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

Abstract

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 are formed within a thermal injection/extraction borehole by means of integrated drilling and slotting technology; a steam generator, is then used to three high-pressure, cyclically temperature-changing steam into said borehole; the steam passing through a spinning, oscillating-pulse jet nozzle 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.