Coalbed Methane

Coalbed methane (CBM) is a form of natural gas extracted from coal beds. In recent decades it has become an important source of energy throughout the world. The term refers to methane adsorbed into the solid matrix of the coal. It is called 'sweet gas' because of its lack of hydrogen sulfide. The presence of this gas is well known from its occurrence in underground coal mining, where it presents a serious safety risk. Coalbed methane, often referred to as CBM, is distinct from a typical sandstone or other conventional gas reservoir, as the methane is stored within the coal by a process called adsorption. The methane is in a near-liquid state, lining the inside of pores within the coal (matrix). The open fractures in the coal (cleats) can also contain free gas or can be saturated with water.