关键词: 淮南矿区, 松软低渗, 地面瓦斯治理, 旋转下套管技术, 煤矿井下验证

Abstract: The Huainan mining area is located at the front of the convergence of the east-west and north-south tectonic zones in China’s land area, with extremely complex geological structures. After a series of structural evolution, the coal seams became fragmented and loose, characterized by high gas content, high formation pressure, high firmation temperature, high confined waterartesian, and soft and low permeability. As the depth of mining in the Huainan mining area has increased year by year, the complexity and danger of gas disasters have significantly increased, and the contradiction between underground gas control and coal mining has become more prominent. The underground gas control and coal mining are closely related. By pre-extracting gas through surface gas exploitation wells, we can effectively control gas disaster accidents and improve the efficiency of coal safety production. We divide the coalfield into units of 5-10-year mine planning designs, and drill surface gas exploitation wells along the trackways and transportation systems of the coal mining faces, with an offset of 30~40 m to cover all the coal mining faces. Using a Third-Section completion method, rotary pipe-setting casing technology, large-scale fracturing with acidic fracturing fluid system, and drainage technology combined with and without sucker rod , we achieved a 100% success rate in the project, the highest sand ratio of 20%, and the highest daily gas production of 11 067 m³ of a well. After verification in coal mines, the original gas pressure in the 13-1 coal seam within 65m and 30m ranges was reduced from 6.8 MPa to 2.7 and 2.4 MPa, respectively, and the gas content was reduced from 11.8 m³/t to 7.2 and 5.2 m³/t, respectively. The fracturing and drainage technology of surface gas exploitation wells have a significant effect on reducing the gas pressure and gas content of the coal seam. Implementing surface gas exploitation technology is beneficial to coal mine safety, energy structure optimization, and carbon emission reduction, ceating a ground gas treatment demonstration area and provide valuable lessons for implementing surface gas exploitation technology in soft and low-permeability coal seam geological conditions in China.

Key words: the Huainan mining area, soft and low-permeability coal seam conditions, surface gas control technology, the rotary pipe-setting casing technology, verification in coal mines