Influence of water on the desorption features of coal seam gas

This paper aims to clarify the effect of water on the desorption and release of coal seam gas (CSG). To this end, lab simulations were combined with field tests to disclose the changes in the amount and rate of gas desorption under different water saturation conditions. The results show that water had an obvious inhibitory effect on gas desorption. Specifically, when the equilibrium pressure and desorption time remained constant, the gas desorption is negatively correlated with the water content of the coal samples; when the water content reached a certain level, the desorption rate no longer decreased with the increase of water. Meanwhile, several water injection tests were carried out on the initial velocity q and desorption rate K1 of the CSG, trying to effectively prevent and control coal and gas outbursts. The tests results reveal that the values of both indices varied greatly with the increase of the water content, when the latter was between 4.5% and 5%. This means the two indices were highly sensitive to water content in this phase. The decrease of the values slowed down as the water content fell between 6% and 6.5%, and stabilized when the latter increased to 9%~10%.To sum up, water injection of coal seam, i.e. using the q value and K1 value as the indicators of outburst hazards, only partially mitigate rather than eliminate the potential threat of gas outburst. Copyright © 2018, AIDIC Servizi S.r.l.