scholarly journals A Novel Hydraulic Mode to Promote Gas Extraction: Pressure Relief Technologies for Tectonic Regions and Fracturing Technologies for Nontectonic Regions

2019 ◽  
Vol 9 (7) ◽  
pp. 1404 ◽  
Author(s):  
Shaojie Zuo ◽  
Zhaolong Ge ◽  
Zhe Zhou ◽  
Li Wang ◽  
Hanyun Zhao
Keyword(s):  
High Efficiency ◽  
Coal Mines ◽  
Clean Energy ◽  
Extraction Time ◽  
Efficient Production ◽  
Gas Extraction ◽  
Coal Seams ◽  
Pressure Relief ◽  
Gas Concentration ◽  
Coal Roadway

Extraction of gas (coalbed methane) produces clean energy and can ensure that coal mines maintain high-efficiency production. The currently available coal seam permeability enhancing technologies and modes have certain application restrictions. Therefore, a novel mode is proposed to promote gas extraction. This mode divides complex coal seams into tectonic regions and nontectonic regions based on geological structures. Then, the characteristics of different regions are matched with the advantages of different hydraulic technologies; thus, pressure relief technologies are proposed for tectonic regions, and fracturing technologies are proposed for nontectonic regions. The permeability of coal seams will be sharply increased without leaving unfractured areas. This mode will promote the effectiveness of gas extraction, shorten the extraction time, and ensure safe and efficient production in coal mines. A field application shows that this mode has a better effect than slotted directional hydraulic fracturing technology (SDHFT). The gas concentration and pure gas flow were increased by 47.1% (up to 24.94%) and 44.6% (up to 6.13 m3/min), respectively, compared to SDHFT over 9 months. The extraction time was reduced by 4 months. This mode reduced the number of times that gas concentration exceeded government standards during coal roadway excavation, and the coal roadway excavation speed was increased by 16% (up to 158 m/month).

scholarly journals Experimental Investigation on Mechanics and Seepage Characteristics of Tectonic and Intact Coal Containing Gas

2020 ◽  
Vol 10 (20) ◽  
pp. 7290
Author(s):  
Chaolin Zhang ◽  
Enyuan Wang ◽  
Jiang Xu ◽  
Shoujian Peng
Keyword(s):  
Coalbed Methane ◽  
Triaxial Compression ◽  
Coal Mines ◽  
Gas Pressure ◽  
Extraction Time ◽  
Gas Extraction ◽  
Effective Measure ◽  
Pressure Stage ◽  
Tectonic Coal ◽  
Seepage Characteristics

Coalbed methane is a double-edged sword with two attributes of energy and hazard in coal mines. Gas drainage is the most direct and effective measure for gas recovery and disaster prevention in coal mines, which is seriously affected by the mechanics and seepage characteristics of coal. In this work, we experimentally simulated the triaxial compression and gas depletion processes using both tectonic coal and intact coal. The mechanics and seepage characteristics of tectonic and intact coal under the coupling effect of stress and gas pressure were analyzed and compared. The results show that during the triaxial compression, the damage stress and peak stress of tectonic coal is only half that of intact coal, while their compaction stress or residual stress are almost the same. Meanwhile, the permeability recovery value after tectonic coal failure is very limited, even smaller than that of intact coal, although its primary permeability is much larger than that of intact coal. On the contrary, the permeability recovery value after intact coal failure is more than twice of its primary permeability. During the gas depletion, the rebound gas pressure of tectonic coal is smaller than that of intact coal, and the permeability of tectonic coal is one order of magnitude larger than that of intact coal before the gas pressure drops to 2 MPa. The broken of tectonic coal and the low permeability of intact coal may be the two principal reasons. Therefore, in the tectonic coal area, the gas extraction time at high gas pressure stage should be stabilized, while in the intact coal area, the gas extraction time at low gas pressure stage should be increased, and the coal permeability enhancement measures should be combined to achieve the goal of high and stable production of coalbed methane.

scholarly journals Pressure Relief by Blasting Roof Cutting in Close Seam Group Mining under Thick Sandstone to Enhance Gas Extraction for Mining Safety

