Sequestration and Enhanced Coal Bed Methane: Tanquary Farms Test Site, Wabash County, Illinois

The Midwest Geological Sequestration Consortium (MGSC) carried out a pilot project to test storage of carbon dioxide (CO{sub 2}) in the Springfield Coal Member of the Carbondale Formation (Pennsylvanian System), in order to gauge the potential for large-scale CO{sub 2} sequestration and/or enhanced coal bed methane recovery from Illinois Basin coal beds. The pilot was conducted at the Tanquary Farms site in Wabash County, southeastern Illinois. A four-well design— an injection well and three monitoring wells—was developed and implemented, based on numerical modeling and permeability estimates from literature and field data. Coal cores were taken during the drilling process and were characterized in detail in the lab. Adsorption isotherms indicated that at least three molecules of CO{sub 2} can be stored for each displaced methane (CH{sub 4}) molecule. Microporosity contributes significantly to total porosity. Coal characteristics that affect sequestration potential vary laterally between wells at the site and vertically within a given seam, highlighting the importance of thorough characterization of injection site coals to best predict CO{sub 2} storage capacity. Injection of CO{sub 2} gas took place from June 25, 2008, to January 13, 2009. A “continuous” injection period ran from July 21, 2008, to December 23, 2008, but injection was suspended several times during this period due to equipment failures and other interruptions. Injection equipment and procedures were adjusted in response to these problems. Approximately 92.3 tonnes (101.7 tons) of CO{sub 2} were injected over the duration of the project, at an average rate of 0.93 tonne (1.02 tons) per day, and a mode injection rate of 0.6–0.7 tonne/day (0.66–0.77 ton/day). A Monitoring, Verification, and Accounting (MVA) program was set up to detect CO{sub 2 leakage. Atmospheric CO{sub 2} levels were monitored as were indirect indicators of CO{sub 2} leakage such as plant stress, changes in gas composition at wellheads, and changes in several shallow groundwater characteristics (e.g., alkalinity, pH, oxygen content, dissolved solids, mineral saturation indices, and isotopic distribution). Results showed that there was no CO{sub 2} leakage into groundwater or CO{sub 2} escape at the surface. Post-injection cased hole well log analyses supported this conclusion. Numerical and analytical modeling achieved a relatively good match with observed field data. Based on the model results the plume was estimated to extend 152 m (500 ft) in the face cleat direction and 54.9 m (180 ft) in the butt cleat direction. Using the calibrated model, additional injection scenarios—injection and production with an inverted five-spot pattern and a line drive pattern—could yield CH{sub 4} recovery of up to 70%