A new coal seam seepage parameter prediction method based on gas pressure recovery curve for adjacent aquifer environment

Abstract

Gas extraction is the primary approach for safe and efficient coal mining, its final effect depending on the coal seam seepage parameters (coal seam gas pressure and permeability coefficient), which generally reflect the possibility and intensity of gas protrusion. However, this method is limited by the high requirement for measurement of conditions, long duration, and large errors under complicated conditions (e.g., adjacent aquifers). Therefore, this study proposed a new method to accurately obtain the coal seam gas pressure in an adjacent aquifer and introduced an advanced tool for the rapid measurement of coal seepage parameters, which were verified by engineering. Results of the mercury intrusion porosimetry demonstrated that the effective pore percentage of the coal samples was approximately 32.67%, inducing a locally high gas pressure prone zone in the test area. The multi-physical parameter test showed substantial differences in the coal sample properties, pressure distribution, and seepage parameters in the eastern and western regions of the test site. The field engineering verification results of the prediction of gas pressure, showed that the pressure recovery curve method differed from the conventional method by 4–9.6%, but the time required was only 10–50% of the latter. In the prediction of the permeability coefficient, the pressure recovery curve method had an error between 24.63 and 43.32%, and this difference was consistent with the current method when classifying the extraction difficulty. These findings are significant for the determination of gas seepage parameters at coal mines.