Abstract:

The potential of deep coalbed methane (CBM) resource is huge, which makes it a new field in the unconventional natural gas exploration and development. The U.S. and Canada have successfully achieved the commercial development of deep CBM in some area, while exploration and development of deep CBM in China are still limited due to technological limitations. Based on the study of representative publications in recent years, this paper wholly summarized the progress in researches on physical properties of deep CBM reservoirs from the following four aspects: pore and fracture structures, adsorption and desorption characteristics, diffusion and seepage processes of gas in coal reservoir, and the transformability of coal reservoir. Since deep coal reservoirs are located in complex geological environments with high temperature, high pressure and high stress; thus, the permeability evolution of coal reservoir, the equilibrium relationship among CBM adsorption, desorption, diffusion and seepage, as well as the stress and strain behavior of coal tend to be more complex. Therefore, the studies of the evolution mechanism of deep coal reservoir properties under special geological conditions have theoretical and practical significance for the exploration and development of deep CBM in China.

Key words: deep CBM, reservoir, pore and fracture structure, mechanical property, gas content, permeability