Borehole Protection Technology of Screen Pipes for Gas Drainage Boreholes in Soft Coal Seams

Shengquan He, Shengnan Ou, Fengxiang Huang, Longzhe Jin, Yanran Ma and Tuo Chen
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Shengquan He: School of Civil and Resources Engineering, University of Science & Technology Beijing, Beijing 100083, China
Shengnan Ou: School of Civil and Resources Engineering, University of Science & Technology Beijing, Beijing 100083, China
Fengxiang Huang: Hefei Industry Investment Group, Hefei 230031, China
Longzhe Jin: School of Civil and Resources Engineering, University of Science & Technology Beijing, Beijing 100083, China
Yanran Ma: School of Civil and Resources Engineering, University of Science & Technology Beijing, Beijing 100083, China
Tuo Chen: Department of Mining and Materials Engineering, McGill University, Montreal, QC H3A 0E8, Canada

Energies, 2022, vol. 15, issue 15, 1-12

Abstract: In this paper, research was carried out on borehole protection technology using screen pipes, aiming to address the problems of gas drainage borehole collapse and low gas drainage efficiency in soft coal seams, which have low gas permeability and high gas content. An experiment was conducted to study the compressive resistance and borehole protection effects of polyvinylchloride (PVC), polypropylene (PP), and acrylonitrile–butadiene–styrene (ABS) screen pipes with different sieve opening spacings. The optimal screen pipe material and sieve opening spacing were determined. The borehole protection effect and gas drainage efficiency using three borehole protection methods, namely, bare boreholes, traditional PVC screen pipes, and new ABS screen pipes, were compared and studied on site, and the influence of pipe diameter on borehole protection efficiency was revealed. The results show that the compressive resistance and borehole protection effects of the three types of screen pipes are in the following order: PVC < PP < ABS. ABS screen pipes can more effectively inhibit boreholes from collapse, and the best borehole protection is achieved with a sieve opening spacing of 50 mm. The field tests showed that the gas drainage concentration of the bare borehole in the creep deceleration stage was 113% higher than that of the borehole protected by the ABS screen pipe and 255% higher than that of the borehole with the PVC screen pipe. The screen pipe began to play a role in borehole protection at the beginning of the stable working stage, as the borehole wall began to deform and collapse. On the 30th day of gas drainage, the gas drainage concentration of the borehole installed with the ABS screen pipe was about 9 times that of the bare borehole due to the collapse and blockage of the bare borehole. The new ABS screen pipe with an outer diameter of 40 mm and a sieve opening spacing of 50 mm had a better borehole protection effect and gas drainage efficiency than the traditional PVC pipe. Proper sizing of the screen pipe diameter can improve borehole service life and gas drainage efficiency. The research results are of great significance for solving the problem of gas drainage borehole instability and for improving gas drainage efficiency in soft coal seams.

Keywords: soft coal seam; borehole collapse; screen pipe; sieve opening spacing; compressive resistance; gas drainage efficiency (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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