REGIONAL ANALYSES OF LOWER PENNSYLVANIAN STRATA IN SOUTHEASTERN KENTUCKY TO ASSESS THE POTENTIAL FOR ENHANCED COALBED METHANE PRODUCTION WITH CARBON DIOXIDE

As part of the Southeast Regional Carbon Sequestration Partnership’s (SECARB) analyses of CO₂ storage and enhanced coalbed methane (CBM) production with CO₂ in the Central Appalachian Basin, the Kentucky Geological Survey analyzed the geology of Lower Pennsylvanian strata along the Virginia border. In southwest Virginia, CBM production is dominantly from the Lower Pennsylvanian Pocahontas Formation. Most Pocahontas CBM wells are at depths of more than 1,000 ft and produce from multiple fracked coals. These coals are truncated updip near the Kentucky-Virginia border by the Warren Point Sandstone. Overlying coals in the New River, Lee, Norton, and Wise Formations have also had methane production in Virginia, and are sometimes fracked and produced with deeper coals for larger cumulative coal thickness. Most of the coals that produce from these formations are also truncated updip by conglomeratic sandstones in the Bee Rock Sandstone of Kentucky. Coals do occur at depth in southeastern Kentucky above the Bee Rock Sandstone in the Lower Pennsylvanian Grundy Formation. The Grundy is equivalent to the upper Norton and lower Wise Formations in Virginia. The Grundy overlies the Bee Rock Sandstone, and is capped by the Middle Pennsylvanian Betsie Shale Member of the Pikeville Formation.

There are few coal exploration boreholes of the Grundy Formation in the deeper parts of Eastern Kentucky Coal Field, but subsurface oil-and-gas well logs can be used to correlate parasequences between the marine flooding surface at the top of the Bee Rock Sandstone and the marine flooding surface at the base of the Betsie Shale. The Grundy in this area is 106 to more than 235 m thick, and thickens to the southeast. Grundy parasequences also tend to thicken to the southeast, but are at their greatest depths in the eastern part of the Middlesboro syncline and in the southernmost part of the Eastern Kentucky Syncline near the Pine Mountain thrust fault. Coals at depths in the synclines should have vitrinite reflectance values greater than 0.8 Rmax. Currently, there is no CBM production in Kentucky, but this study highlights those areas that have coals at depth for potential future investigation.