Gas desorption characteristics in water-saturated coal and application to in-situ gas pressure assessment
GAO Mingzhong
WANG Zhipeng
SONG Jie
XIE Jing
HAO Haichun
YANG Bengao
JI Bing
LI Yongcheng
Abstract：Accurate determination of in-situ coal seam gas pressure and its desorption behavior is essential for effective gas extraction and outburst prevention.The"deep coal seam in-situ pressure-preserving gas coring method"calculates the in-situ gas pressure based on the gas pressure before and after the coal core undergoes re-equilibration within the pressure-preser-ving chamber.The accuracy of this calculation critically depends on precisely characterizing the volume expansion-pressure re-equilibration process within the coring device.This study inves-tigates the inhibitory effect of moisture on gas desorption through atmospheric pressure de-sorption tests.Continuous expansion desorption tests were conducted to directly simulate the stepwise volume increase process within the corer,revealing the impact of moisture content on pressure evolution.Low-field nuclear magnetic resonance(NMR)analysis elucidated the dual inhibition mechanism of moisture on gas desorption-diffusion:competitive adsorption and pore blockage.Building on these findings,an in-situ gas pressure measurement method was devel-oped and field-validated in a mine in Jincheng,Shanxi Province.The results show that:Mois-ture significantly inhibits gas desorption;under comparable pressure conditions(approximate-ly 2.5 MPa),increasing the moisture content to 5.11％the total desorption volume in 150 min(Q150)is reduced by 72.3％and the desorption volume in the first minute(Q1)by 84.5％compared to dry samples.During continuous expansion desorption(initial pressure:3.33 MPa,five stepwise expansions),the equilibrium pressure decreases linearly with increasing moisture content;the final equilibrium pressure for the sample with 4.85％moisture content is 6.25％lower than the dry sample.Pressure rebound amplitude also attenuates significantly with successive expansions.Field application of the method,which inversely calculates the in-situ pressure using measured pressure data from the pressure-preserving corer and sample pa-rameters,demonstrates high reliability for water-bearing coal seams(moisture content:5.08％-6.68％),with the overall error below 5％compared to the measured in-situ pressure(0.69 MPa).
Keywords：pressure and gas-retaining coringmoisture contentdesorption lawin-situ gas pressure
Publication Date：2025-11-30
Online Publishing Date：2026-01-09(First online date of this platform, not the publication date of the document)
Pages：13( 1388-1400 )