Geological mechanism and evaluation method on coal-bed methane (CBM) recoverability for low-rank coal in China

Abstract

Aiming to address the production potential and evaluation method of coal-bed methane (CBM) for low-rank coal, taking Coal Seam 4 of Dafosi mine field in Binchang mining area as the research object, the adsorption and desorption experiments, drainage numerical simulation and analysis of the gas production characteristics were carried out. The gas content, coal seam thickness and permeability, and other geological parameter combinations of CBM recoverability were determined. The numerical simulation results reveal that CBM has considerable production potential due to its large thickness and high permeability. Therefore, the geological control mechanism of CBM recoverability is strong desorption capacity, large coal-seam thickness and high reservoir permeability. Combined with the practical analysis, the gas content is the first factor to determine the recoverability. Moreover, the classification evaluation index is established, and the four-level classification index requirements for the optimisation are determined. Furthermore, the concept of CBM enrichment and the high-yield area is defined, and various geological indexes and conditions are specified.

Keywords

• low-rank coal
• coal-bed methane
• resource recoverability
• control mechanism
• evaluation index
• enrichment and high-yield area