Kinetic Modeling of the Sorption of Carbon Dioxide on Powder and Non-powder Bituminous Coal for Sequestration and Enhanced Coalbed Methane Recovery

Abstract

Abstract Geologic sequestration of carbon dioxide is an option for the mitigation of industrial emissions. However, considerable effort remains to shift this technology from its current status as potential solution to a safe, effective and trusted foundation to the global energy system. Characterization of gas movement and sorption capacity of coal at in-situ conditions is required. Using the volumetric method, measurements of CH4 and CO2 sorption and diffusion in coal have been made on powder and non-powder confined coal. Evaluation of sorption capacity and transport rates of gases in coal structure under replicated in-situ conditions is essential. Although crushed coal provides useful information for coal structure characterization, underground storage take place within compact coal monoliths. There is evidence that overburden stresses affects swelling and impacts gas movement in coal. This paper focuses primarily on the characterization of coal-gas system dynamic behavior during carbon dioxide sorption at replicated in-situ conditions. It includes the quantification of the effect of confining stress on sorption capacity and transport rates and its variation with time in coal at constant effective stress. Carbon dioxide sorption rates are evaluated for 1000 psi (6.9 MPa) and 2000 psi (13.8 MPa) confining stress. Information collected from the same coal, but unconfined and crushed allows comparison. Gas evolution curves are evaluated by a developed mathematical model and diffusion constants are extracted. Sorption and transport rates obtained can be used in reservoirs simulators of enhanced coalbed methane recovery and carbon dioxide sequestration in unmineable coal seams.