Influence of pore structure of coal on sensitivity of drillings gas desorption index

Abstract

In order to study the influence of low gas content and high gas pressure of the occurrence of the lower 5# coal seam of Yushuling Coal Mine in Xinjiang on the sensitivity of coal seam drillings gas desorption index, this paper adopted a constant temperature gas release test and low-temperature liquid nitrogen adsorption method to determine the gas adsorption law and pore composition of the coal samples of the lower 5# coal seam of Yushuling and the coal sample of Duanshi No.3 coal seam, to summarize and analyze the influence of pore structure characteristics and gas desorption rate of coal samples with different degrees of metamorphism on the accuracy of drillings desorption index. The results show that: the degree of coal metamorphism and pore structure have a great influence on gas desorption and diffusion rate, and the overall trend of gas desorption rate of Yushuling low-rank gas coal is stable in the first 10 min, while the trend of gas desorption rate of Duanshi high-rank anthracite is faster in the first 4 min and stable in the last 6 min; the correlation between drillings gas desorption index K1 and gas pressure p of Yushuling coal is poorer than that of Δh2, while the correlation between K1 and gas pressure p is better than that of Δh2 for Duanshi coal drillings gas desorption index. The analysis concludes that Δh2 is more suitable as a predictor of the outburst of low-rank coal, and K1 is more suitable as a predictor of the outburst of high-rank coal.

Keywords

• pore structure
• drillings desorption index
• hysteresis loop
• desorption rate
• pore size distribution