Journal articles on the topic 'Deep coal gas'
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1
Yang, Li, Xin Fang, Xue Wang, Shanshan Li, and Junqi Zhu. "Risk Prediction of Coal and Gas Outburst in Deep Coal Mines Based on the SAPSO-ELM Algorithm." International Journal of Environmental Research and Public Health 19, no. 19 (September 28, 2022): 12382. http://dx.doi.org/10.3390/ijerph191912382.
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Effective risk prevention and management in deep coal mines can reduce the occurrences of outburst accidents and casualties. To address the low accuracy and inefficiency of coal–gas outburst prediction in deep coal mines, this study proposes a deep coal–gas outburst risk prediction method based on kernal principal component analysis (KPCA) and an improved extreme learning machine (SAPSO-ELM) algorithm. Firstly, high-dimensional nonlinear raw data were processed by KPCA. Secondly, the extracted sequence of outburst-causing indicator principal components were used as the input variables for the simulated annealing particle swarm algorithm (SAPSO), which was proposed to optimize the input layer weights and implied layer thresholds of the ELM. Finally, a coal and gas outburst risk prediction model for a deep coal mine based on the SAPSO-ELM algorithm was developed. The research results show that, compared with the ELM and PSO-ELM algorithms, the SAPSO-ELM optimization algorithm significantly improved the accuracy of risk prediction for coal–gas outbursts in deep coal mines, and the accuracy rate was as high as 100%. This study enriches the theory and methods of safety management in deep coal mines, and effectively helps coal mine enterprises in improving their ability to manage coal–gas outburst risks.
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Fan, Chaojun, Haiou Wen, Sheng Li, Gang Bai, and Lijun Zhou. "Coal Seam Gas Extraction by Integrated Drillings and Punchings from the Floor Roadway considering Hydraulic-Mechanical Coupling Effect." Geofluids 2022 (January 7, 2022): 1–10. http://dx.doi.org/10.1155/2022/5198227.
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Owing to the exhaustion of shallow coal resources, deep mining has been occupied in coal mines. Deep buried coal seams are featured by the great ground stress, high gas pressure, and low permeability, which boost the risk of gas disasters and thus dramatically threaten the security about coal mines. Coal seam gas pressure and gas content can be decreased by gas extraction, which is the primary measure to prevent and control mine gas disasters. The coal mass is simplified into a continuous medium with dual structure of pores and fractures and single permeability. In consideration of the combined effects of gas slippage and two-phase flow, a hydraulic-mechanical coupling model for gas migration in coals is proposed. This model involves the equations of gas sorption and diffusion, gas and water seepage, coal deformation, and evolution of porosity and permeability. Based on these, the procedure of gas extraction through the floor roadway combined with hydraulic punching and ordinary drainage holes was simulated, and the gas extraction results were used to evaluate the outburst danger of roadway excavation and to verify the engineering practice. Results show that gas extraction can reduce coal seam gas pressure and slow down the rate of gas release, and the established hydraulic-mechanical coupling model can accurately reveal the law of gas extraction by drilling and punching boreholes. After adopting the gas extraction technology of drilling and hydraulic punching from the floor roadway, the remaining gas pressure and gas content are reduced to lower than 0.5 MPa and 5.68 m3/t, respectively. The achievements set a theoretical foundation to the application of drilling and punching integrated technology to enhance gas extraction.
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Geng, Mei Hua, Xiu Jiang Lv, and Xiao Gang Zhang. "The Structural Analysis of Deep Gas Occurrence and Prevention of Gas Disaster in Fengfeng Coalfield." Advanced Materials Research 734-737 (August 2013): 484–87. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.484.
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The geological structure is an important factor of gas occurrence in coal seam, and the gas occurrence in deep coal seam should be paid attention to enough because the occurrence was more controlled by geological structure and influence. Taken Fengfeng coalfield as target in this paper, the geological structure of this coalfield was described. The deep coal mining district which is monoclinic structure in Fengfeng is located in the east of Gushan anticlinoria, which the junior small anticlines and synclines of the sub-echelon are well developed. And regional fault structures are intensive, the pressure structure is the major structure among this region. The characteristics of geological structure in Fengfeng coalfield were analyzed. The tensional structure planes and pressure structure are the major effect factors, and the latter is the main form of gas occurrence in deep. Some suggestions on safe of deep mining in high gas environment is also put forward, in order to provide theoretical support for the deep coal mining and gas disaster prevention.
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Yin, Zhiqiang, Zhiyu Chen, Jucai Chang, Zuxiang Hu, Haifeng Ma, and Ruimin Feng. "Crack Initiation Characteristics of Gas-Containing Coal under Gas Pressures." Geofluids 2019 (February 7, 2019): 1–12. http://dx.doi.org/10.1155/2019/5387907.
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In deep coal mines, coal before the working face is subjected to coupled high mining-induced stress and gas pressure. Such condition may facilitate crack formation and propagation in the coal seam, leading to serious coal and gas disasters. In this study, the mechanical properties (i.e., uniaxial compressive strength, tensile strength, and fracture toughness) of gas-containing coal with four levels of initial gas pressure (i.e., 0.0, 0.5, 1.0, and 1.5 MPa) were investigated by uniaxial compression, Brazilian disc, and notched semicircular bending loading test. A newly developed gas-sealing device and an RMT-150 rock mechanics testing machine were used. Fracture modes under different initial gas pressures were also determined. A theoretical method of fracture mechanics was used to analyze crack initiation characteristics under gas adsorption state. Results show that the uniaxial compressive strength, tensile strength, and fracture toughness of gas-containing coal decreased with increasing initial gas pressure. The tensional fracture occurred in gas-containing coal under uniaxial compressive loading with high gas pressure. Cracks in gas-containing coal propagated under small external loads due to the increase in effective stress of crack tip and decrease in cracking strength. This study provided evidence for modifications of the support design of working face in deep coal mines. Furthermore, the correlations between fracture toughness, compressive strength, and tensile strength of gas-containing coal were investigated.
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Sun, Haitao, Linchao Dai, Jun Lu, Jie Cao, and Minghui Li. "Analyzing Energy Transfer Mechanism during Coal and Gas Protrusion in Deep Mines." Processes 10, no. 12 (December 8, 2022): 2634. http://dx.doi.org/10.3390/pr10122634.
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Coal is the mainstay of China’s energy supply. With the gradual progress in China’s policy of phasing out backward coal production capacity, the intensive and deep mining of coal has gradually become the new norm. The current mining depth is increasing at a rate of 10~15 m/year. The high crust stress, high gas pressure, high ground temperature, and engineering disturbance stress in deep coal mines can lead to the occurrence of coal–rock–gas dynamic disasters that are complex and show the characteristics of compound dynamic disasters. It is important to understand the evolution and mechanism of deep coal and rock dynamic disasters accurately for the safe development of deep resources. To study the mechanism of occurrence and the evolution of impact–protrusion compound dynamic disasters, we herein analyzed the apparent characteristics of coal–rock–gas compound dynamic disasters in deep mines and obtained the mechanical and acoustic emission characteristics of coal–rock composites through indoor experiments. Then, we conducted in-depth analysis on the non-uniform deformation behaviors and non-uniform stress field of the coal–rock composite and clarified the generation mechanism of local tensile cracks at the coal–rock interface. Subsequently, we established the energy transfer model of the rock–rock–gas composite specimen in the process of dynamic destabilization in the engineering scale mining field and revealed the mechanism of nonlinear energy evolution and release of the coal–rock–gas composite, which has been less reported in previous studies. In this paper, we further clarified the occurrence and development mechanism of coal–rock–gas compound dynamic disasters in the engineering scale mining environment to guide the prevention and control of coal–rock–gas dynamic disasters in deep mines.
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Sun, Yingfeng, Qingxia Lin, Shuaipeng Zhu, Chujian Han, Xiaoliang Wang, and Yixin Zhao. "NMR investigation on gas desorption characteristics in CBM recovery during dewatering in deep and shallow coals." Journal of Geophysics and Engineering 20, no. 1 (January 18, 2023): 12–20. http://dx.doi.org/10.1093/jge/gxac090.
