Research on and Design of a Self-Propelled Nozzle for the Tree-Type Drilling Technique in Underground Coal Mines

Lu, Yiyu; Zhou, Zhe; Ge, Zhaolong; Zhang, Xinwei; Li, Qian

doi:10.3390/en81212426

Cited by 30 publications

(22 citation statements)

References 18 publications

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“…Next, a self-propelled bit is introduced into the whipstock and negotiates the turn to go into the coal seam. This self-propelled bit is designed [17], so that it can break the coal in the seam and, using high-pressure water jets, drill a sub-borehole the length of which can be as much as 10 m. The bit moves forward under its own self-propelling force generated by backwards-facing water jets. By changing the position and orientation of the whipstock, Energies 2017, 10, 1388 3 of 14 a number of sub-boreholes can be drilled in the coal seam forming the tree-type fracturing net.…”

Section: Tree-type Fracturing Methodsmentioning

confidence: 99%

A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs

et al. 2017

Energies

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Hydraulic fracturing is used widely to stimulate coalbed methane production in coal mines. However, some factors associated with conventional hydraulic fracturing, such as the simple morphology of the fractures it generates and inhomogeneous stress relief, limit its scope of application in coal mines. These problems mean that gas extraction efficiency is low. Conventional fracturing may leave hidden pockets of gas, which will be safety hazards for subsequent coal mining operations. Based on a new drilling technique applicable to drilling boreholes in coal seams, this paper proposes a tree-type fracturing technique for stimulating reservoir volumes. Tree-type fracturing simulation experiments using a large-scale triaxial testing apparatus were conducted in the laboratory. In contrast to the single hole drilled for conventional hydraulic fracturing, the tree-type sub-boreholes induce radial and tangential fractures that form complex fracture networks. These fracture networks can eliminate the "blank area" that may host dangerous gas pockets. Gas seepage in tree-type fractures was analyzed, and gas seepage tests after tree-type fracturing showed that permeability was greatly enhanced. The equipment developed for tree-type fracturing was tested in the Fengchun underground coal mine in China. After implementing tree-type fracturing, the gas extraction rate was around 2.3 times greater than that for traditional fracturing, and the extraction rate remained high for a long time during a 30-day test. This shortened the gas drainage time and improved gas extraction efficiency.

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Section: Tree-type Fracturing Methodsmentioning

confidence: 99%

A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs

et al. 2017

Energies

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“…A limited experimental research on pulsed jet cavitation characteristics has been conducted so far. Photographing the generation process of cavitation jet bubble cloud by the high velocity camera, Lu [17] discovered the elements that affect the bubble cloud length and rock-breaking capability and believed that bubble cloud length is a key indicator of cavitation jet erosion capability. Based on the research carried out, the author conducted an experimental study on the change rule of bubble cloud by using the PIV test technique and to confirm the bubble cloud length.…”

Section: Experimental Study Of Characteristics Of Cavitationmentioning

confidence: 99%

Experimental study on characteristics of self-excited oscillation pulsed water jet

Zhou¹,

Ge²,

Lu³

et al. 2017

J. vibroeng.

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Abstract. To promote the application of self-excited oscillation pulsed water jet in various fields, various characteristics of self-excited oscillation pulsed water jet were studied experimentally. A test system of self-excited oscillation pulsed water jet characteristics was designed, and it is composed of pulsed jet producer devices, particle image velocity (PIV) measuring system, pressure pulse test device and the confining pressure cavity suitable for a PIV test. The characteristics of flow field, pressure oscillation, pulsed cavitation and acoustic shock of pulsed jet were researched. The results showed that the axis velocity vector at nozzle outlet changes periodically, and gradually becomes smaller away from the nozzle. The peak pressure of self-excited oscillation pulsed water jet is 2.5 times higher than the common continuous jet. The wave crest and the wave trough of pulsed jet are not completely symmetric. As the pump pressure increases, the length of bubble cloud increases, and it first increases and then decreases with confining pressure increasing. The vibration acceleration of sonic boom increases and then decreases as pump pressure increases, and decreases steadily with confining pressure increasing.

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“…The front end of the rubber tube is equipped with a hydraulic self-propelled nozzle as shown in Figure 8. A high-pressure pump, model BZW200/31.5 (Liuhe Coal Mining Machinery Co., Ltd., Nanjing, China) was used [32,33]. …”

Section: Testing Equipmentmentioning

confidence: 99%

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

Deng

et al. 2016

Energies

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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.

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Research on and Design of a Self-Propelled Nozzle for the Tree-Type Drilling Technique in Underground Coal Mines

Cited by 30 publications

References 18 publications

A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs

A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs

Experimental study on characteristics of self-excited oscillation pulsed water jet

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

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