Method for integrated drilling, flushing, slotting and thermal injection for coalbed gas extraction

摘要

A method for combining integrated drilling, flushing and slotting with thermal injection to enhance coalbed gas extraction, applicable to managing gas extraction from microporous, low-permeability, high-adsorption coalbed areas. A gas extraction borehole (2) is drilled within a certain distance of a predetermined drilling, flushing and slotting borehole (9), and, once sealed, is used for gas extraction. An integrated drilling, flushing and slotting drill bit is used to sink the borehole (9), which is then sealed. Concentration variation in the gas extraction borehole (2) is monitored in real time, and when concentration is below 30%, borehole (9) is opened and high-temperature steam is injected by means of a steam generator (8), after which the borehole (9) is again closed. Drilling a drilling, flushing and slotting borehole increases pressure relief space and the surface of exposed coal, relieves stress on the coal body, and increases gas permeability of the coalbed, while the injection of high-temperature steam promotes gas desorption in the coal body, promotes crack propagation around the borehole, and increases channels for gas flow, thus achieving highly efficient extraction of gas from the coalbed.