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Abstract Coalbed methane (CBM) development requires dewatering until the reservoir pressure is less than the critical desorption pressure. Significant quantities of CBM in China are buried >1000 m deep. Therefore, the desorption characteristics of deep CBM reservoirs must be investigated for the further development of deep CBM. In this study, the variation laws of adsorbed and free CH4 during adsorption in dry samples and during desorption via dewatering are investigated using nuclear magnetic resonance. During CH4 adsorption in dry samples by increasing CH4 pressure and during CH4 desorption in water-injected samples by dewatering, a Langmuir relationship exists between the volume of adsorbed CH4 and the pressure in deep and shallow coals, and the volume of free CH4 and the pressure are linearly related. When the pressure is the same, the volume of adsorbed CH4 in the dry coal samples during adsorption is larger than that in the water-injected samples during desorption by dewatering. When the pressure is the same, for the difference in the adsorbed CH4 volume between adsorption and desorption isotherms, shallow coal is less significant than deep coal. The slopes of free CH4 in deep coal are lower than those in shallow coal during adsorption and desorption.
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Shasha, Si, Wang Zhaofeng, Zhang Wenhao, and Dai Juhua. "Study on Adsorption Model of Deep Coking Coal Based on Adsorption Potential Theory." Adsorption Science & Technology 2022 (August 8, 2022): 1–13. http://dx.doi.org/10.1155/2022/9596874.
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With the exhaustion of coal resources in shallow coal seams, many mining areas have moved to deep mining, and the coal storage environment is obviously affected by the mining depth, mainly manifested as the increase of gas pressure and temperature, which makes the adsorption characteristics of deep coal seam gas much more complicated than shallow coal seam. Based on this, this paper chooses Pingdingshan coking coal as the research object, using Hsorb-2600 high-temperature and high-pressure gas adsorption instrument to carry on isothermal adsorption experiment. According to the adsorption theory and the uniqueness of the adsorption characteristics cure, the adsorption model was analyzed and studied. The results show that the predicted curve of coal seam gas adsorption isotherm is in good agreement with the measured curve, the relative error is less than 10%, and the adsorption characteristic curve is logarithmic. At the same time, the model is used to study the variation of adsorbed gas amount with mining depth. The results show that the adsorbed gas amount increases first and then decreases with coal burial depth.
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Zhao, Zhi Gen, Jia Chen, and Jia Ping Yan. "Features of Jianshanchong Klippe and its Control to Gas Geology at Qingshan Coal Mine, Jiangxi Province." Applied Mechanics and Materials 164 (April 2012): 501–5. http://dx.doi.org/10.4028/www.scientific.net/amm.164.501.
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The coal and gas outburst is serious at Qingshan Coal Mine of Jiangxi Province, so it is of significance to research the features of Jianshanchong klippe and its control to gas geology. The research reveals that: Jianshanchong klippe is distributed from the east boundary of Qingshan Coal Mine to No. 45 Exploration Line, its transverse profile is like a funnel while its longitudinal profile is like a wedge, northwest side of the klippe is thicker and deeper while southeast side is thinner and more shallow. Because of the cover and insert of Jianshanchong klippe, the structure of coal-bearing strata is more complex, some secondary folds are formed, and also, the coal seam is changed greatly, the tectonic coal is well developed and the coal seam is suddenly thickening or thinning. Due to the effect of Jianshanchong klippe, the coal and gas outbursts occur in the area of secondary folds, thicker coal seams or tectonic coals. Concerning the prediction of gas geology in deep area, in view of the facts including simpler structure, stable coal seam and decreased thickness, the gas emission rate and the coal and gas outburst will decrease in Fifth and Sixth Mining Level than that in Second and Third Mining Level
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Zhu, Junqi, Li Yang, Xue Wang, Haotian Zheng, Mengdi Gu, Shanshan Li, and Xin Fang. "Risk Assessment of Deep Coal and Gas Outbursts Based on IQPSO-SVM." International Journal of Environmental Research and Public Health 19, no. 19 (October 8, 2022): 12869. http://dx.doi.org/10.3390/ijerph191912869.
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Coal and gas outbursts seriously threaten the mining safety of deep coal mines. The evaluation of the risk grade of these events can effectively prevent the occurrence of safety accidents in deep coal mines. Characterized as a high-dimensional, nonlinear, and small-sample problem, a risk evaluation method for deep coal and gas outbursts based on an improved quantum particle swarm optimization support vector machine (IQPSO-SVM) was constructed by leveraging the unique advantages of a support vector machine (SVM) in solving small-sample, high-dimension, and nonlinear problems. Improved quantum particle swarm optimization (IQPSO) is used to optimize the penalty and kernel function parameters of SVM, which can solve the optimal local risk and premature convergence problems of particle swarm optimization (PSO) and quantum particle swarm optimization (QPSO) in the training process. The proposed algorithm can also balance the relationship between the global search and local search in the algorithm design to improve the parallelism, stability, robustness, global optimum, and model generalization ability of data fitting. The experimental results prove that, compared with the test results of the standard SVM, particle swarm optimization support vector machine (PSO-SVM), and quantum particle swarm optimization support vector machine (QPSO-SVM) models, IQPSO-SVM significantly improves the risk assessment accuracy of coal and gas outbursts in deep coal mines. Therefore, this study provides a new idea for the prevention of deep coal and gas outburst accidents based on risk prediction and also provides an essential reference for the scientific evaluation of other high-dimensional and nonlinear problems in other fields. This study can also provide a theoretical basis for preventing coal and gas outburst accidents in deep coal mines and help coal mining enterprises improve their safety management ability.
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Jiang, Guo Ping. "The Studies on Gas-Bearing Characteristics of Deep Coal Seams in Yanchang Oil and Gas Province, China." Advanced Materials Research 962-965 (June 2014): 213–16. http://dx.doi.org/10.4028/www.scientific.net/amr.962-965.213.
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In this paper, four general directions are described to make evaluations and their resource potential; those are coal structure and coal level, gas content of deep coalbed, the coalbed thickness and distribution and the buried depth of coalbed. Coalfields of the study area are mainly Permian and Carboniferous coal seam of Shanxi Formation coal and Benxi group 11 # coal, coal seam depth 1370-1812m. No. 3 coal-seam average layer thickness of 1.6 m, the monolayer most 2 m thick; No. 11 coal-seam in the average layer thickness of 3 m, single-layer thickness of 4.5 m. Predict the amount of coal resources of 17.3 one hundred million t. Predict coal-bed methane resources of 27.68 billion cubic reserve abundance of 104 million square / km2 in. The exploration results show that this region has good development prospects.
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Menpes, Sandra, and Tony Hill. "Emerging continuous gas plays in the Cooper Basin, South Australia." APPEA Journal 52, no. 2 (2012): 671. http://dx.doi.org/10.1071/aj11085.
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Recent off-structure drilling in the Nappamerri Trough has confirmed the presence of gas saturation through most of the Permian succession, including the Roseneath and Murteree shales. Basin-centred gas, shale gas and deep CSG plays in the Cooper Basin are now the focus of an escalating drilling and evaluation campaign. The Permian succession in the Nappamerri Trough is up to 1,000 m thick, comprising very thermally mature, gas-prone source rocks with interbedded sands—ideal for the creation of a basin-centred gas accumulation. Excluding the Murteree and Roseneath shales, the succession comprises up to 45% carbonaceous and silty shales and thin coals deposited in flood plain, lacustrine and coal swamp environments. The Early Permian Murteree and Roseneath shales are thick, generally flat lying, and laterally extensive, comprising siltstones and mudstones deposited in large and relatively deep freshwater lakes. Total organic carbon values average 3.9% in the Roseneath Shale and 2.4% in the Murteree Shale. The shales lie in the wet gas window (0.95–1.7% Ro) or dry gas window (>1.7% Ro) over much of the Cooper Basin. Thick Permian coals in the deepest parts of the Patchawarra Trough and over the Moomba high on the margin of the Nappamerri Trough are targets for deep CSG. Gas desorption analysis of a thick Patchawarra coal seam returned excellent total raw gas results averaging 21.2 scc/g (680 scf/ton) across 10 m. Scanning electron microscopy has shown that the coals contain significant microporosity.
