Advanced core flooding apparatus to estimate permeability and storage dynamics of CO2 in large coal specimens

The ever-increasing carbon dioxide (CO2) emissions into the atmosphere due to human activities are causing a major environmental impact and need to be controlled promptly using innovative technologies. CO2 storage in sub-surface reservoirs such as coal seams with potential for recovering methane is perceived as an efficient technology. However, the storage efficiency of this methodology has not been verified experimentally for various coal types. Although testing has been carried out using coal specimens up to about 100 mm in length, the results have not yet been verified with samples over 500 mm in length. Theories of coal adsorption need to be verified with these types of samples to understand the effect of swelling, shrinkage and storage at a substantial scale. A state-of-the-art core flooding apparatus has been developed to investigate the change of pore pressure along a coal core sample with the adsorption of CO2. The unique core flooding apparatus can accommodate specimens of 203 mm in diameter and up to 1000 mm in length. The pore pressure development along the coal sample due to CO2 injection is monitored at 3 intermediate points, and tests show a reduction in permeability with increasing injecting pressures. By testing a reconstituted coal sample of 832 mm, the permeability was observed to decrease exponentially with the injection of CO2 as well as with increasing effective stress. Due to CO2 adsorption coal sample swelled by 0.12%, 0.16% and 0.05% corresponding to injection pressures of 900 kPa, 1900 kPa and 3900 kPa and axial loads of 3.2 T, 6.4 T and 12.8 T respectively. (C) 2012 Elsevier Ltd. All rights reserved.