Gas production mechanism in the process of coal tectonic deformation

In this paper, the authors investigated and analyzed the results of high temperature and high pressure experiments on coal conducted both in China and abroad and the chemical structure change and gas production of different grades of coal under the action of different deformation mechanisms and, on such a basis, put forward some new opinions and research targets: ①about the influence of coal deformation on the coal chemical structure: it is found that different deformations, such as brittle deformation and ductile deformation, exert obviously different influencing mechanisms on the structural evolution trend of coal molecules; ②about coal high-temperature and high-pressure deformation experiments: many experimental processes have produced gases, but the majority of experimental design temperatures are too high, and are even higher than experimental coal pyrolysis or splitting temperatures, thus causing the multi-solution property of the gas production mechanism, i.e., whether the gas is formed by coal pyrolysis and even high-temperature splitting or by coal deformation, or whether both actions make the contribution. The utilization of low-temperature deformation experiments in coal is feasible. Coal deformation can occur under the tectonic stress, leading to the production of gas, which may be one of the sources of the exceeded CBM output. The discussion of the conventional physical ideas on coal-absorbed gas is extended in this paper and, according to the phenomenon of exceeded CBM, the gas molecular has a significant chance of existing in chemical bonds of a low bond energy in coal structure.