OXYGEN ENRICHED UCG METHOD

摘要

The invention provides a method of carrying out oxygen enriched underground coal gasification (UCG). The method of underground coal gasification in a coal seam provided with an injection well, a production well and a substantially horizontal wellbore linking the injection well and the production well, including the steps of: (a), inserting a metal casing into the wellbore; (b) injecting air into the wellbore through the injection well; (c) igniting the coal seam while continuing the injection of air into the wellbore; (d) establishing an active gasifier cavity in the coal seam so as to produce UCG product gas; (e) increasing downhole oxygen concentration to a level sufficient to ignite the metal casing inserted into the wellbore; (f) monitoring burn back of the metal casing inserted into the wellbore; and (g) decreasing downhole oxygen concentration until a desired rate of burn back of the metal casing inserted into the wellbore is achieved.