Pore structure and fractal characterization of main coal-bearing synclines in western Guizhou, China

Abstract

The coal pore structure is closely related to the accumulation and migration of coalbed methane (CBM). This study collected 12 coal samples in western Guizhou and used low-temperature carbon dioxide adsorption/desorption (LT-CO2GA), low-temperature nitrogen adsorption/desorption (LT-N2GA) and nuclear magnetic resonance (NMR) experimental methods to systematically discuss the pore structure and fractal characterization of main coal-bearing syncline. The study shows that coal rank is an important reason for the difference of 6 synclines coal reservoirs. Bide syncline and Panguan syncline have similar pore structure and fractal characteristics. As the coal rank increases, the DR–SSA, DA–TPV, D2, DNMR and VL increase linearly, whereas the BET–SSA and BJH –TPV decrease gradually. Moreover, the connectivity between pores decreases with increasing coal rank. A positive correlation is observed between coal rank, BET–SSA, and BJH –TPV and D2, whereas a negative correlation is seen between moisture, ash yield and D2. DNMR is positively correlated with coal rank, mineral content and ash yield, but negatively correlated with volatile matter content. Although the north synclines have good gas content and a good development potential, poor connectivity and high heterogeneity must be valued during the development process.