Gas Flow Characteristics and Optimization of Gas Drainage Borehole Layout in Protective Coal Seam Mining: A Case Study from the Shaqu Coal Mine, Shanxi Province, China

The height of the water-conducting fractured zone (WCFZ) is a basic parameter related to water protection in coal mines and is also crucial for aquifer protection and mine safety. In order to accurately detect the height and shape and reveal the formation mechanism of the WCFZ, which is caused by middle-deep coal seam mining in a sandy region, the 112201 coalface at the 1# coal mine of Xiaobaodang was taken as a case study. Filed measurements including fluid leakage, borehole TV, and similar simulation were adopted to analyze the regularity of the WCFZ in this area. The detection results of field measurements showed that the maximum height of the WCFZ was 177.07 m in a borehole near the open-off cut, and the ratio of the height of the water-conducting fractured zone divided by the mining thickness was 30.53. The WCFZ acquired an inward-convergent saddle shape, which was inclined to the goaf. The saddle bridge was located at the boundary of the goaf, and the saddle ridge was located at the center of the goaf. Also, through analyzing the results of similar simulations, we found that, in the process of mining, separation cracks and the beam structure were the main forms of overburden disturbance transmitting upward and ahead of mining, respectively. The main cause of the increase in height of the WCFZ was the connection of the separation cracks and vertical cracks caused by fractures of beam structures. The development of the WCFZ was divided into five stages: incubation stage, development stage, rapidly increasing stage, slowly increasing stage, and stable stage. Moreover, the duration of each stage was related to the lithology and mining technology. This research can provide significant theoretical insights for the prediction of the WCFZ, enabling the prevention of water hazards on mine roofs and assisting with water resources protection.

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An approach for water-inrush risk assessment of deep coal seam mining: a case study in Xinlongzhuang coal mine

Environmental Science and Pollution Research ◽

10.1007/s11356-020-10225-0 ◽

2020 ◽

Vol 27 (34) ◽

pp. 43163-43176

Author(s):

Qixiong Gu ◽

Zhen Huang ◽

Shijie Li ◽

Wei Zeng ◽

Yun Wu ◽

...

Keyword(s):

Risk Assessment ◽

Coal Seam ◽

Coal Mine ◽

Water Inrush ◽

Seam Mining

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Speculum Observation and Trajectory Measurement in Gas Extraction Drilling: A Case Study of Changling Coal Mine

Geofluids ◽

10.1155/2021/5545067 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Enbiao Zhao ◽

Kangnan Li ◽

Xin Yang ◽

Nan Deng

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Efficient Production ◽

Drilling Process ◽

Coal Seams ◽

Adjacent Layer ◽

Gas Drainage ◽

High Level ◽

Trajectory Measurement ◽

Drainage Borehole

Coal will still be China’s basic energy for quite a long time. With the increase of mining depth, gas content and pressure also increase. The problems of gas emission and overrun affect the safety and efficient production of coal resource to a certain extent. In this work, the field test of gas drainage borehole peeping and trajectory measurement in coal seam of Changling coal mine are carried out. These coal seams include C5b coal seam, upper adjacent C5a coal seam, C6a coal seams, C6c in lower adjacent strata, and C5b coal seam in high-level borehole. The view of gas drainage borehole peeping and trajectory measurement in the working seam, upper adjacent layer, lower adjacent layer, and high position are obtained. It is found that the hole collapses at the position of about 20 m in both adjacent strata and high-level boreholes, and there are a lot of cracks in the high-level boreholes before 12 m. The deviation distance of high-level borehole is large, and the actual vertical deviation of upper adjacent layer is small. Finally, the strategies to prevent the deviation of drilling construction are put forward. It includes four aspects: ensuring the reliability of drilling equipment, reasonably controlling the drilling length, standardizing the drilling, and reasonably selecting the drilling process parameters.

