Determination of sealing depth of in-seam boreholes for seam gas drainage based on drilling process of a drifter

Zhang, Kai; Sun, Ke; Yu, Bangyong; Ranjith, P.G.

doi:10.1016/j.enggeo.2016.06.006

Cited by 32 publications

(20 citation statements)

References 23 publications

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“…Cross‐boreholes and in‐seam boreholes are usually two types of boreholes layout for gas predrainage . With the increase of mining depth, the difficulty of gas extraction increases in the “three‐high and one low” coal seam whose characteristics are high ground stress, high gas content, high gas pressure, and low gas permeability . Therefore, how to enhance the permeability of coal seam and improve the efficiency of gas drainage, especially complex geological conditions(eg, coal seam with a soft layer), is a difficult problem for experts and scholars all over the world …”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9] With the increase of mining depth, the difficulty of gas extraction increases in the "three-high and one low" coal seam whose characteristics are high ground stress, high gas content, high gas pressure, and low gas permeability. 10,11 Therefore, how to enhance the permeability of coal seam and improve the efficiency of gas drainage, especially complex geological conditions(eg, coal seam with a soft layer), is a difficult problem for experts and scholars all over the world. 12 At present, methods of coal seam permeability enhancement include N 2 injection, deep hole presplitting blasting, 13 hydraulic fracturing, 14 hydraulic flushing, 15,16 hydraulic slotting, and other methods.…”

Section: Introductionmentioning

confidence: 99%

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A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

Qin

Wei

Lou

et al. 2020

Energy Science & Engineering

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Predrainage of gas by cross‐boreholes is an important method to prevent coal and gas outbursts in the process of a coal roadway excavation. Limitations of technologies and poor effects of preventing coal and gas outbursts occur in the coal seam with a soft layer. In this study, a new hydraulic caving technology for cross‐boreholes has been proposed to solve this problem. A CT equipment was used to observe the development of coal fissures around cross‐boreholes in the coal seam with a soft layer. The plastic zone range and permeability distribution of ordinary hydraulic slotting technologies and the new hydraulic caving technology also were compared by numerical simulation. The field test of hydraulic caving was taken in the Xuehu Mine (China). The results show that the fracture development degree of soft coal is greater than that of hard coal at the same distance from cross‐boreholes. The fracture development degree in the plastic zone is greater than that in the elastic zone. The hydraulic caving technique can achieve the same effect as the ordinary hydraulic slotting with less workload. The mass of coal discharged from a cross‐borehole was 1.15 t/m and the average methane concentration of single drainage borehole increased by 1.09‐4.1 times, and the average methane extraction amount of single drainage borehole increased by 6.06 times. Elimination of coal and gas outburst had been completed after 110 days of extraction in the area of hydraulic caving, and Q and S values are lower than the critical value during roadway excavation. It is conclusion that hydraulic caving technique can effectively improve the permeability and rapidly eliminate coal and gas outburst in the coal seam with a soft layer.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

Qin

Wei

Lou

et al. 2020

Energy Science & Engineering

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show abstract

“…erefore, prevention and control of gas disasters is particularly significant. Many scholars have conducted a large amount of research in this area [3][4][5][6]. Some studies focused on sealing materials [7][8][9], while others concentrated on the sealing process [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Sealing Performance of New Solidified Materials: Mechanical Properties and Stress Sensitivity Characterization of Pores

Zhang

Jin

Liu

et al. 2020

Advances in Polymer Technology

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Borehole-sealing solidified material plays a significant role in improving sealing quality and enhancing gas drainage performance. In this study, the MTS815 electro-hydraulic triaxial servo test system and MR-60 NMR test system were adopted to conduct triaxial compression control experiment on the coal sample material, concrete material, and new solidified sealing material, respectively. This paper aims to analyze the difference of support effects, porosity, and stress sensitivity between those materials. Experimental results show that under the same stress condition, the stiffness of traditional concrete solidified material is the largest, while the new solidified material is the second, and the coal sample material is the smallest. Compared with the traditional concrete solidified material, the new solidified sealing material has better strain-bearing capacity and volumetric expansion capacity under each confining pressure in the experiment. The axial strain and volume increment of new solidified material is higher than those of the traditional concrete solidified material at the peak stress. Meanwhile, the confining pressure has a certain hysteresis effect on the postpeak stress attenuation. Fracture has the strongest stress sensitivity in three pore types, and its T2 map relaxation area has a larger compression than adsorption pore and seepage pore under the same pressure. The relative content of seepage pore and fracture in the new solidified material is less than that of coal and concrete samples, and the stress sensitivity of the new solidified materials is weaker than that of coal and concrete materials, thence, new solidified material will have better performance in borehole sealing. Outcomes of this study could provide guidance on the selection of the most effective sealing materials for sealing-quality improvement.

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“…Currently, there are two methods to acquire information during drilling boreholes, which are measurement while drilling (MWD) system and logging while drilling (LWD) system. In the MWD system, the operating parameters of the drifter are recorded, such as drilling rate, rotate pressure, and push force [8][9][10][11][12][13][14][15][16]. en, the condition of the rock mass and state of the drilling machine can be assessed based on mechanical principles or data analysis algorithm.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Comprehensive Real‐Time Methods to Determine Geological Condition of Rock Mass along the Boreholes while Drilling in Underground Coal Mines

Niu

Zhang

et al. 2019

Shock and Vibration

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The geological condition is essential for mining design and disaster control in underground coal mines. The present research focuses on the real-time assessment method on rock mass condition during drilling boreholes. In situ comprehensive experiments were carried out using three methods, which are measurement while drilling (MWD) system, vibration measurement while drilling (VMWD) system, and borehole camera detecting system. In the MWD system, the operating parameters of the drilling machine were recorded, and a dimensionless index Id based on the collected parameters was adopted to assess the geological condition along the borehole. The results show that the state of rock mass can be well classified using the MWD system for both the cross-layer and in-seam boreholes. In the VMWD system, the vibration of the drilling bit was monitored, and the signal was analyzed in both time domain and frequency domain. The results indicate that the rock mass condition can be quantitatively evaluated using the mean square value of the signal and qualitatively estimated using the energy of the spectrum. In the borehole camera system, the photos of the rock mass along the borehole could be well captured, and the identified rock mass condition was used to verify the results of the MWD and VMWD systems. Comprehensive compassion between the results from the three systems shows that all the methods can give valuable information for the geological condition, and the outcomes of the different methods are generally comparable. For practical purposes, the advantages of the involved three detecting systems are discussed.

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Determination of sealing depth of in-seam boreholes for seam gas drainage based on drilling process of a drifter

Cited by 32 publications

References 23 publications

A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

Sealing Performance of New Solidified Materials: Mechanical Properties and Stress Sensitivity Characterization of Pores

Experimental Study on Comprehensive Real‐Time Methods to Determine Geological Condition of Rock Mass along the Boreholes while Drilling in Underground Coal Mines

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