The physical properties of coal reservoirs affect how easily coalbed methane can be extracted. Low rank coal has looser molecular structure and higher porosity, making it easier for gas to be released. High rank coal, on the other hand, has tighter molecular structure and lower porosity, making gas extraction more difficult. This difference in physical properties influences the efficiency of gas desorption and production. Low rank coal has better potential for development due to its higher porosity and permeability, allowing for easier pressure release during extraction. High rank coal requires techniques like massive fracturing and multilateral well drilling to increase gas yield.