Abstract The extraction efficiency of high-gas coal seams is low in China with a large number of pre-drainage boreholes. In this study, we analyze the coal seam gas displacement mechanism using liquid carbon dioxide by combining theoretical analysis, experiments, and field tests. Changes of gas displacement efficiency with time under different displacement flow and pressure conditions are determined. We propose a coalbed methane displacement method using liquid carbon dioxide and apply the model in a field test carried out in well No. 2 of the Sangshuping coal mine. The results show that the injection of liquid carbon dioxide in coal seams is a pressure swing adsorption process. The effective displacement radius from the in-situ tests reaches 20 m. The maximum CH4 extraction concentration in the test area is 65%, which is 2.41 times higher than that of the original coal seam (27%). The maximum methane extraction flux rate is 0.884 m3/min, which is 2.34 times that of original coal seam (0.377). Implementation of liquid carbon dioxide displacement coalbed methane technology optimizes borehole arrangement and enhances coalbed methane extraction.

中文翻译：

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桑树坪煤矿注液态二氧化碳优化预抽井提高煤层气采收率的微先导试验

摘要 我国高瓦斯煤层开采效率低，预抽钻孔多。本研究通过理论分析、实验和现场试验相结合，分析了利用液态二氧化碳驱替煤层气的机理。确定了不同驱替流量和压力条件下气体驱替效率随时间的变化。我们提出了一种利用液态二氧化碳驱替煤层气的方法，并将该模型应用于桑树坪煤矿 2 号井的现场试验。结果表明，向煤层注入液态二氧化碳是一个变压吸附过程。现场测试的有效位移半径达到20 m。试验区最大 CH4 提取浓度为 65%，即 2。比原煤层（27%）高41倍。最大瓦斯抽采通量为0.884 m3/min，是原煤层（0.377）的2.34倍。液态二氧化碳置换煤层气技术的实施，优化了井眼布置，提高了煤层气的开采效率。