Central Appalachian Basin Unconventional (Coal/Organic Shale) Reservoir Small Scale CO 2 Injection Test
The Virginia Center for Coal and Energy Research (VCCER) project, “Injecting Carbon Dioxide into Unconventional Storage Reservoirs in the Central Appalachian Basin, with an Emphasis on Enhanced Coalbed Methane Recovery (ECBM), to Validate Prior Geological Characterization,” successfully completed two unique field projects: (1) a 510 ton scale ‘huff-and-puff’ carbon dioxide (CO 2 ) injection into a legacy horizontal Chattanooga Shale well in Morgan County, Tennessee and (2) a 13,263 ton CO 2 injection into 3 legacy coalbed methane (CBM) wells in Buchanan County, Virginia. The results from this Morgan County shale injection test confirm the injectivity and storage potential of CO 2 in organic shales formations while enhancing gas recovery. During the flowback phase, gas composition and flow rate were frequently monitored. Results indicated that there was a significant increase in gas flow rate during the first five months of the flowback phase and there was also a significant increase in gas quality, such that the percent composition of NGLs (natural gas liquids), including ethane, propane, and butane, increased. The primary objective of the research is to test the injectivity of CO 2 into unmineable coal seams and the potential for enhanced coalbed methane recovery (ECBM) by stressing the coals under continuous injection for a one-year period. The results from the Buchanan County ECBM test provided data to better understand the effect of matrix swelling, due to the adsorption of CO 2 on the coal surface, on injectivity and ECBM. During the greater than 13,000-ton injection, injectivity was maintained and coal swelling reduced by injecting into multiple wells at a moderate injection rate. Flowback has recently commenced and will be instrumental in determining the ECBM potential of central Appalachian coals and identifying commercialization opportunities.