Method for thermal-displacement-type strengthened extraction in drill hole

A method for gas extraction enhanced by thermal displacement in boreholes, comprising drilling boreholes crossing a coal seam or drilling boreholes down the coal seam, the method comprising:

• arranging a plurality of extraction borehole sites at an interval in the coal seam;
• and
• sequentially drilling extraction boreholes, sealing the boreholes, and connecting the boreholes into a gas extraction pipe network for gas extraction, through the following steps:
• a. arranging a plurality of thermal displacement boreholes among the plurality of extraction boreholes in a way that the thermal displacement boreholes and the extraction boreholes are arranged in a staggered manner;
• b. drilling a thermal displacement borehole, inserting a grouting pipe, a return pipe, a heat pipe, and an extraction pipe into the thermal displacement borehole after withdrawing the drill stem;
• connecting the exposed end of the grouting pipe to a grouting pump;
• connecting the exposed end of the extraction pipe to a gas extraction pipe network;
• and installing a heating device on the exposed section of the heat pipe sequentially;
• c. starting the grouting pump to inject grout into the thermal displacement borehole through the grouting pipe, stopping grouting when the grout flows out from the return pipe, and sealing the thermal displacement borehole;
• d. starting the heating device, the heat pipe absorbing heat from the heating device, thereby releasing heat into the thermal displacement borehole continuously, so as to increase the temperature in the borehole and in the coal mass around the borehole, thereby promoting gas desorption from the coal mass in the area and realizing thermal displacement type enhanced extraction;
• and
• e. repeating steps a to d to continue thermal displacement type enhanced extraction in another area;
• wherein in the borehole drilling crossing the coal seam, the distance between center of the extraction borehole and center of terminal end of the thermal displacement borehole is six (6) to eight (8) meters;
• wherein in the borehole drilling down the coal seam, the distance between center of the extraction borehole and center of opening end of the thermal displacement borehole is three (3) to five (5) meters;
• wherein the heating device employs water circulation heating or an electrically heated tube, and
• wherein the heating device is a closed container, which is subjected to a flameproof treatment, a heating element thereof being immersed in water, heated by heating water to heat the heat pipe or isolated from the surrounding environment, heated by heat radiation and heat convection to the heat pipe without direct contact with the heat pipe and without direct contact with air under the mine.