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Zhou, Aitao, Kai Wang, Lingpeng Fan, and T. A. Kiryaeva. "Gas-solid coupling laws for deep high-gas coal seams." International Journal of Mining Science and Technology 27, no. 4 (July 2017): 675–79. http://dx.doi.org/10.1016/j.ijmst.2017.05.016.
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Feng, Cai. "Big Diameter and Long Drilling-Holes Technology and its Application in Drainage Gas in Dingji Coal Mine." Advanced Materials Research 354-355 (October 2011): 104–8. http://dx.doi.org/10.4028/www.scientific.net/amr.354-355.104.
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Taking advantage of the method of big diameter and long drilling-holes in coal seam’ roof instead of roadway method to drainage gas from coal seam, aimed at the condition of deep coal seam and high risk of outburst in Dingji Coal Mine. The amount and rate of drainage gas was increased, and decreased the time and engineering amount of drainage gas, and effectively diminished the risk of outburst of coal and gas. And a new approach adapt to Dingji Coal Mine to drainage gas is acquired.
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Gao, Yanan, Feng Gao, Guanghui Dong, Weicheng Yan, and Xiaojun Yang. "The mechanical properties and fractal characteristics of the coal under temperature-gas-confining pressure." Thermal Science 23, Suppl. 3 (2019): 789–98. http://dx.doi.org/10.2298/tsci180610094g.
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Deep mining is the most important way to obtain the resource in China now. Thus, rock is the main objective that the deep mining will encounter. Meanwhile, the frequent catastrophes in deep mining such as rock burst, coal and gas bursts, roof caving, water bursts, is the most serious problem. To have a better understanding of the mechanisms of fracture and the laws of damage evolution of rock and coal under deep environment, in this paper, the micro- and meso-scale method is employed to study the behavior of coal under different temperature, confining pressure and gas pressure. Then, the significance of the effect of temperature, confining pressure, and gas pressure on mechanical parameters is analyzed by using the ANOVA method. The fractal study of coal failure pattern by employing the SEM test and fractal dimension was carried out. The fractal dimension of coal fractures was calculated by using the box-covering method. Then, the effects of all factors on the fractal dimension of coal fractures were analyzed.
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Zhang, Jianguo, Man Wang, and Yingwei Wang. "Fracture evolution and gas transport laws of coal and rock in one kilometer deep coal mine with complicated conditions." Thermal Science 23, Suppl. 3 (2019): 907–15. http://dx.doi.org/10.2298/tsci180526126z.
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As coal mining gradually extends deeper, coal seams in China generally show high stress, high gas pressure and low permeability, bringing more difficulty to coal mining. Therefore, in order to strengthen gas extraction, it is necessary to carry out reservoir reconstruction after deep coal seams reached. In this paper, the distribution and evolution laws of fracture zone overlaying strata of J15 seam in Pingdingshan No. 10 coal mine after excavation were studied by combining similar simulation and numerical simulation, meanwhile, the gas transport law within fracture zone was numerically simulated. The results show that the fracture zone reaches a maximum of 350 mm in the vertical direction and is 75 mm away from W9,10 coal seams in vertical distance. Since W9,10 coal seams are in an area greatly affected by the bending zone of J15 coal seam under the influence of mining, the mining of J15 coal seam will exert a strong permeability enhancement effect on W9,10 coal seams. The J15 coal seam can act as a long-distance protective layer of W9,10 coal seams to eliminate the outburst danger of the long-distance coal seams in bending zone with coal and gas outburst danger, thereby achiev?ing safe, productive and efficient integrated mining of coal and gas resources. The gas flux of mining-induced fractures in the trapezoidal stage of mining-induced fracture field is far greater than that in the overlaying stratum matrix. The horizontal separation fractures and vertical broken fractures within the mining-induced fracture field act as passages for gas-flow. Compared with gas transport in the overlaying stratum matrix, the horizontal separation fractures and vertical broken fractures within the mining-induced fracture field play a role in guiding gas-flow. The research results can provide theoretical support for the arrangement of high-level gas extraction boreholes in roof fracture zones.
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Nie, Fengxiang, Honglei Wang, and Liming Qiu. "Research on the Disaster-Inducing Mechanism of Coal-Gas Outburst." Advances in Civil Engineering 2020 (March 29, 2020): 1–12. http://dx.doi.org/10.1155/2020/1052618.
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In China, coal-gas outburst is seriously affecting safety of the coal mine. To improve the safety status of underground coal mining, this work investigated the evolution process and occurrence mechanism of coal-gas outburst under the coupling action of stress and gas. Results show that increasing either gas pressure or in-situ stress can make coal destroy and destabilize, and the contribution of gas pressure to coal failure is twice that of in-situ stress. In ultradeep coal mining, coal-gas outburst may occur even under the condition of low gas pressure due to large in-situ stress. Moreover, the larger the mining depth is, the lower the gas index is required for disaster occurrence. The results have certain guiding significance for coal energy mining and the control of coal-gas outburst in deep coal mining.
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Zhang, Zhiwei, Yang Liu, Lei Wang, Xuhui Xia, and Zelin Zhang. "Deep learning-based image classification of gas coal." International Journal of Global Energy Issues 43, no. 4 (2021): 371. http://dx.doi.org/10.1504/ijgei.2021.10040101.
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Zhang, Zelin, Zhiwei Zhang, Yang Liu, Lei Wang, and Xuhui Xia. "Deep learning-based image classification of gas coal." International Journal of Global Energy Issues 43, no. 4 (2021): 371. http://dx.doi.org/10.1504/ijgei.2021.117027.
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Teng, Juan, Yan Bin Yao, Da Meng Liu, Zhi Qiang Liu, and Bei Liu. "Identification of Coal Petrologic-Structure by Using Geophysical Logging Data: A Case Study of the Coals of Hancheng Coalbed Methane Field." Applied Mechanics and Materials 316-317 (April 2013): 795–98. http://dx.doi.org/10.4028/www.scientific.net/amm.316-317.795.
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Coal petrologic structure is important for the prediction of coal and the associated coalbed methane outburst during coal mining. This paper discusses the relationship between the response characteristics of natural gamma (GR), laterlog deep (LLD) and compensation density curve (RHOB), and the coal structures. Results show that the tectonic-coals (the coals with high breakage degree by tectonic structures) can be identified by the logging characteristics of low amplitude of GR (20-90 API), high amplitude of LLD (300-1800 Ωm), and low amplitude of RHOB (1.25-1.5g/cm3). It was found that with increasing degree of the breakage, coal pores and fractures become well developed, and thus reduce the bulk density of coal and the content of radioelement but more gas within the coal. This is the reason for logging performances of low amplitude of GR and RHOB, as well as high amplitude of LLD for the tectonic-coals.
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Zhao, Dan, Mingyu Wang, and Xinhao Gao. "Study on the Technology of Enhancing Permeability by Millisecond Blasting in Sanyuan Coal Mine." Mathematical Problems in Engineering 2021 (September 28, 2021): 1–12. http://dx.doi.org/10.1155/2021/8247382.
