Potential for CO2 Sequestration and Enhanced Coalbed Methane Production, Blue Creek Field, NW Black Warrior Basin, Alabama

Carbon dioxide (CO2) is a primary source of greenhouse gases. Injection of CO2 from power plants near coalbed reservoirs is a win-win method to reducing emissions of CO2 to the atmosphere. Limited studies have investigated CO2 sequestration and enhanced coalbed methane production in San Juan and Alberta basins, but reservoir modeling is needed to assess the potential of the Black Warrior basin. Alabama ranks 9th nationally in CO2 emissions from power plants; two electricity generation plants are adjacent to the Black Warrior coalbed methane fairway. This research project was a reservoir simulation study designed to evaluate the potential for CO2 sequestration and enhanced coalbed methane (ECBM) recovery in the Blue Creek Field of Black Warrior basin, Alabama. It considered the injection and production rate, the components of injected gas, coal dewatering, permeability anisotropy, various CO2 soak times, completion of multiple reservoir layers and pressure constraints at the injector and producer. The simulation study was based on a 5-spot well pattern 40-ac well spacing. Injection of 100 percent CO2 in coal seams resulted in average volumes of 0.57 Bcf of sequestered CO2 and average volumes of 0.2 Bcf of enhance methane production for the Mary Lee coal zone only, from an 80-acre 5-spot well pattern. For the entire Blue Creek field of the Black Warrior basin, if 100 percent CO2 is injected in the Pratt, Mary Lee and Black Creek coal zones, enhance methane resources recovered are estimated to be 0.3 Tcf, with a potential CO2sequestration capacity of 0.88 Tcf. The methane recovery factor is estimated to be 68.8 percent, if the three coal zones are completed but produced one by one. Approximately 700 wells may be needed in the field. For multi-layers completed wells, the permeability and pressure are important in determining the breakthrough time, methane produced and CO2 injected. Dewatering and soaking do not benefit the CO2 sequestration process but allow higher injection rates. Permeability anisotropy affects CO2 injection and enhanced methane recovery volumes of the field. I recommend a 5-spot pilot project with the maximum well BHP of 1,000 psi at the injector, minimum well BHP of 500 psi at the producer, maximum injection rate of 70 Mscf/D, and production rate of 35 Mscf/D. These technical results, with further economic evaluation, could generate significant projects for CO2 sequestration and enhance coalbed methane production in Blue Creek field, Black Warrior Basin, Alabama.