1. Introduction
In order to realize the advanced control of coal seam gas in the ultra-long working face of Baode County Coal Mine, on the basis of summing up the successful experience of the original 2311m ultra-deep directional drilling, technical improvement and perfection were conducted. The depth of super-deep inseam directional drilling borehole reached more than 2000m, after solving the problems of wire system signal transmission and the influence of sliding drilling on drilling depth and efficiency. In project demonstration, inseam directional drilling borehole extend to more than 2500m deep.
2. Treatment solution
In view of the problem that the existing directional drilling technology and equipment can not meet the requirements for directional drilling depth along the coal seam in the underground for gas control in a large area of super-long working face, it is proposed to use mud pulse wireless MWD system instead of the wire-line MWD system to measure the drilling parameters. It can also avoid the problem that the signal transmission of the wire-line MWD system is affected by the wireline drill pipe. Based on the theory of “cuttings wedge” in horizontal rotary drilling, accurate azimuth and inclination adjustment under the compound drilling state were realized by optimizing the structure of the auger drilling tool and adjusting the drilling process parameters. Thus, the composite drilling scale is further increased, and the pressure of the drilling system is obviously reduced.
3. Construction situation
In January 2019, ZDY12000LD drilling rig, BLY460 mud pump truck and YHD3-1500 mud pulse wireless measurement while drilling system combined directional drilling technology for wireless measurement while drilling independently developed by CCTEG Xi’an Research Institute were used to conduct ultra-long inseam directional drilling boreholes in the second panel of Baode Coal Mine. Drilling operation lasted 20 days and successfully completed the ultra-deep directional drilling with main borehole depth reached 2570 m. This once again created a depth record of underground inseam directional drilling in coal mine. The total footage of single-hole construction is 3164 m, 9 sidetracks were drilled, which reached the top for 8 times, and the bottom for 4 times. The coal seam penetration rate of the borehole is 97%. Borehole diameter is 120 mm. Daily average drilling footage reaches more than 200 m under normal drilling conditions which shows relative high drilling efficiency.
4. Achieved accomplishment
Through the analysis of the adaptability of the key equipment for the 2570 m ultra-deep hole construction, it can be seen that,
(1) Drilling equipment is stable and reliable.
(2) Wireless measurement while drilling system signal is transmitted stably in the ultra-deep hole.
(3) Composite drilling inclination angle control effect is good, and the system pressure parameter drops significantly.
It shows that this set of technical equipment can meet the construction requirements of 2500 m deep directional drilling along the coal seam. The research results can provide an important reference for the construction of ultra-deep inseam directional drilling and the advance control of gas in the ultra-long working face.
5. FAQ
Q1: Why not use the wireline MWD system for construction?
A: The signal transmission of the wireline MWD system is affected by the wireline drill pipe, which can not meet the requirement of gas control in large area of super-long working face for directional drilling depth along coal seam.
Q2: What can your company do in this area?
A: We can solve the main gas drainage problems encountered in the process of mine exploration, construction, production and shut-down.
Q3:What advantages does your company have over other companies?
A: We are committed to the design and construction of coal seam gas control, and has developed a set of coal seam gas control technology and equipment.
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