Microscale insights into gas recovery from bright and dull bands in coal

The rate of gas production from coal seam gas reservoirs is highly dependent on coal lithotype, cleat attributes and multiphase flow in cleats. In this paper, we explore and categorize the wettability, roughness data, sorption capacity, and the flow in bright and dull coal lithotypes. The roughness measured on the wall surface of coal fractures indicates different values for each lithotype. Multiphase flow through rough-walled fractures is measured and the pressure variation and relative permeability data are compared for samples from bright and dull bands. Finally, microfluidic experiments are conducted to visualize and analyze the flow in the bright and dull bands. A flow scenario is investigated in which gas is transported through coal regions that have parallel and adjacent lithotypes. It is visualized that the production from these regions can be 53% less than the production from dull band regions. Herein, the impact of coal lithotypes properties on displacement efficiency in coal seams is discussed.