1. Introduction
The coal-bearing strata of Selian No. 2 Mine in Ordos is the Jurassic Yan'an Formation strata, with 9 main mineable coal seams. Water accumulated in abandoned 12206 working face of the 2-2 middle coal seam affects gate entry safe heading of 12307 working face. Conventional drilling for advanced water exploration requires temporary drilling sites and multiple construction rounds, which affects the speed of gate entry heading and severely restricts the replacement of working faces. In order to speed up the tunnel excavation of the 12307 working face, Selian No. 2 Mine decided to adopt underground directional drilling technology to drain water efficiently from abandoned goaf area.
The main difficulties are tight construction period, easy blockage of drilling, large amount of trajectory control, and high drilling risk. The 12408 working face is planned to be installed within 20 days, so the total construction period of equipment entry, drilling construction, transfer, and dismantling must be controlled within 20 days. The borehole track needs to be avoided gate entry of 12308 working face which bring high requirement of borehole trajectory control. Indeed, the integrity of the rock formation near the mined-out area is destroyed, thus, drilling may encounter a higher risk of stuck hole.
2. Solution
Following steps were used by CCTEG Xi’an Research Institute to conduct directional drilling,
(1) Reasonably organize the construction: the drilling section is drilled with circulating water, which reduces the impact of insufficient water supply on the construction period. Water glass is added when sealing the casing to solve the problem of long solidification time for pure cement slurry.
(2) The drill pipe is not lifted out immediately after drilling through the goaf area. and the borehole was cleaned with a large pump volume for 8 hours. Then the method of drilling while cleaning was adopted to flush the bottom of the hole and the silt and rock powder in borehole annular as much as possible.
(3) When the construction period permits, insert the rotary drilling tool for annular cleaning.
(4) Reasonably design the trajectory to make the drilling length as short as possible.
3. Construction situation
2 directional drilling borehole and 1 branch borehole were constructed. The final borehole diameter is φ98mm and the total footage is 934.5m.
4. Achieved accomplishment
Through the construction of this project, the mine can detect the remaining empty water pressure and the amount of water in the 12206 working face within the specified time. The maximum water discharge volume is 44m3/h, and the water pressure is reduced to a safe level within the specified time. It provides effective guarantee for safe and rapid tunneling of gate entry in 12307 working face.
Hot Tags: goaf water detection and discharge, China, manufacturers, suppliers, factory, wholesale, price list, buy, for sale,
