(518d) Simulation of CO2 Sequestration and Enhanced Coalbed Methane Production in Multiple Appalachian Basin Coal Seams

CONSOL Energy and CNX Gas are performing a pilot injection of carbon dioxide into an Appalachian Basin coal seam as part of DOE/NETL's Sequestration Program. Horizontal wells have been used to produce from the Upper Freeport and the overlying Pittsburgh coal seam since 2004. Injection of at least several thousand tons of CO₂ into the Upper Freeport seam is planned for late 2007, using two of the original production wells. The Upper Freeport seam is found at a depth of about 1,200 feet and is between 0-3 feet thick, while the Pittsburgh coal seam is located at about 700 feet deep and around 5 feet thick. Geologic models of the area are being developed from well logs and seismic information. Models of the coal seams include information on sorption parameters from core samples. Because of the continuing production of coal bed methane from the higher Pittsburgh seam, risks of CO₂ leakage above the Pittsburgh seam are virtually zero. However, because gas volume and mole fractions will be separately monitored in the production streams from both coal seams, this presents a unique opportunity to determine if any migration of CO₂ is occurring between the seams. The state-of-the-art enhanced coalbed methane simulator, PSUCOALCOMP, with our recently developed shrinkage and swelling model, is used to simulate production history and future injection. The presentation will include comparison of simulated results with production history for both coal seams and prediction of CO₂ movement within the Upper Freeport seam. A geomechanical model is used to identify the most likely zones of induced stress within the rocks between the coal seams. Simulation results will be presented on the migration of CO₂ between the two coal seams and the potential increase in production of CO₂ within the Pittsburgh coal seam.