Method for integrated drilling, slotting and oscillating thermal injection for coal seam gas extraction

摘要

A method for combining integrated drilling and slotting with oscillating thermal injection to enhance coalbed gas extraction, applicable to managing gas extraction from microporous, low-permeability, high-adsorption coal seam areas. A number of slots (5) are formed within a thermal injection/extraction borehole (3) by means of integrated drilling and slotting technology; a steam generator (7) is then used to force high-pressure, cyclically temperature-changing steam into said borehole (3); the steam passing through a spinning oscillating-pulse jet nozzle (6) forms an oscillating superheated steam, heating the coal body. The present method overcomes the limitations of simple permeability-increasing techniques, the slotting by means of hydraulic pressure significantly increasing the pressure relief range of a single borehole and forming a fracture network that provides channels for passage of the superheated steam, while oscillating variation in steam temperature and pressure also promote crack propagation and perforation of the coal body; the combined effect of the two enhances the efficiency of gas desorption and extraction.