Experimental study on multi-scale pore structure characteristics of tar-rich coal in Yushenfu mining area

Extracting oil and refining gas from oil-rich coal is an important measure to make up for the shortage of oil and gas supply in China. The research on pore development characteristics and permeability of tar-rich coal will help to better develop and utilize tar-rich coal. Taking the tar-rich coal in Yushenfu mining area as the research object, this paper studies the multi-scale pore structure and the whole segment pore characterization of tar-rich coal by such methods as low-temperature liquid nitrogen adsorption, mercury intrusion porosimetry, nuclear magnetic resonance and gas permeability measurement method. Based on the test results of multi-scale pore structure of tar-rich coal, this paper discusses the differences between the pore characteristics of tar-rich coal and traditional low-rank coal. The results show that the micropores of tar-rich coal in Yushenfu mining area is extremely well-developed, accounting for over 70% of the total pores, while the macropores and mesopores are relatively underdeveloped, accounting for only 25%-30%. By comparing the results of the nuclear magnetic resonance test with the combined characterization results of low temperature liquid nitrogen adsorption and mercury intrusion porosimetry, it is found that the latter can better characterize the whole segment pores of coal samples. Compared with traditional low-rank coal, tar-rich coal has a larger pore specific surface area of 27.48 m²/g and low-temperature nitrogen adsorption capacity of 40-50 cm³/g, providing an advantage to extract oil and gas for tar-rich coal.