1. Introduction
Anshan Minefield is located in the southeast of Miaohagu mining area in Shaanxi Province, about 38 km northwest of Fugu County town. The northwest of Well-field system is adjacent to the Shaliang minefield and the Qinjin Coal Mine, the south of which is a small coal mining area and a reserved area in the south of Miaohagu mining area, the southwest of which is adjacent to the Sandaogou Well-field system, and the east of which is a Hagushan town prospecting area. In the process of driving 22 coal through the Return Air Gateway of 3203 working face, it is found that the actual goaf of Qinjin coal mine is beyond the goaf area defined by geophysical prospecting results according to the situation of roadway driving and advanced exploration. This caused difficulties for later stage of safe working face layout.
2. Mine water hazard treatment solution
By using directional drilling technology, the goaf boundary caused by 22 coal cross-boundary mining in Qinjin Coal Mine is explored, and the goaf scope is delineated, which provides a basis for the safety layout of coal mining working face in later period.
3. Construction situation
There are 3 directional boreholes and 5 branch boreholes in this project, with a total footage of 1623m. Hole T1 of drill site 1 was drilled to 59m to connect with the goaf, and then moved to hole T2 of drill site 2 to 121m to connect with the goaf again. After consultation with the miners and engineers of the Shanbei mining industry, the hole T3 was drilled 50m apart from the hole T2. After drilling into 795m, water and sediment flowing out from the borehole. The crossing goaf of Qinjin Coal Mine in Sanpan area was successfully explored through 5 branch holes under precise trajectory control.
4. Achieved accomplishment
The drilling project is carried out in strict accordance with the design, accurately controlling the drilling plane and profile trajectory, and the final borehole location has met the design requirements, providing a reliable basis for the later face layout. The application of directional long distance borehole drilling technology and the accurate determination of the extent of the mined-out area across the boundary bring great guarantee to the production safety of Anshan Coal Mine, make the mining layout effective implementation, and ensure the safety and high-efficiency production of the mine.
5. FAQ
Q1: Why is it not possible to fully and only partially identify the extent of the mined-out area?
A:Due to irregular mined-out area caused by indiscriminate mining in small coal mines, directional drilling technology can only point-shaped proved mined-out area and can not directly encircle the mined-out area, according to the requirements of the mine, only a part of the boundary can be found to secure the layout of the face.
Q2: How to keep the trajectory of the main borehole stable in rock stratum in long distance exploration engineering?
A: taking the trajectory control of directional drilling in coal seam as an example, it is required that during the drilling process, the drill cutting can be analyzed in time to determine the horizon, and the position of the coal seam roof and floor is detected under appropriate circumstances, so as to better control the trajectory and travel along the target horizon.
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