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To reduce gas disasters in low permeability and high-gas coal seams and improve gas predrainage efficiency, conventional deep-hole presplitting blasting permeability increasing technology was refined and perfected. The numerical calculation model of presplitting blasting was established by using ANSYS/LS-DYNA numerical simulation software. The damage degree of coal and rock blasting was quantitatively evaluated by using the value range of the damage variable D. According to the actual field test parameters of coal seam #3 in the Sanyuan coal mine, Dlim = 0.81–1.0 was the coal rock crushing area, Dlim = 0.19–0.81 was the coal rock crack area, and Dlim = 0–0.19 was the coal rock disturbance area. By comparing and analysing the damage distribution nephogram of coal and rock mass under the influence of different millisecond blasting time interval and the blasting effect of simulation model, the optimal layout parameters of multilayer through cracks were obtained theoretically. And, the determined parameters were tested on the working face of the 1312 transportation roadway in coal seam #3 of the Sanyuan coal mine. The permeability effect was compared and analysed through the analysis of the gas concentration, gas purity, and mixing volume before and after the implementation of deep-hole presplitting blasting antireflection technology, as well as the change of gas pressure, attenuation coefficient, permeability coefficient, and other parameters between blasting coal seams. The positive role of millisecond blasting in reducing pressure and increasing permeability in low permeability and high-gas coal seam were determined.
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Dunlop, Erik C. "A new concept for the extraction of gas from Permian ultra-deep coal seams of the Cooper Basin, Australia: Expanding Reservoir Boundary Theory." APPEA Journal 60, no. 1 (2020): 296. http://dx.doi.org/10.1071/aj19011.
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An alternative geomechanical reservoir boundary condition is proposed for ultra-deep coal seams of the Cooper Basin in central Australia. This new concept is embodied within the author’s ‘Expanding Reservoir Boundary (ERB) Theory’, which calls for a paradigm shift in gas extraction technology, diametrically opposed to current practices. As with shale, full-cycle, standalone commercial gas production from Cooper Basin ultra-deep coal seams requires a large stimulated reservoir volume (SRV) having high fracture surface area for gas desorption. This goal has not yet been achieved after 13 years of trials because, owing to the bipolar combination of shale-like reservoir properties and coal-like geomechanical properties, these poorly cleated, inertinitic coal seams exhibit ‘hybrid’ characteristics. Stimulation techniques adopted from other play types are incompatible with the highly unfavourable combination of nanoDarcy-scale permeability, ‘ductility’ and high stress. Nevertheless, gas flow potential counterintuitively increases with depth, contingent upon the creation of an effective SRV. Optimum reservoir conditions occur at depths beyond 9000 feet (2740 m), driven by dehydration, high gas content, gas oversaturation, overpressure and a rigid host rock framework. The physical response of ultra-deep coal seams and the surrounding host rock to pressure drawdown is inadequately characterised. It remains to be established how artificial fracture and coal fabric aperture width change due to the competition between desorption-induced coal matrix shrinkage and compaction caused by increasing effective stress. Studies by the author suggest that pressure arching may ultimately control gas extraction efficiency. Harnessing this geomechanical phenomenon could resolve the technical impasse that currently inhibits commercialisation. Pressure arching neutralises SRV compaction by deflecting stress to adjacent strata of greater integrity. These strata then function as an abutment for accommodating increased stress outside the SRV. This shielding effect allows producing ultra-deep coal seams to progressively de-stress and ‘self-fracture’ naturally, in an overall state of shrinkage-induced tensile failure. An ‘expanding reservoir boundary and decreasing confining stress’ condition is generated by the combined, mutually sustaining actions of coal matrix shrinkage and sympathetic pressure arch evolution. This causes the SRV to steadily increase in size and permeability. Cooper Basin ultra-deep coal seams may be effectively stimulated by harnessing this self-perpetuating, depth-resistant mechanism for creating permeability and surface area. The ultra-deep coal seams may be induced to pervasively ‘shatter’ or ‘self-fracture’ naturally during production, independent of ‘brittleness’, analogous to the manner in which shrinkage crack networks slowly form, in a state of intrinsic tension, within desiccating clay-rich surface sediment.
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Zhao, Sheng Shan, Wei Dong Pan, Xin Wang, and Jia Dun Liu. "Prediction Technology of Coal and Gas Outburst in Xuandong Coal Mine." Advanced Materials Research 255-260 (May 2011): 3731–34. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.3731.
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Based on the complicated geological conditions of coal seam in Xuandong Coal Mine, such as deep burial depth, high gas content, magmatic rock intrusion and so on, the distribution regularities of magmatic rock, gas and geological structures were analyzed and studied. Combining with the practical situation of the dynamic disaster and phenomenon during the mining, the dangerous zones of coal and gas outburst were predicted and regional divided. The research results would have certain significance of practical guide to the outburst prevention and disaster reduction.
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Qiu, Dandan, Yanling Wu, and Li Li. "Evaluation of the Gas Drainage Effect in Deep Loose Coal Seams Based on the Cloud Model." Sustainability 14, no. 19 (September 29, 2022): 12418. http://dx.doi.org/10.3390/su141912418.
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The gas drainage effect is one of the important elements in the study of gas drainage in coal mines. It is critical to establish an effective evaluation model of the gas drainage effect for coal mines because the result of gas drainage is directly related to the safety of the coal mines. Through the research related to the safety evaluation in the existing coal mining process, we discovered that there are few studies on the evaluation of the impact of deep and soft gas drainage, and the evaluation methods are not sufficiently effective to resolve the complex problems arising in the process of gas drainage. This paper took “three soft” coal seams in the Lugou Coal Mine as the research object and constructed the evaluation index system on the basis of thoroughly analyzing the factors of coal seam drainage. We then employed a combination weighting method to attain the optimal weight by organically integrating the Analysis Hierarchical Process subjective weighting method and the Criteria Importance Through Interaction Correlation objective weighting method and utilized the cloud model to compute the numerical characteristic value of the evaluation index. In the end, this method obtained an evaluation result of the gas drainage effect evaluation. The evaluation result grade is good. Additional analysis was performed according to the evaluation factors, and corresponding improvement measures were proposed. This is of great importance in promoting safe production and improving the efficiency of gas drainage.
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Zhang, Lei, Chen Jing, Shugang Li, Ruoyu Bao, and Tianjun Zhang. "Seepage Law of Nearly Flat Coal Seam Based on Three-Dimensional Structure of Borehole and the Deep Soft Rock Roadway Intersection." Energies 15, no. 14 (July 8, 2022): 5012. http://dx.doi.org/10.3390/en15145012.
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Exploring the evolution characteristics of gas seepage between boreholes during the drainage process is critical for the borehole’s layout and high-efficiency gas drainage. Based on the dual-porous medium assumption and considering the effect of stress redistribution on coal seam gas seepage characteristics, a coal seam gas seepage model with a three-dimensional roadway and borehole crossing structure has been established and numerically calculated, concluding that the coal seam is between the drainage boreholes. The temporal and spatial evolution characteristics of gas pressure and permeability help elucidate the gas seepage law of the nearly flat coal seam associated with the deep soft rock roadway and borehole intersection model. The results indicate that: (1) The roadway excavation results in localized stress in some areas of the surrounding rock, reducing the strength of the coal body, increasing the expansion stress, and increasing the adsorption of gas by the coal body. (2) Along the direction of the coal seam, the permeability decreases initially and then increases. The gas pressure in the coal seam area in the middle of the borehole is higher than the pressure in the coal seam around the borehole, and the expansion stress and deformation increase, reducing the permeability of the coal body; when near the next borehole, the greater the negative pressure, the faster the desorption of the gas attracts the matrix shrinkage effect and causes the coal seam permeability rate to keep increasing. (3) The improvement of gas drainage with the overlapping arrangement of two boreholes firstly increases and then decreases as time goes on. (4) When the field test results and numerical simulation of the effective area of gas extraction are compared, the effectiveness of the model is verified. Taking the change of the porosity and the permeability into the model, it is able to calculate the radius of gas drainage more accurately.
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Gao, Kui, Guodong Qiao, Zegong Liu, and Wei Xia. "Damage Characteristics Caused by Deep-Hole Blasting near Normal Fault and Its Effects on Coal and Gas Outbursts." Geofluids 2022 (April 13, 2022): 1–13. http://dx.doi.org/10.1155/2022/2421492.
