Study on the Influence of Gas Desorption Characteristics of Different Coal Bodies under Hydraulic Permeability Enhancement

Abstract

To investigate the influence of hydraulic permeability enhancement on the gas desorption and accumulation characteristics of water-bearing coal bodies and deeply implement hydraulic fracturing measures to prevent and control gas disasters in coal seams, isothermal adsorption/desorption tests, low-pressure CO2 adsorption tests, and X-ray diffraction (XRD) tests were performed on anthracite from Anbao Coal Mine in Guizhou and bituminous coal from Huainan Pan’er Coal Mine. The study results showed that the gas desorption by kinds of water-bearing coal samples (anthracite) and bituminous coal (PE) was evidently promoted by stress. After each stress path, differences were observed between coal samples in gas desorption, which, however, presented similar variation trends. The gas desorption of the AB coal samples was greater than that of PE coal samples, and the increment of the limiting gas desorption by the AB coal samples was greater than that by the PE coal samples. The specific surface area of the AB coal samples was larger than that of the PE coal samples, and they both contained hydrophilic minerals and moisture. It was found through field observation that after hydraulic permeability enhancement acted upon water-bearing coal, the desorbed gas passively migrated under the stress action. When the coal body was free from the hydraulic stress action, gas started flowing back. The study results reveal the influence of hydraulic permeability enhancement on the accumulated gas desorption characteristics of water-bearing coal, and will be of theoretical and practical engineering significance for the prevention and control of gas disasters in coal seams using hydraulic measures.