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 603
Author(s):  
Kui Gao ◽  
Ping Huang ◽  
Ze-Gong Liu ◽  
Jian Liu ◽  
Fei Wang ◽  
...  
Keyword(s):  
Blast Hole ◽  
Thick Layer ◽  
Mine Pressure ◽  
Gas Extraction ◽  
Coal Face ◽  
Pressure Relief ◽  
Excessive Pressure ◽  
Gas Concentration ◽  
Mining Safety ◽  
High Level

Close seam group mining under thin immediate roofs and thick sandstone walls is typically performed with a strong mine pressure and gas concentration, which pose considerable risks to miners. In this study, the mechanism of pressure relief and permeability enhancement to enhance gas extraction for mining safety through blasting roof cutting were investigated through theoretical analyses, numerical simulations, and laboratory tests. The results revealed that, near the blast-hole, which produced numerous cracks, blasting disturbed the integrity of the thick-layer roofs and redistributed the stress near the blast-hole, which prevented violent mine pressure caused by excessive fracture distances on the thick and hard roofs, reduced the additional load on the support, increased vertical gas migration, and ameliorated the effect of gas drainage caused by high-level boreholes. The field applications of forced roof cutting through deep-hole blasting in the II 7224N face of the Renlou coal mine (Huaibei, Anhui, PR China) demonstrated that the occurrence of excessive pressure on the fully mechanized mining hydraulic support was prevented. The gas extraction volume of high-level boreholes was maintained at 6–8 m3/min; the extraction concentration was stable at approximately 35%; and the gas concentration in the upper corner of the coal face was lessened from 7% to <1%, which ensured normal mining in the coal face. The current results can provide data reference and a theoretical basis for roof management and gas control of the same type of coal face.

scholarly journals Case studies of comprehensive gas control method during fully mechanized caving of low permeability ultra-thick coal seams

2020 ◽  
Author(s):  
Bangyou Jiang ◽  
Shitan Gu ◽  
Yunliang Tan ◽  
Guangchao Zhang ◽  
Jihua Zhang
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
High Efficiency ◽  
Control Method ◽  
Measurement Data ◽  
Low Permeability ◽  
Coal Seams ◽  
Gas Concentration ◽  
High Position ◽  
Gas Control

Abstract Slicing fully mechanized caving mining now is a common high-efficiency mining method for ultra-thick coal seams. However, effective gas control has remained a difficulty in fully mechanized top-coal caving mining of low permeability ultra-thick coal seams. This study focused on mining of the #9-15 coal in Liuhuanggou Coal Mine, Xinjiang Province, China, and combined theoretical analyses and field test results for exploring comprehensive gas control methods for fully mechanized caving of low permeability ultra-thick coal seams. The No. (9-15)06 panel is a top slicing panel of the #9-15 coal with a mining height of 9 m, and the No. (4-5)02 goaf is located on the top of the panel. Through analysis, gas emissions in the No. (9-15)06 panel were mainly sourced from the coal wall, caving of top coal, goaf, and neighboring coal seams. A comprehensive gas control method based on source separation was proposed, which combined gas pre-drainage along the coal seam, high-position drilling on the top, pre-burial of pipes in the goaf, and pressure-balancing ventilation. Considering the poor gas pre-drainage effect for low permeability coal seams, the permeability of the coal seam was enhanced using hydraulic fracturing. According to coal seam and crustal stress distribution characteristics, the arrangement of the boreholes and backward segmented fracturing technology were designed. Field data show that coal underwent remarkable pre-fracturing under hydraulic fracturing. Mean gas pre-drainage from the boreholes was enhanced by nearly 4 times compared to the pre-hydraulic fracturing state. Finally, using the proposed comprehensive control method based on the gas sources, field tests were performed in the No. (9-15)06 panel. Field measurement data demonstrate that gas concentration in the return airflow fluctuated within a range of 0.05%~0.35%, i.e., gas concentration did not exceed the standard. The proposed gas control method can provide insightful reference for the other similar projects.