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To understand the stability of coal and rock in areas of normal faults disturbed by the dynamic loads of blasting, the damage characteristics of coal and rock within a normal fault are investigated using similarity simulation tests. The mechanism for coal and gas outbursts within a normal fault is analyzed theoretically, and the results indicate that the maximum tensile stress in the vertical direction of the blasting hole in the normal-fault model is 1.17 times that in the no-fault model. The propagation of cracks near the blasting hole produces crushing circles, and more cracks are produced in the normal-fault model, causing severe damage to the coal seam and floor rock adjacent to the upper wall of the normal fault. Meanwhile, coal on the surface of the coal seam falls off. The cracks extend to the roof rock through the footwall of the normal fault. Cracks in the adjacent strata and coal seam interpenetrate those around the blasting hole, which is a potentially dangerous area for coal and gas outbursts. The cumulative damage caused by blasting vibrations increases the extent and scope of the damage to coal and rock, and broken coal and rock provide weak surfaces and gas flow channels that can lead to dynamic gas disasters. The research results will provide a theoretical basis for gas dynamic disasters induced by blasting disturbance in normal fault structures. Based on cases of coal and gas outbursts in the Didaoshenghe Coal Mine in Heilongjiang Province, China, an important reason for such incidents is considered to be the blasting areas of normal faults being disturbed by air-powered coal drilling.
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Dunlop, Erik C., David S. Warner, Prue E. R. Warner, and Louis R. Coleshill. "Ultra-deep Permian coal gas reservoirs of the Cooper Basin: insights from new studies." APPEA Journal 57, no. 1 (2017): 218. http://dx.doi.org/10.1071/aj16015.
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There is a vast, untapped gas resource in deep coal seams of the Cooper Basin, where extensive legacy gas infrastructure facilitates efficient access to markets. Proof-of-concept for the 5 million acre (20 000km2) Cooper Basin Deep Coal Gas (CBDCG) Play was demonstrated by Santos Limited in 2007 during the rise of shale gas. Commercial viability on a full-cycle, standalone basis is yet to be proven. If commercial reservoirs in nanoDarcy matrix permeability shale can be manufactured by engineers, why not in deep, dry, low-vitrinite, poorly cleated coal seams having comparable matrix permeability but higher gas content? Apart from gas being stored in a source rock reservoir format, there is little similarity to other unconventional plays. Without an analogue, development of an optimal reservoir stimulation technology must be undertaken from first principles, using deep coal-specific geotechnical and engineering assumptions. Results to date suggest that stimulation techniques for other unconventional reservoirs are unlikely to be transferable. A paradigm shift in extraction technology may be required, comparable to that devised for shale reservoirs. Recent collaborative studies between the South Australian Department of State Development, Geological Survey of Queensland and Geoscience Australia provide new insight into the hydrocarbon generative capacity of Cooper Basin coal seams. Sophisticated regional modelling relies upon a limited coal-specific raw dataset involving ~90 (5%) of the total 1900 wells penetrating Permian coal. Complex environmental overprints affecting resource concentration and gas flow capacity are not considered. Detailed resource estimation and the detection of anomalies such as sweet spots requires the incorporation of direct measurement. To increase granularity, the authors are conducting an independent, basin-wide review of underutilised open file data, not yet used for unconventional reservoir purposes. Reservoir parameters are quantified for seams thicker than 10feet (3m), primarily using mudlogs and electric logs. To date, ~3750 reservoir intersections are characterised in ~1000 wells. Some parameters relate to resource, others to extraction. A gas storage proxy is generated, not compromised by desorption lost gas corrections. A 2016 United States Geological Survey resource assessment, based on Geoscience Australia studies, suggests that the Play remains a world-class opportunity, despite being technology-stranded for the past 10years. Progress has been made in achieving small but incrementally economic flow rates from add-on hydraulic fracture stimulation treatments inside conventional gas fields. Nevertheless, a geology/technology impasse precludes full-cycle, standalone commercial production. A review of open file data and cross-industry literature suggests that the root cause is the inability of current techniques to generate the massive fracture network surface area essential for high gas flow. Coal ductility and high initial reservoir confining stress are interpreted to be responsible. Ultra-deep coal reservoirs, like shale reservoirs, must be artificially created by a large-scale stimulation event. Although coal seams fail the reservoir ‘brittleness test’ for shale reservoir stimulation practices, the authors conclude from recent studies that pervasive, mostly cemented or closed coal fabric planes of weakness may instead be reactivated on a large scale, to create a shale reservoir-like stimulated reservoir volume (SRV), by mechanisms which harness the reservoir stress reduction capacity of desorption-induced coal matrix shrinkage.
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Bell, R. M. "METHANE DRAINAGE POTENTIAL OF THE NORTHERN BOWEN BASIN." APPEA Journal 27, no. 1 (1987): 281. http://dx.doi.org/10.1071/aj86022.
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Large volumes of methane plus some other gases are generated during the coalification process. Under suitable conditions some of this gas is adsorbed within the microporosity of coals. The rate at which the gas can desorb is a function of the permeability, degree of fracturing or cleating, moisture content, geochemistry of the coals, and the pressure differential. Flow rates from coals are generally low but can be dramatically improved by artificial stimulation and techniques such as lateral drilling.Methane drainage or coal de-methanisation has been carried out for many years, primarily for safety reasons. The resource value of methane in coal seams is now being recognised and considerable research is being undertaken both overseas and in Australia.In the Northern Bowen Basin, several million tonnes of coal are mined each year. The main seams of the Permian Collinsville, Moranbah, German Creek, and Rangal Coal Measures are generally thick and laterally extensive. The area north of Blackwater probably contains more than 100 billion tonnes of coal from which several hundred billion m3 (several Bcf) methane could conceivably be recovered in those areas where the coals are too deep for commercial exploitation.The coals of the Northern Bowen Basin are considered to have better physical parameters for the commercial development of methane drainage projects than those of the central and southern Bowen Basin where methane drainage projects were undertaken several years ago. It is estimated that more than 85 million m3 (3 Bcf) of recoverable gas per square km could be present in some areas. This gas can probably be produced for less than $1.50/GJ (1 Mcft, a figure which compares favourably with many conventional natural gas sources.The Northern Bowen Basin is well-situated with respect to potential gas markets at Townsville and Gladstone. The gas could also be used as a chemical feedstock for products such as ammonia, fertilisers, explosives or synfuels, with the plants located close to the producing wells, thus significantly reducing gas transport costs.
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Liu, Jian, and Qian Le. "Experimental Study on Deep Borehole Pre-Cracking Blasting of Drilling through Strata at Low Permeability Seam." Advanced Materials Research 868 (December 2013): 339–42. http://dx.doi.org/10.4028/www.scientific.net/amr.868.339.
Full textAbstract:
In the process of roadway excavation in the low permeability outburst coal seam, with drilling through strata in the bottom drainage roadway extracting coal seam gas of control area. In order to improve extraction effect, the method that deep borehole pre-cracking blasting is used to increase the permeability of coal in the drilling through strata seam segment is proposed. The calculation formula on crushing circle and crack circle radius of deep borehole pre-cracking blasting are derived, and the effective loosening radius of blasting is calculated in theory, the research achievements are applied to field test, the test results show that deep borehole pre-cracking blasting permeability improvement technology is carried out in the drilling through strata of the low permeability outburst coal seam, the permeability of coal seam is improved by 180 times, the gas extraction scalar is raised by 8-10 tomes, during the process of roadway excavation, gas concentration of the working face is 0.2%-0.3%, and tunneling footage is increased by 2 times.
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Qi, Qingjie, Xinlei Jia, Xinhua Zhou, and Youxin Zhao. "Instability-negative pressure loss model of gas drainage borehole and prevention technique: A case study." PLOS ONE 15, no. 11 (November 23, 2020): e0242719. http://dx.doi.org/10.1371/journal.pone.0242719.
