Method for recovering methane from a solid carbonaceous subterranean formation

A method for recovering methane from a solid carbonaceous subterranean formation having a production well in fluid communication with the formation and an injection well in fluid communication with the formation, the method comprising the steps of:

• a) processing a gaseous fluid containing at least 60 volume percent nitrogen and at least 15 volume percent oxygen through a cryogenic separator to produce an oxygen-depleted effluent;
• b) injecting the oxygen-depleted effluent into the formation through the injection well at a rate of from about 300,000 standard cubic feet per day to about 1,500,000 standard cubic feet per day, the injection well having a well spacing of from about 1,000 feet to about 5,000 feet from the production well;
• c) thereafter suspending injection of the oxygen-depleted effluent into the formation;
• d) recovering a first methane-containing gaseous mixture from the formation through the production well during at least a portion of injection step b), the first methane-containing gaseous mixture having a first methane-desorbing gas volume percent;
• and
• e) recovering a second methane-containing gaseous mixture from the formation through the production well after performing suspending step c), the second methane-containing gaseous mixture having a second methane-desorbing gas volume percent less than the first methane-desorbing gas volume percent.