Coal-bed Methane Extraction Technology and Test by Ground L-type Roof Horizontal Directional Well in Mining Area in Coal Mine

In order to solve the problems of underground mining cohesion tension and gas overrun in upper corner, the gas extraction technology by the ground L-type well in the mining area was proposed according to the characteristics of gas extraction by the underground high-level boreholes and the ground vertical wells in the mining area. Based on the deep analysis of the difference between the ground L-type well and the traditional L-type directional well in the mining area, it was concluded that the key points of this technology should include the design of the well structure and the selection of the well horizon, the directional drilling of the well and dredge of the well horizon, and the control technology for ground gas extraction. The test of the gas extraction technology by the ground L-type well in the mining area was carried out in 3313 working face in Sihe Mine of Shanxi Jincheng Anthracite Mining Group, the test results showed that the average gas extraction concentration by the ground L-type well was 80%, the average pure gas extraction volume was 22 000 m³/d, and the gas concentration in upper corner dropped by 46.5% on an average. This technology has played a key role in gas emission control in the working face, and its great potential in the field of coal-bed methane development and gas emission control was verified. So it provided a new technical way for the integrated development of coal and coal-bed methane in China's coal mines.