Overall, the Breathitt Group displays a general fining upward pattern from the sandstone dominated Pocahontas Fm. through the numerous coal seams and associated heterolithic strata within the Bottom Creek Fm. into the increasingly shale dominated Alvy Creek Fm. This textural trend suggests a prolonged episode of accelerating tectonic subsidence, changing from being generally overfilled with dominantly fluvial sediments to increasingly estuarine deposits as basin subsidence exceeded rates of sediment supply and deposition.

Critical to the goals of carbon sequestration within coal seams is the ability of surrounding strata to contain the injected CO2 plume. Several continuous cores donated from industry partners allowed the investigation of facies successions and integration with well log data to support sequence interpretations of Early Pennsylvanian stratigraphy. Petrographic, porosity & permeability testing of a variety of shale, siltstone and heterolithic facies define the CO2 trapping characteristics of strata overlying injection target coals. Subsurface mapping of the occurrence and distribution of CO2 sealing facies provides the necessary data required to provide assurance that injected CO2 does not find its way to the surface through primary permeability pathways controlled by lithology.