This study compared measurement results of total pore volume and pore size distribution of 6 coal samples with different coal ranks by using the Nuclear Magnetic Resonance Cryoporometry (NMRC) and low-temperature nitrogen adsorption BJH method.Meanwhile

the possibility and feasibility of applying NMRC to analysis of coal pore size distribution were evaluated for the first time. Results show that the total pore volume measured by NMRC is significantly larger than that of BJH method for the same coal sample.This is mainly caused by two factors. Firstly

in comparison with the BJH method

the NMRC can measure more closed pores.Secondly

the BJH model itself has some limitations in calculating the pore volumes of most micropores (<10 nm) and some meso-and macro-pores.Measurement results of coal samples with different coal ranks indicate that the total pore volume measured by NMRC shows a trend of decrease followed by an increase with increasing coal rank.This trend is consistent with the trend of the change of coal porosity with increasing coal rank.In contrast

the total pore volume measured by BJH does not match the trend of the change of coal porosity with increasing coal rank

due to the existence of outlier values in the measurement results of BJH method.Compared with the conventional methods

the NMRC has advantages in quantifying coal total porosity.Moreover

the results of NMRC are less influenced by some artificial factors.Thus

NMRC is a new method that can be applied to the measurement of pore structure of unconventional reservoirs.