Evaluation of enhanced coalbed methane recovery and carbon dioxide sequestration potential in high volatile bituminous coal

Abstract

Geologic sequestration of carbon dioxide (CO2) captured from flue gas into deep unmineable coal seams is a promising option to mitigate greenhouse gas emissions. Also, the injection costs can be partially or entirely offset by the revenue generated through the additional methane recovered. Complex phenomena occur during primary coalbed methane (CBM) recovery and CO2 injection for enhanced methane production and CO2 sequestration (CO2-ECBM). Numerical modeling and simulations can be used to represent these complex phenomena.This research investigates the CO2 storage capacity and CO2-ECBM recovery potential of a high volatile bituminous coal (Ferron coal) in Buzzard Bench, Uinta Basin. It is one of the most recognized coalbed methane producing areas in the U.S. and high-graded for evaluation due to its proximity to coal-fired power plants and CBM activity history. A three-dimensional geological model was first constructed with information available from the public domain. Available gamma-ray and density logs were utilized to develop the three-dimensional model of the coal seam and the overlying rocks using geostatistical techniques. This allows heterogeneity to be introduced in both vertical and horizontal directions, thereby creating a representational geologic model. After that, a dynamic reservoir model was constructed and calibrated against actual methane production using a history match. Simulations of CO2 injection and collateral methane production were carried out after the history match using two injectors and two production wells.The fluid flow simulation results demonstrated that it may be feasible to inject 1.16 million tons and sequester 1.15 million tons of CO2 over 20 years. Additionally, 13.95 billion cubic feet of methane were recovered within the same period. Due to the permeability reduction by coal matrix swelling, the methane recovered decreased by 19%, while the volume of CO2 injected decreased by 29%. This demonstrated injection feasibility, even in the presence of potential permeability reduction by coal matrix swelling during CO2 injection. Injection and production strategies are suggested to maximize injectivity and sequestration to overcome problems resulting from permeability changes and override.