Deformation and reservoir properties of tectonically deformed coals

Tectonic deformation and pore structure characteristics of tectonically deformed coals (TDC) collected from the Hancheng area, Weibei block, eastern Ordos Basin were characterized through scanning electron microscope, micro-CT, mercury porosimetry and low-temperature nitrogen adsorption experiments. The isothermal adsorption experiment of lumpy TDC was also performed to investigate the gas storage behavior. The results show that the primary layer structure can be observed in cataclastic coals and granulated coals. These coals show sub-angular particles of 1–3 cm. For scaled coals and mylonitic coals, the primary structure and coal bedding have been destroyed, and the coal is sheared with directional arrangement of grains. The pore volume, pore surface area, micro-pore volume and pore connectivity increase with the increase in deformation extent. The CH4 adsorption capacity of coals shows an increasing trend from brittle deformation to ductile deformation. It is concluded that the coal structure, pore and fracture characteristics of TDC control the gas adsorption capacity of coals.