scholarly journals Experimental Study on Reasonable Spacing after Carbon Dioxide Presplitting in Low-Permeability Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zongyong Wei ◽  
Shugang Li ◽  
Haifei Lin ◽  
Botao Li ◽  
Yang Ding ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mines ◽  
Extraction Time ◽  
Shaanxi Province ◽  
Low Permeability ◽  
Efficient Production ◽  
Gas Drainage ◽  
Negative Exponential Function ◽  
Drainage Time ◽  
Drainage Radius

Gas disasters have been always a major hidden danger that affects mining safety in coal mines. Gas drainage by drilling is the fundamental method of gas control in coal mines. In view of the low-permeability coal seam, it is the basis of the safe and efficient production of the mine to take the measures of enhancing the permeability, improving the gas drainage efficiency, and shortening the drainage time. The 4−2 coal seam of the Jianxin coal mine in Shaanxi Province of China is a low-permeability coal seam. In order to obtain the reasonable hole spacing and the reasonable extraction time after the penetration enhancement, the pressure drop method is used to investigate the extraction radius. The results show that the gas pressure around the test hole decreases with time as a negative exponential function, and the effective radius of extraction increases with the increase of extraction time as a logarithmic function. Through the comparative analysis and variance analysis of the test data of the two drilling fields, it is proved that the data of the drainage radius of the two drilling fields are accurate and reliable. It is obtained that the reasonable spacing of the gas drainage holes is 8.10 m and the reasonable drainage time is 180 days after CO2 presplitting and permeability increase in the 4−2 coal seam of the mine.

Study on Underlying Coal and Strata Pressure-Relief Principle and the Gas Extraction Technique under Upper Protective Layer Mining

2014 ◽  
Vol 875-877 ◽  
pp. 1863-1870 ◽  
Author(s):  
Jian Liu ◽  
Jie Zhao ◽  
Ming Song Gao
Keyword(s):  
Rock Mass ◽  
Coal Seam ◽  
Protective Layer ◽  
Extraction Technique ◽  
Efficient Production ◽  
Gas Extraction ◽  
Pressure Relief ◽  
Fracture Development ◽  
Floor Heave ◽  
Coal Rock

By study on underlying coal and strata pressure-relief principle and the gas extraction technique under upper protective layer mining, we obtain the stress change and distribution law of underlying coal-rock mass. We analyze the deformation law and fracture development characteristics of underlying coal-rock mass movement. With mining proceeding ahead, the total floor coal and rock experiences compression deformation first, then expansion deformation and re-compaction of the continuous periodic destruction. Based on different development characteristics and status of underlying coal-rock mass, the underlying coal-rock mass under an effect of upper protective layer mining was divided into the floor heave fracture zone and the floor heave deformation zone in this paper. The permeability coefficient of change law of underlying the coal seam as follows: the original value-small decreasing-increasing greatly-reducing-stability at last. The field test for upper protective layer mining of Zhang-ji coal mine of Huainan shows that the effect of pressure relief of protected seam is very good. So it eliminates the risk of gas outburst, ensuring safety mining of the protected seam. The research has an important significance for safety and efficient production under similar exploitation conditions of low-permeability with high gas and outburst risk coal seam.

scholarly journals Design and Implementation of a Coalbed Methane Extraction Device Using Microwave Radiation

2021 ◽  
Author(s):  
Ali Jebelli ◽  
Arezoo Mahabadi ◽  
Rafiq Ahmad
Keyword(s):  
Coal Mining ◽  
Microwave Radiation ◽  
Coalbed Methane ◽  
Global Economy ◽  
Coal Mines ◽  
Clean Energy ◽  
Potential Hazard ◽  
Coal Seams ◽  
Continuous Growth ◽  
Methane Gas