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A Case Study on the Gas Drainage Optimization Based on the Effective Borehole Spacing in Sima Coal Mine

Geofluids ◽

10.1155/2021/5510566 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Ming Ji ◽

Zhong-guang Sun ◽

Wei Sun

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Research Result ◽

Economic Benefits ◽

Coal Industry ◽

Gas Drainage ◽

Field Coupling ◽

Drainage Time ◽

Working Face

Based on the dynamic expressions of permeability and porosity of the coal seam derived in the paper, a multiphysical field coupling numerical model of gas migration under the interaction of stress field and seepage field was established. The gas drainage project #3 Coal Seam operated by Sima Coal Industry Co., Ltd., was selected as the study object. Taking different drainage time periods in various positions of drainage holes into consideration, combined with the advance situation of the 1207 working face in the Sima Coal Mine, a mixed layout gas drainage scheme featured with the effective borehole spacing was obtained through the COMSOL multiphysics simulation. In addition, a series of field industrial tests were performed to validate the research result, revealing that comprehensively considering the extraction time of coal and optimizing the layout of extraction boreholes can effectively improve the engineering economic benefits.

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Experimental Study on the Gas Flow Characteristics and Pressure Relief Gas Drainage Effect under Different Unloading Stress Paths

Geofluids ◽

10.1155/2020/8837962 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Chaolin Zhang ◽

Jiang Xu ◽

Enyuan Wang ◽

Shoujian Peng

Keyword(s):

Coal Seam ◽

Gas Flow ◽

Flow Characteristics ◽

Gas Production ◽

Gas Pressure ◽

Coal Seam Gas ◽

Pressure Relief ◽

Gas Drainage ◽

Coal Temperature ◽

Drainage Effect

Coal seam gas is a critical substance because it can be a source of a large quantity of clean energy as well as a dangerous source of risk. A pressure relief gas drainage is an effective and widely used method for coal seam gas recovery and gas disaster control in coal mines. A series of pressure relief gas drainage experiments were conducted using large-scale coal samples under different unloading stress paths in this study to explore the unloading stress paths. From the experimental results, the dynamic evolutions of gas pressure, coal temperature, and gas production were analyzed. The trends of gas pressure and coal temperature during pressure relief gas drainage were similar: dropping rapidly first and then slowly with time. Correspondingly, gas production was fast in the early stage of pressure relief gas drainage and became stable thereafter. Meanwhile, gas flow characteristics were significantly affected by the unloading stress paths. Gas pressure and coal temperature had the maximum descent by unloading stress in three directions simultaneously, and the unloading stress of the Z direction had the minimal impact when only unloading in one direction of stress. However, the influence of unloading stress paths on gas production was complex and time dependent. The difference coefficient parameter was proposed to characterize the influence degree of unloading stress paths on the pressure relief gas drainage effect. Eventually, the selection of unloading stress path under different situations was discussed based on time, which is expected to provide the basis for pressure relief gas drainage.

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Uneven stress and permeability variation of mining-disturbed coal seam for targeted CBM drainage: A case study in Baode coal mine, eastern Ordos Basin, China

Fuel ◽

10.1016/j.fuel.2020.119911 ◽

2021 ◽

Vol 289 ◽

pp. 119911

Author(s):

Chao Xu ◽

Gang Yang ◽

Kai Wang ◽

Qiang Fu

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Ordos Basin ◽

Permeability Variation

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Height of water-conducting fractured zone in a coal seam overlain by thin bedrock and thick clay layer: a case study from the Sanyuan coal mine in North China

Environmental Earth Sciences ◽

10.1007/s12665-020-8873-0 ◽

2020 ◽

Vol 79 (6) ◽

Author(s):

Hao Fan ◽

Lianguo Wang ◽

Yinlong Lu ◽

Zhaolin Li ◽

Wenshuai Li ◽

...

Keyword(s):

Coal Seam ◽

Coal Mine ◽

North China ◽

Clay Layer ◽

Fractured Zone ◽

Thin Bedrock

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Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.295-298.2980 ◽

2013 ◽

Vol 295-298 ◽

pp. 2980-2984

Author(s):

Xiang Qian Wang ◽

Da Fa Yin ◽

Zhao Ning Gao ◽

Qi Feng Zhao

Keyword(s):

Numerical Simulation ◽

Stress Distribution ◽

Coal Seam ◽

Coal Mine ◽

Abutment Pressure ◽

Surrounding Rock ◽

Geological Conditions ◽

Seam Mining

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.

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