LNMR Study on Microstructure Characteristics and Pore Size Distribution of High-Rank Coals with Different Bedding

Jiajia Liu,Mengqi Shen,Ming Yang,Jianmin Hu,Yingxiang Fang

doi:10.1155/2021/8542630

Jiajia Liu, Mengqi Shen + Show 3 more

Open Access

https://doi.org/10.1155/2021/8542630

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Abstract

In order to study the pore structure characteristics of high-rank coals with different bedding, NMR experiments were carried out for high-rank coals with different bedding angles (0°, 30°, 45°, 60°, and 90°). The results show that the distribution of T2 map of high-rank coal with different bedding is similar to some extent, showing a double peak or triple peak distribution, and the first peak accounts for more than 97% of the total, indicating that small holes are developed in high-rank coal with different bedding, while macropores are not developed. The influence of bedding angle on the fracture proportion is less than 0.3%. Compared with the fracture proportion, the effect of bedding angle on the proportion of microhole, medium hole, and large hole is greater and presents a certain rule. There are certain differences in T2 cutoff value (T2C) of high-rank coal with different bedding. The relationship between bedding angle and T2C conforms to exponential function, and the correlation degree R2 is 0.839. The research results provide a theoretical basis for gas extraction and utilization and prevention of gas disaster in coal mines in China.

Highlights

Coal is the main source of energy in China and plays an important role in China’s economic development
China is rich in coal and coalbed methane reserves, but the conditions of coal reservoirs are complex. e high gas mines account for more than 65%, and the total gas volume is 36 trillion m3
There are few studies on the pore structure of high-rank coals of different bedding through low-field nuclear magnetic resonance technology

Summary

Introduction

Coal is the main source of energy in China and plays an important role in China’s economic development. Erefore, studying the structural characteristics of pores and fissures of different bedding high-rank coal samples has important guiding significance for studying the process of gas “desorptiondiffusion-seepage” and provides a certain theoretical basis for the extraction and utilization of coal mine gas and the prevention of gas disasters in our country. There are few studies on the pore structure of high-rank coals of different bedding through low-field nuclear magnetic resonance technology. High-rank coals and coalbed methane resources are rich in our country, about a third of the total coalbed methane resources; it is of great significance to study the pore structure of high-rank coal with different bedding. Because of the advantages of low-field NMR technology, such as fast detection speed and no damage to test samples, the author collected high-rank coal from Zhongmacun Mine of the coking coal group and used NMR technology to test the pore structure characteristics of high-rank coal with different bedding angles (0°, 30°, 45°, 60°, and 90°). e research results provide a theoretical basis for gas extraction and utilization and prevention of gas disaster in coal mines in China

Basic Theory of NMR

Experimental Method and Process

Experimental Results and Discussion

Conclusions