Abstract The continuous growth of the population and the global economy increases the need for sustainable energy. To this end, the recovery factor of hydrocarbon resources in the world should be maximized. One of the main sources of natural gas is coalbed methane, a gas accumulated in pores inside coal. On the other hand, methane gas explosion is a potential hazard in coal mines, which causes many casualties every year in coal mines worldwide. Mine ventilation alone cannot create a safe environment for coal mining due to the high volume of gas released in some coal seams. Therefore, Methane gas extraction can turn one of the major hazards in coal mining into a clean energy source and have dual benefits. Unfortunately, the permeability of most coal seams is very low, and this low permeability limits the development and production of commercial coalbed methane. Therefore, coalbed methane reservoir stimulation is an attractive option because the relative permeability of natural fractures in the coal seam and the surrounding rock greatly affects the amount of extractable gas. Microwave radiation is one of the new methods to increase the permeability of coal. In this research, we design, simulate and implement a small, lightweight, portable microwave gun that uses a conical horn with an aperture of 28 cm with a working frequency of 2.45 GHz to evaporate the moisture in the circle with a diameter of 40 cm from a coal wall and increases the permeability of the wall due to microwave radiation. Because in previous studies, the tests were performed only on large and small capacity devices without any control over the amount of microwave radiation and by replacing the gas inside the chamber with argon or nitrogen gases, which does not represent the real conditions in the mines. Therefore, by building a small device, we have overcome the limit of coal size and amount. By considering the coal ignition temperature, we have provided the challenges related to removing oxygen from the air and the possibility of working in real conditions in mines with larger volumes of coal, which is very similar to the mining environment. Also, the proposed small and portable device in this paper allows us to use it in different environments.

Evaluating pressure-relief mining performances based on surface gas venthole extraction data in longwall coal mines

2015 ◽  
Vol 24 ◽  
pp. 431-440 ◽  
Author(s):  
Cun Zhang ◽  
Shihao Tu ◽  
Qingsheng Bai ◽  
Guanyu Yang ◽  
Lei Zhang
Keyword(s):  
Coal Mines ◽  
Pressure Relief

A study on source identification of gas explosion in coal mines based on gas concentration

Fuel ◽  
2021 ◽  
Vol 290 ◽  
pp. 120053
Author(s):  
Baiwei Lei ◽  
Chenguang Zhao ◽  
Binbin He ◽  
Bing Wu
Keyword(s):  
Source Identification ◽  
Coal Mines ◽  
Gas Explosion ◽  
Gas Concentration

scholarly journals Stability Control of Deep Coal Roadway under the Pressure Relief Effect of Adjacent Roadway with Large Deformation: A Case Study

2021 ◽  
Vol 13 (8) ◽  
pp. 4412
Author(s):  
Houqiang Yang ◽  
Nong Zhang ◽  
Changliang Han ◽  
Changlun Sun ◽  
Guanghui Song ◽  
...  
Keyword(s):  
Large Deformation ◽  
Coal Mine ◽  
High Stress ◽  
Surrounding Rock ◽  
Western China ◽  
Engineering Practice ◽  
Pressure Relief ◽  
Coal Roadway ◽  
And Control ◽  
Relief Effect

High-efficiency maintenance and control of the deep coal roadway surrounding rock stability is a reliable guarantee for sustainable development of a coal mine. However, it is difficult to control the stability of a roadway that locates near a roadway with large deformation. With return air roadway 21201 (RAR 21201) in Hulusu coal mine as the research background, in situ investigation, theoretical analysis, numerical simulation, and engineering practice were carried out to study pressure relief effect on the surrounding rock after the severe deformation of the roadway. Besides, the feasibility of excavating a new roadway near this damaged one by means of pressure relief effect is also discussed. Results showed that after the strong mining roadway suffered huge loose deformation, the space inside shrank so violently that surrounding rock released high stress to a large extent, which formed certain pressure relief effect on the rock. Through excavating a new roadway near this deformed one, the new roadway could obtain a relative low stress environment with the help of the pressure relief effect, which is beneficial for maintenance and control of itself. Equal row spacing double-bearing ring support technology is proposed and carried out. Engineering practice indicates that the new excavated roadway escaped from possible separation fracture in the roof anchoring range, and the surrounding rock deformation of the new roadway is well controlled, which verifies the pressure relief effect mentioned. This paper provides a reference for scientific mining under the condition of deep buried and high stress mining in western China.

Sign in / Sign up

Export Citation Format

Share Document