1 、Drilling Process
In conjunction with special hydraulic punching pump vehicle, wireless measurement while drilling system, cable-free three-sided spiral groove drill rod and three-sided spiral groove screw motor, ZYL-17000D drilling rig was used to drill to the design depth in the normal directional drilling process to complete the directional drilling of directional long hole while slagging through clean water.
2 、Punching Process
When reaching the designed depth via the directional drilling, raise the flow rate and pressure (>15MPa) of the hydraulic punching pump vehicle slowly until the high-pressure water cutting is activated, and then start the retreating hydraulic punching operations; in the punching process, adjust the flow rate and water pressure from time to time according to the punching effect, and punch along the whole route from inside to outside or at fixed interval to the hole opening; the coal returned from each punching hole shall not be less than 1m3. The specific punching process is as follows:
(1) Punching at Fixed Interval: The interval between punching holes shall be 10m and the pressure of punching pump shall not be less than 15MPa.
(2) Punching along the Whole Route: Punch the coal section from the hole bottom to the hole opening. Each drill rod should be pulled and rotated repeatedly, and the punching time shall not be less than 20min.
Due to the punching and coal mining, the whole coal seam will be swollen, so as to relieve the pressure and eliminate the outburst. During the test, the influence range of hydraulic punching should be examined to determine the reasonable branch spacing.
3 、Hole Protection Process
After punching the entire hole in accordance with the design punching parameters, pick up the punching tool string from the hole and run the sieve tube directly into the hole; if the coal seam is soft and fractured, pick up the punching tool string after punching and switch to the large-diameter auger drill rod (or fishing drill rod) in conjunction with the large-diameter reamer bit, and run into the sieve tube in the entire section through the large-diameter auger drill rod and large-diameter reamer bit. Through this process, the sieve tube will be run into the entire section for the directional long hole, which ensures the hole-forming performance of the directional long hole and improves the gas extraction rate of the hole.