A new molecular simulation study in the Journal of Saudi Chemical Society examines how compressive stress changes methane and CO2 movement in coal. Researchers built molecular models of four coal ranks and applied pressures up to 200 megapascals. They found that stress reduces pore space and generally lowers gas adsorption, but the effect is nonlinear, with adsorption briefly recovering in certain stress ranges before declining again. Methane is more sensitive to compression than CO2 because its larger molecules get blocked in tightened pores. CO2 consistently out-adsorbs methane and diffuses faster, which supports the idea that CO2 injection could help displace methane from deep, stressed coal seams while sequestering carbon underground. The findings give reservoir engineers a molecular-level basis for designing CO2-enhanced coalbed methane and carbon storage projects.
