Influence of coalification on methane diffusion dynamics in middle-high rank coals

Understanding the effect of coalification on diffusion methane in middle-high rank coals (MHRC) is fundamental for optimizing coalbed (CBM) drainage strategies. Safe coal mining relies critically this approach. Hence, CH4 adsorption/desorption experiments and a new model were used to study behavior five different metamorphic degree from China. The results indicate that, as vitrinite reflectance (Ro) increase, Langmuir volume (VL) shows downward trend at first, then increases. Coalification especially third jump (Ro = 1.26%) turning dynamics MHRC. desorption initial coefficient (D0) both show slight decreasing, rapid increasing trend. D0 jumps Ro 1.26%. VL increases alongside that micropores volume. With decrease Raman parameter ID1/IG, VL, within 7200 s all increase. Results changes microporous structure macromolecular coal, which finally affects capacity coal. has positive gas extraction development CBM semianthracites.