Method of increasing the permeability of a coal seam

A method of increasing the permeability of a coal seam adjacent to a wellbore comprising:

• (a) introducing fluid that causes coal to swell into a subterranean coal seam through a wellbore;
• (b) maintaining the injected fluid within the coal seam in a pressurized condition to permit the fluid to contact the coal seam to a desired distance from the wellbore;
• and
• (c) relieving the pressure within the coal seam by permitting the fluid to flow out from the wellbore at a rate sufficient to increase the permeability of the coal seam adjacent the wellbore.

A method of increasing the rate of methane production from a subterranean coal seam penetrated by a wellbore, the method comprising:

• (a) introducing a fluid consisting essentially of liquid carbon dioxide into the subterranean coal seam through the wellbore at a pressure above ambient reservoir pressure at the wellbore and below a fracture pressure of the coal seam;
• (b) maintaining the fluid in a pressurized condition within the coal seam so the fluid will contact the coal seam adjacent the wellbore;
• and
• (c) relieving the pressure within the coal seam by permitting the fluid to flow out from the wellbore prior to the pressure within the coal seam decreasing to a stabilized pressure and at a rate essentially equivalent to a maximum flow rate permitted by the wellbore and surface wellbore control equipment.