Low-Temperature Response Characteristics of Coalbed Methane Desorption under High and Low Destruction Degrees.

Abstract

Freeze-coring technology can effectively reduce the amount of gas loss during the sampling process and improve the accuracy of gas content measurements in underground coal seams. In this study, high- and low-damage coals were selected as test objects to investigate whether the freeze-coring technique is universally applicable to inhibit gas desorption in high- and low-damage coals. In this paper, the pore structure of the test coal samples was first tested using an ASAP2020 specific surface area analyzer, and then a nonfreezing and freezing simulation test was carried out on high- and low-damage coals using a self-developed freezing coring response test platform. The results showed that the gas desorption curves of both high- and low-damage coal samples followed the pattern of rapid increase in the early stage, slow increase in the middle stage, and stability in the late stage under both conditions; freezing conditions significantly reduced the gas desorption during the sampling process, and the difference in gas desorption between high- and low-damage coals was reduced; the gas desorption inhibition rate of high-damage coals was higher at an external heating temperature of 60 °C under freezing conditions; at an external heating at an external heat temperature of 90 °C, the gas desorption inhibition rate of low-damaged coal was higher in the early stage, and the gas desorption inhibition rate of high-damaged coal was higher in the later stage; freeze coring had a significant inhibition effect on the gas desorption of both high- and low-damaged coal types, which verified that the inhibition effect of freeze coring on the gas desorption of high- and low-damaged coal samples was universal. It provides a basis for the future application of freeze-coring technology in coal mines.