Multiple fractal characterization of medium-high rank coal integrating mercury intrusion porosimetry, N2 and CO2 adsorption experiments

Multifractal features of the pore structures of coal reservoirs control the transport and sustainable production of coalbed methane (CBM), which directly determines the efficiency of CBM extraction and is of great importance for CBM extraction. In order to investigate the multifractal characteristics of the pore structures of medium-high rank coals and their evolutionary trends during coalification, the medium-high rank coal samples from production mines in the Qinshui coal field were collected to investigate the evolution of the multiple fractal characteristics of medium-high rank coals macropores (> 50 nm), mesopores (2−50 nm) and micropores (< 2 nm) during coalification and their influencing factors by using multifractal theories and integrating the mercury intrusion porosimetry, low temperature nitrogen gas adsorption and low temperature carbon dioxide adsorption experiments, respectively. The results show that the generalized dimensional spectrum (Dq−q) and the multifractal singular spectrum (f(α)−α) of