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The internal collapse of deep seam drainage borehole and negative pressure loss represents a serious technical problem affecting gas drainage. To address this problem a creep model of coal around borehole was established based on the plastic softening characteristics of coal. The final collapse time of the borehole was determined and used to derive the three stages of the borehole collapse process. The model of negative pressure loss in drainage borehole was established according to the theory of fluid dynamics, the model of methane gas flow and the creep model of the coal around the borehole. The relationship between the negative pressure loss of drainage and the change of borehole aperture was derived, thereby revealing the main influencing factors of the negative pressure loss in the borehole. A drainage technique named “Full-hole deep screen mesh pipe” was introduced and tested to prevent the collapse of borehole and reduce the negative pressure loss. The result shows that after the borehole was drilled, the borehole wall was affected by the complex stress of the deep coal seam, the coal surrounding the borehole collapsed or presented the characteristics of creep extrusion towards the borehole. The “Full-hole deep screen mesh pipe drainage technology” could effectively control the collapse as well as the deformation of the borehole and reduced the negative pressure loss. Compared with the traditional drainage technology, the methane gas drainage concentration was increased by 101% and the gas flow was increased by 97% when the methane gas was drained for 90 days, the gas drainage efficiency increased significantly.
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Teng, Teng, Yuming Wang, Xiaoyan Zhu, Xiangyang Zhang, Sihai Yi, Guowei Fan, and Bin Liu. "Numerical Analysis on the Storage of Nuclear Waste in Gas-Saturated Deep Coal Seam." Geofluids 2021 (July 11, 2021): 1–12. http://dx.doi.org/10.1155/2021/3277131.
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Nuclear power has contributed humanity a lot since its successful usage in electricity power generation. According to the global statistics, nuclear power accounts for 16% of the total electricity generation in 2020. However, the rapid development of nuclear power also brings up some problems, in which the storage of nuclear waste is the thorny one. This work carries out a series of modeling and simulation analysis on the geological storage of nuclear waste in a gas-saturated deep coal seam. As the first step, a coupled heat-solid-gas model with three constitutional fields of heat transfer, coal deformation, and gas seepage that based on three governing conservation equations is proposed. The approved mechanical model covers series of interactive influences among temperature change, dual permeability of coal, thermal stress, and gas sorption. As the second step, a finite element numerical model and numerical simulation are developed to analyze the storage of nuclear waste in a gas-saturated deep coal seam based on the partial differential equations (PDE) solver of COMSOL Multiphysics with MATLAB. The numerical simulation is implemented and solved then to draw the following conclusions as the nuclear waste chamber heats up the surrounding coal seam firstly in the initial storage stage of 400 years and then be heated by the far-field reservoir. The initial velocity of gas flow decreases gradually with the increment of distance from the storage chamber. Coal gas flows outward from the central storage chamber to the outer area in the first 100 years when the gas pressure in the region nearby the central storage chamber is higher than that in the far region and flows back then while the temperature in the outer region is higher. The modeling and simulation studies are expected to provide a deep understanding on the geological storage of nuclear waste.
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Tang, Songlei, Hongbo Zhai, Hong Tang, and Feng Yang. "Isothermal Desorption Hysteretic Model for Deep Coalbed Methane Development." Geofluids 2022 (January 25, 2022): 1–9. http://dx.doi.org/10.1155/2022/5259115.
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The adsorption/desorption mechanism of coalbed methane is significant for gas control and coalbed methane exploitation; scholars have done a lot of research on it and generally have confidence in that temperature, pressure, and moisture are central factors affecting the adsorption of coalbed methane. Considering the reduction of recovery efficiency caused by desorption hysteresis in deep coalbed methane drainage, the effects of high reservoir pressure, high gas content, and low permeability on the hysteresis index were analyzed. A desorption hysteresis model based on the combination of dual-porosity media and traditional Langmuir adsorption theory was proposed. By comparing with the four experimental data of Ma et al., the advantages of the new model in fitting desorption data were investigated. Based on the new desorption hysteresis model, the hysteresis index was calculated from the adsorption capacity and desorption capacity under the abandonment pressure. The hysteresis index under different coal sizes and adsorption pressure were calculated, and a good linear relationship was found between the adsorption pressure and the hysteresis index. Through a large number of field production data analysis, the following conclusions are drawn: as the adsorption pressure increases, the hysteresis index enhances; when the coal sample size increases, the hysteresis index also increases. Finally, by comparing experimental data from deep and shallow coal samples, the influence of desorption hysteresis on deep coalbed methane mining was explored. This paper draws the conclusion that although the gas content in deep coalbed methane is considerable, its hysteresis index is also enhanced, which makes coalbed methane development more difficult. The findings of this study can provide theoretical support for coal bed gas control and coal bed methane heat injection mining.
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Wang, Xiangyu, Hongwei Zhou, Lei Zhang, Wei Hou, and Jianchao Cheng. "Dual-Zone Gas Flow Characteristics for Gas Drainage Considering Anomalous Diffusion." Energies 15, no. 18 (September 15, 2022): 6757. http://dx.doi.org/10.3390/en15186757.
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Gas drainage in deep coal seam is a critical issue ensuring the safety of mining and an important measure to obtain gas as a kind of clean available energy. In order to get a better understanding of gas flow and diffusion for gas drainage in deep coal seams, a dual-zone gas flow model, including the drainage damage zone (DDZ) and the non-damaged zone (NDZ), are characterized by different permeability models and anomalous diffusion models to analyze the influence of damage induced by drilling boreholes on gas flow. The permeability model and anomalous diffusion model are verified with experiment and field data. A series of finite-element numerical simulations based on developed models are carried out, indicating that, compared with normal diffusion model, the anomalous diffusion is more accurate and appropriate to field test data. The coal fracture permeability increases rapidly with the distance decreasing from the borehole, and the area of DDZ is increasing significantly with the extraction time. Moreover, with the increasing of fractional derivative order, the diffusion model transforms the anomalous diffusion to the normal gradually, and the decay of gas pressure is aggravated. The higher value of non-uniform coefficient results in the larger increment of fracture permeability. The permeability–damage coefficient increase makes the increment of fracture permeability bigger.
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Cai, Feng, and Ze Gong Liu. "Research on Similar Materials Simulation Test for Protective Coal-Seams of Group B Coal-Seams of Panyi Coal Mine of China." Applied Mechanics and Materials 204-208 (October 2012): 1389–94. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.1389.
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Protective technology is one of most effective technologies for regional gas control technology. Huainan Coal Field is a typical coal field with deep and low permeability multi coal-seams, and it is one of most serious coal field in gas disasters. Currently, Huainan Coal Field has completely entered the stage of extracting Group B coal-seams (average mining depth is about 650m). In order to research and obtain the results of stress relief of adjacent coal-seams after extracted protective coal-seam, taking advantage of the method of similar materials simulation test and taking 11415 longwall panel of Group B coal-seams of Panyi Coal Mine of Huainan Coal Field, the changing trends of abutment pressure, displacement as well as permeability of adjacent coal-seams are systematically studied. The researching results can provide safeguard for high-effective gas drainage, eliminate the risk of coal and gas outburst as well as high effective production.
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Yuan, Anying, Guangsheng Fu, and Junling Hou. "A Multiscale Structural Analysis of Soft and Hard Coal Deposits in Deep High-Gas Coal Seams." Advances in Civil Engineering 2021 (March 18, 2021): 1–11. http://dx.doi.org/10.1155/2021/8865038.
