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Energies 2016, 9(9), 698; doi:10.3390/en9090698

A Novel Method for Borehole Blockage Removal and Experimental Study on a Hydraulic Self-Propelled Nozzle in Underground Coal Mines

1
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
2
National and Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seams, Chongqing University, Chongqing 400044, China
3
Songzao Coal-Electricity Limited Liability Company, Chongqing 401445, China
*
Author to whom correspondence should be addressed.
Academic Editor: Mehrdad Massoudi
Received: 17 May 2016 / Revised: 23 August 2016 / Accepted: 25 August 2016 / Published: 31 August 2016
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Abstract

When coal bed methane (CBM) drainage boreholes cross fractured, soft, or water-swelling strata, they collapse and block frequently. Borehole blockages result in a rapid decrease in CBM extraction ability, which leads to a reduction in CBM output and threatens coal mine safety production. To solve these problems, a novel method that uses a self-propelled water-jet nozzle to dredge blocked boreholes in coal seams has been proposed on the basis of the existing technology. Based on a theoretical analysis of the reason for borehole caving and the theory of blockage removal, we optimized the nozzle inlet pressure and selected an appropriate high-pressure resin pipe. A field experiment on the blockage removal of blocked CBM drainage boreholes using the proposed method was run in the Fengchun coal mine, Qijiang, Chongqing, southwest China. In this field trial, the time spent to unblock a borehole varied between 18.52 and 34.98 min, which is much shorter than using a drilling rig. After blockage removal, the average pure volume of the methane drainage of a single borehole was increased from 0.03 L/min to ~1.91–7.30 L/min, and the methane drainage concentration of a single borehole increased from 5% to ~44%–85%. The extraction effect increased significantly. View Full-Text
Keywords: coal bed methane (CBM); blocked boreholes; self-propelled nozzle; high-pressure water jet coal bed methane (CBM); blocked boreholes; self-propelled nozzle; high-pressure water jet
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Ge, Z.; Deng, K.; Lu, Y.; Cheng, L.; Zuo, S.; Tian, X. A Novel Method for Borehole Blockage Removal and Experimental Study on a Hydraulic Self-Propelled Nozzle in Underground Coal Mines. Energies 2016, 9, 698.

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