An Experimental Study to Investigate the Temperature Effect on Permeability of Victorian Brown Coal during CO₂ Sequestration

Carbon Dioxide (CO₂) sequestration in deep coal seams is a potential mitigation option for global warming. In deep coal seams, the temperature is higher (>40°C) which makes the kinetic energy of the gas molecules to be increased. Accordingly, it increases the rate of diffusion and results in reduction of adsorption capacity that affects the coal gas permeability. Among several previous works conducted regarding the temperature effect for coal gas permeability, the attention paid for brown coal is very less which enhance the necessity of a detailed study. Therefore, the main objective of this study is to investigate the effect of temperature on the permeability of Victorian Brown Coal. A series of tri-axial experiments was conducted on brown coal specimens that were collected from Latrobe Valley basin, Victoria. Permeability tests were carried out under 10 MPa confinement for two different temperatures (25 and 40°C). Both CO₂ and N₂ were injected to the sample in various injecting pressures to obtain a proper comparison between the reactive and non-reactive gas permeability. According to the experimental results, CO₂ permeability of coal decreases for higher injecting pressures (at 8 MPa) at lower temperatures (less than 40 °C), due to the process of swelling occurs inside the coal sample during the CO₂ injection. However, the influence of temperature on N₂ permeability was negligible compared to the CO₂ permeability. Basically it may because; N2 is a nonreactive gas which does not make any adsorption or swelling effect in coal matrix like CO₂.