Key technologies of efficient extraction of coalbed methane (gas) in Guizhou coal mine area

Under the background of “double carbon” goal, how to solve the problem of frequent gas over-limit in high gas mine and efficient surface extraction of coalbed methane in coal mine area, we must find ways to realize efficient cooperative development of coal and coalbed methane resources. Relying on the continuous research of the national “13th Five-Year Plan” and “14th Five-Year Plan” major science and technology projects, closely combined with the reality of Guizhou coal mine “four areas”, research and exploration of coal-bed methane (gas) “four areas” linkage efficient three-dimensional extraction mode and technical system. Due to the special geological conditions of coal mine area, the coal-bed methane extraction and gas control methods are different from traditional coal-bed methane development and underground gas control technologies. Especially in the goaf of coal mine, when the coal seam is goaf, five stress fields are formed in the tendency due to the post-mining release and redistribution of ground stress, resulting in different degrees of impact on the overlying strata in adjacent areas. This brings new challenges to the surface development of coalbed methane or the advance control of gas. Taking Sanjiao Shu Mine in Panjiang Mining area of Guizhou Province as an example, in order to realize efficient extraction of coalbed methane and pressure relief gas in “four zones” under the condition of multi-thin coal seam group development, based on the characteristics of mining area, mining movement, in-situ formation stress distribution and spatial and spatial dislocation, “one zone, one policy” is adopted. It innovated and explored the following high efficiency extraction technology of “four zones” linked Wells in coal mining areas with Guizhou characteristics: ① By laying multi-functional pumping vertical Wells or small inclination oriented Wells in the goaf, it was the first time in Guizhou to realize efficient extraction and development of pressure relief gas in the overlying coal-covered strata and coal-bed methane in the sweet coal seam below the goaf; ② Taking advantage of the characteristics of spatial and temporal dislocation in the production area, the multi-mode extraction mode of “coalbed methane well + relief well + underground drilling” is adopted for the first coal seam mined in the upper protective layer, which realizes the purpose of the upper and lower vertical combined extraction of coalbed methane (gas) Wells and effectively solves the problem of multi-source gas flooding into coal mining roadway and gas accumulation in the upper corner during coal mining under the condition of coal seam group development in Guizhou; ③ In the preparation area and planning area, combined with the terrain and geological characteristics of the two areas, the horizontal well “well factory” + “two pairs of right and wrong” overlapping well layout mode is adopted to realize the efficient extraction of coal bed methane in the plane in advance and pre-pumping of the sweet coal seam and the pressure relief gas in the overlying coal-laden rock in the subsequent mining process, and at the same time to achieve the goal of “replacing the roadway with Wells”; ④ In view of the development of multi-thin coal seam groups in the study area and the development characteristics of “three zones” in the overlying strata after mining, due to the continuous change of the role of “four zones”, the surface coalbed methane Wells are initially deployed in the production area or preparation area, and the “bridge plug bottom sealing + layer selection perforation” technology is adopted to innovate the “transformation” technology of well structure to achieve the purpose of “multi-purpose in one well”; It also provides new technical ideas and accumulated valuable engineering experience for gas management in coal mine area under the condition of multi-thin coal seam group development in Guizhou.