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In recent years, with the increases in coal mining depths, the risk of coal seam outburst occurrences has increased. Therefore, it is of major significance to study the multiscale structures of soft and hard coal deposits in order to prevent and control the coal and gas outbursts. In this research investigation, soft and hard coal multiscale structures were comprehensively examined using various laboratory methods. The results revealed the following: (1) From a macrostructural aspect, the physical and mechanical properties of the soft coal were weaker than those of the hard coal. It was found that the majority of the examined specimens were characterized by scaly structures without blocks larger than 50 mm. The hard coal was observed to be mainly massive with only a small part being clastic. Therefore, the structural characteristics were considered to be stable. (2) From a microstructural perspective, the surfaces of the soft coal specimens were observed to be rough. The pores were found to be more developed, with the edge of pores being mainly hackly. At the same time, fractures were also relatively developed, showing good connectivity. (3) From a micropore structural perspective, it was found that the BET-specific surface areas and BJH-specific surface areas of the soft coal specimens were higher than those of the hard coal specimens, which indicated that the gas adsorption and diffusion migration abilities of the soft coal were greater than those of the hard coal. (4) It was suggested from the study results that the ventilation and gas extraction processes should be strengthened in the mining activities of coal seams with high, soft stratification content. At the same time, the methods used for water injection modification should be enhanced in order to improve the mechanical stability of soft coal. Consequently, the instantaneous released gases will be decelerated, and the occurrences of coal and gas outburst events in mine working faces can be prevented.
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Salmachi, Alireza, Erik Dunlop, and Mojtaba Rajabi. "Drilling data of deep coal seams of the Cooper Basin: analysis and lessons learned." APPEA Journal 58, no. 1 (2018): 381. http://dx.doi.org/10.1071/aj17055.
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Deep (>4920 ft; >1500 m) coal seams of the Cooper Basin accommodate large amounts of natural gas; however, permeability of this unconventional resource is low and reservoir stimulation in prospective coal intervals is essential to achieve commercial production. This paper aims to analyse drilling data of deep coal seams of the Cooper Basin in South Australia. Drilling data obtained from mud logs are utilised to construct a drillability index (DI), in which rate of penetration is normalised by drilling factors, making DI more sensitive to coal rock strength. Analysis of DI and gas show information provides a preliminary screening tool for studying prospective deep coal seams, before performing in-depth reservoir characterisation and production tests. The decline in DI with depth is attributed to a compaction effect that makes deeper coal seams more difficult to drill through compared with shallow seams. The existence of a fracture network can reduce coal rock strength and consequently DI may increase. The increase in DI may be indirectly related to fluid flow characteristics of the coal seam helping in identifying prospective coal intervals. The DI is also affected by other factors and, hence, should be used in combination with reservoir information to yield conclusive indications. Gas show information and DI results were utilised to indicate the effectiveness of dewatering operation and hydraulic fracture confinement in the wells drilled in the Klebb area located in the Weena Trough.
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OHGA, KOTARO, SOHEI SHIMADA, and EIJI ISHII. "GAS EMISSION PREDICTION AND CONTROL IN DEEP COAL MINES." Mineral Resources Engineering 09, no. 02 (June 2000): 239–54. http://dx.doi.org/10.1142/s0950609800000196.
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Gu, Beifang, and Yanling Wu. "Research and Application of Hydraulic Punching Pressure Relief Antireflection Mechanism in Deep “Three-Soft” Outburst Coal Seam." Shock and Vibration 2021 (July 1, 2021): 1–10. http://dx.doi.org/10.1155/2021/7241538.
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To solve the problems of gas predrainage in deep seams with “three softs” and low-air permeability, hydraulic punching pressure relief antireflection technology is proposed on the basis of the research background of gas predrainage technology in Lugou Mine to alleviate technical problems, such as low gas drainage efficiency, in this mine. Through the analysis of the mechanism of hydraulic punching and coal breaking, combined with FLAC3D software, a hydraulic punching pressure relief antireflection model is established. Then, the fracture radii of coal rock are simulated and calculated. The results show that, under hydraulic punching with a water pressure of 10 MPa and coal outputs of 3 m3, 6 m3, 9 m3, and 12 m3, the fracture radii of coal and rock are 3.4 m, 4.8 m, 5.5 m, and 5.9 m, respectively. Using the software to fit the relationship between coal output V and hydraulic punching fracture radius R under the same water pressure, R = 2.32479 V0.3839 is obtained. The field test is carried out in the bottom drainage roadway of 32141 in Lugou Mine. The application effect is as follows: the gas concentration of hydraulic punching with a coal output of 3 m3 is twice that of ordinary drilling, and the coal output of hydraulic punching with a coal output of 6 m3 is four times that of ordinary drilling. The extraction concentration is four times that of ordinary drilling, and the extraction concentration of hydraulic punching with a coal output of 9 m3 is 6.4 times that of ordinary drilling. Combining the results of the numerical simulation and taking into account the actual construction situation on site, the coal output of water jetting from the borehole is 9 m3, and the fracture radius is 5.5 m. This outcome means that the effective half radius is 5.5 m, and the borehole spacing is 7.7 m. These values are the construction parameters for large-scale applications. This proposal provides effective technology and equipment for gas drainage in the deep three-soft coal seam. Consequently, it has promotion and reference significance for gas drainage in coal seam of the same geological type.
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Zhang, Xue-Bo, Shuai-Shuai Shen, Xiao-Jun Feng, Yang Ming, and Jia-jia Liu. "Influence of Deformation and Instability of Borehole on Gas Extraction in Deep Mining Soft Coal Seam." Advances in Civil Engineering 2021 (March 6, 2021): 1–11. http://dx.doi.org/10.1155/2021/6689277.
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To study the effects of the three deformation instability modes of gas drainage borehole on gas drainage, the deformation instability mechanism of soft coal seams is analyzed, three deformation instability modes are proposed for soft coal seams, namely, complete holes, collapse holes, and plug holes, and a solid-fluid coupling model incorporating dynamic change of borehole suction pressure is established. The results of the study show the following. (1) When there is no borehole deformation (i.e., complete borehole), the suction pressure loss of drainage system in the borehole is very small, whose effect on gas drainage can be neglected. (2) In case of borehole collapse, the suction pressure loss is big at the collapse segment, and the total suction pressure loss of the drainage system in the borehole is bigger than that in the complete hole. However, it is smaller than the suction pressure of the drainage system and exerts limited effect on gas drainage. As the borehole collapse deteriorates, the effective drainage section of the borehole becomes smaller, while the suction pressure loss in the borehole increases continuously; thus, the gas drainage effect continuously worsens. (3) In case of plug hole, a continuous medium forms between the plug segment coal body and the surrounding coal seam, the plug segment drainage pressure turns into coal-bed gas pressure, and effective drainage length of the borehole shortens, seriously affecting the gas drainage effect. The study carries important theoretical guiding significance for improving gas drainage effect and effectively preventing gas disasters.
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Khlystov, O. M., A. V. Vainer-Krotov, A. V. Kitaev, and T. V. Pogodaeva. "Occurrence of Tankhoy field coals in South Baikal bottom sediments." Earth sciences and subsoil use 44, no. 3 (October 30, 2021): 285–92. http://dx.doi.org/10.21285/2686-9993-2021-44-3-285-292.
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The purpose of the study is to describe the first finds of coal-bearing clays and coals in the bottom sediments of the southern basin of Lake Baikal and compare them with terrestrial coal-bearing deposits of the Tankhoy field. Comparative analysis of the lithological composition and colour of bottom sediments and terrestrial sections, as well as the concentration of organic carbon and conducted palynological analysis allowed their correlation. At the lake’s depth of 900 m the authors discovered a coal-bearing strata in situ (st 56), which later was stratigraphically correlated with the terrestrial coalbearing part of the Tankhoy suite. The fragments of coal found in bottom sediments basically along the entire Tankhoy field, especially bedrock coals on the underwater slope in South Baikal up to 1300 m deep prove the distribution of the coal-bearing part of the Tankhoy suite in the sublacustrine part of the lake throughout the entire slope (from 5 to 10 km offshore) and confirm the distribution area of the Tankhoy paleolake over a significant area of the contour of modern southern basin of Lake Baikal. The finds of coal-bearing strata on these and other various sub-bottom depths, i.e. under various pressure and temperature conditions, suggest that coals themselves and coal-bearing mudstones may be a generation facility of secondary microbial methane. This should be taken into account when searching for gas hydrocarbon and gas hydrate accumulations as well as assessing methane cycles in Lake Baikal.
