METHOD FOR METHANE RECOVERY FROM COAL SEAM Russian patent published in 2008 - IPC E21B43/00 E21F7/00 

FIELD: mining, particularly methane production from gas-bearing coal seams, mainly of noncommercial ones, as well as of gas-bearing hydrocarbon formations.

SUBSTANCE: method involves drilling wells from ground surface; constructing wells; injecting liquid carbon dioxide obtained by flue gas processing in seam; evaporating liquid carbon dioxide inside seam. Liquid carbon dioxide is injected in seam via injection well under gaseous nitrogen pressure. Gaseous nitrogen is also obtained of flue gas by flue gas separation by compression. Liquid carbon dioxide is evaporated inside seam by gas discharge from injection well with gas pressure decrease to value where carbon dioxide undergoes phase change. Gas discharge from well is followed by flue gas separation to obtain liquid carbon dioxide and nitrogen with sequential carbon dioxide accumulation and nitrogen pressure increase to value providing carbon dioxide distribution over seam inside separator. Then the cycle is repeated to obtain predetermined methane volume from commercial well.

EFFECT: increased quality of produced methane, decreased power inputs and improved environmental safety due to heat power plant flue gas utilization.

1 ex, 2 dwg