The researchers studied different types of coal in the Hancheng Block, China, to understand how they affect coalbed methane production. They found that bright coal has the best micro-fracture development, while dull coal has more developed adsorption pores. The connectivity of pores decreases from bright to dull coal, impacting porosity and permeability. Bright and semi-bright coal contribute more to permeability than semi-dull and dull coal. The findings suggest that the type of coal affects the permeability of coal reservoirs in the area.