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Dong, Guowei, Xuanming Liang, and Qixiang Wang. "A New Method for Predicting Coal and Gas Outbursts." Shock and Vibration 2020 (June 24, 2020): 1–10. http://dx.doi.org/10.1155/2020/8867476.
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In view of the fact that coal and gas outbursts are difficult to predict, a new method for predicting coal and gas outbursts was proposed based on occurrence mechanisms of coal and gas outbursts relating to coal mass strength, gas pressure, and in situ stress. The method revealed that the rate of occurrence of coal and gas outbursts in mines was 5% to 10% and gas pressures for coal and gas outbursts in shallow and deep mines in China were greater than 0.74 and 0.6 MPa, respectively. The prediction index for coal and gas outbursts based on the gas factor was the gas desorption index of drilling cuttings (K1), which is referred to the gas content desorbed from the coal mass in the first minute of drilling. The prediction index for coal and gas outbursts based on coal mass strength was the thickness of a soft layer that could be twisted into powder by hand. Based on many cases of coal and gas outbursts, the critical thickness of the soft layer was found to have been 0.2 m. The prediction index for coal and gas outbursts based on in situ stress was the weight of drilling cuttings, which represented the mass of drilling cuttings per linear metre of boreholes with diameters of 42 or 75 mm. Finally, the new prediction method and prediction index critical values for coal and gas outbursts were verified based on industrial application tests. This method has been widely applied on-site and obtained good prediction results.
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Wu, Haojun, Min Gong, Xiaodong Wu, and Yang Guo. "Effect and Response of Coal and Rock Media Conditions on Deep-Hole Pre-Splitting Blasting Techniques for Gas Drainage." Energies 15, no. 22 (November 20, 2022): 8733. http://dx.doi.org/10.3390/en15228733.
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Different types of deep-hole blasting techniques are needed to solve gas drainage problems in complex and variable cases. Blasting parameters suitable for mines are selected based on the relationship between blast stress field changes and gas flow combined with field application and numerical simulation. The Datong Mine was a background to study the blast crush zone and drainage influence range following deep-hole blasting with holes laid in coal seams, which resulted in a 24% increase in gas flow in the drainage hole 6 m from the blast hole. In response to the difficulty of forming blast holes in the soft coal seam of the Yuyang Mine, drilling and blasting in the floor rock stratum adjacent to the coal seam increased the gas flow in the drainage holes by 125%. When applying the deep-hole technique with holes crossing multi-seams for gas drainage in Shiping Mine, the volume of gas drainage increases significantly with increased effective stress in the drainage hole. For example, when the spacing at the hole’s bottom between the blast hole and the drainage hole is 4.6 m, the volume of gas drainage increases by 3.3 times, compared with 8.8 m. Twenty-six protruding mines in southern China have applied the above deep-hole pre-splitting blasting technology, all of which have achieved good results and are of great significance to future applications in multiple fields, such as gas control.
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Gao, Xiang-Dong, Yan-Bin Wang, Xiang Wu, Yong Li, Xiao-Ming Ni, and Shi-Hu Zhao. "Nanoscale Pore Structure Characteristics of Deep Coalbed Methane Reservoirs and Its Influence on CH4 Adsorption in the Linxing Area, Eastern Ordos Basin, China." Journal of Nanoscience and Nanotechnology 21, no. 1 (January 1, 2021): 43–56. http://dx.doi.org/10.1166/jnn.2021.18444.
Full textAbstract:
The high gas content of deep coal seams is a driving force for the exploration and development of deep coalbed methane (CBM). The nanoscale pores, which are the main spaces for adsorption and storage of CBM, are closely related to the burial depth. Based on integrated approaches of vitrinite reflectance (Ro), maceral composition, scanning electron microscope (SEM), proximate analysis, fluid inclusion test, low-temperature N2 adsorption–desorption, and CH4 isothermal adsorption, the nanoscale pore structure of coals recovered at depths from 650 to 2078 m was determined, and its influence on the CH4 adsorption capacity was discussed. The results show that the coal rank has a good linear relationship with the current burial depth of the coal seams; that is, the influences of the burial depth on the coals can be reflected by the influences of the coal rank on the coals. With the increase in the coal rank, the moisture and volatile content decrease, and the fixed carbon content increases. The variation in the pore volume and specific surface area with the increase in the coal rank can be divided into two stages: the rapid decline stage (when 0.75%<Ro < 1.0%), dominated by the compaction and gelatinization, and the slow decline stage (when 1.0%<Ro < 1.35%), characterized by the low stress sensitivity and the mass production of secondary pores. The percentage of micropores increases throughout the process. When 10 nm is taken as the boundary, the nanoscale pores show different fractal features. When Ro < 1.0%, the fractal dimension (FD) of the micropores is close to 3. When Ro > 1.0%, the FD of the micropores is close to 2. This indicates that with the increase in the degree of coalification, the surface of the micropores is simpler. The above results show that the gas adsorption capacity of coal first slightly decreases (when 0.75% < Ro < 1.0%) and then increases (when 1.0% < Ro < 1.35%), and the coincident results are shown in the Langmuir volume (VL) test results.
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Cao, Jianjun, Benqing Yuan, Siqian Li, Zunyu Xu, Qihan Ren, and Zhonghua Wang. "Research on Pressure Relief Method of Close Floor Roadway in Coal Seam Based on Deformation and Failure Characteristics of Surrounding Rock in Deep Roadway." Geofluids 2022 (March 30, 2022): 1–16. http://dx.doi.org/10.1155/2022/5820228.
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To solve the high-stress hazard faced in the process of deep mining process, the pressure relief characteristics of gas bearing coal and the deformation characteristics of surrounding rock in deep roadway are studied by means of laboratory test, similar simulation analysis, and field investigation. The investigation results and engineering application showed that the specimens could more easily reach the failure point due to the axial pressure relief under high confining pressure. In addition, the deformation and failure degree of the surrounding rock was higher due to the disturbance from the deep high-stress roadway. The scope of the height affected by the pressure relief of the overlying strata reached above 10 m. Moreover, the initial gas emission could reach 4.41–14.39 times that of the original coal seam by drilling a hole in the coal seam at 10 m from the roof. Thus, the short-distance floor roadway exerted an obvious pressure relief effect on the overlying coal seam.
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Wu, Xiang, Zhen Yang, and Dongdong Wu. "Advanced Computational Methods for Mitigating Shock and Vibration Hazards in Deep Mines Gas Outburst Prediction Using SVM Optimized by Grey Relational Analysis and APSO Algorithm." Shock and Vibration 2021 (April 24, 2021): 1–11. http://dx.doi.org/10.1155/2021/5551320.
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Gas outburst poses a huge threat to the safe production of coal mines. Therefore, the prediction of gas outburst has always been a hot topic for researchers. In recent years, the use of artificial intelligence algorithms for gas outburst prediction has made progress, such as using BP neural network, GA algorithm, and SVM algorithm. Despite these progresses, predicting the gas outburst more accurately and efficiently still remains a great challenge. In this work, an algorithm based on grey relational analysis and SVM using adaptive particle swarm optimization (APSO-SVM) for gas outburst prediction is proposed. Grey relational analysis was used to extract the four most relevant ones from nine gas outburst prediction parameters (geological structure zone distance, coal seam gas content, gas release initial velocity, gas desorption index-K1, drill cuttings volume, coal seam depth, coal seam thickness, coal destruction type, and coal firmness coefficient) to give the needed parameters for SVM model. Higher prediction accuracy was then obtained with the selected parameters composed by coal seam gas content, gas release initial velocity, gas desorption index-K1, and drill cuttings volume. Moreover, adaptive particle swarm optimization (APSO) was used to optimize the penalty factor and kernel parameters of the support vector machine to improve the global search ability and avoid the occurrence of the local optimal solutions. The APSO-SVM model was applied to the prediction of gas outburst in 31004 tunneling face of Xinyuan Coal Mine, Yangquan City, Shanxi Province, China. We further introduced the criteria of accuracy, precision, recall, and F 2 -score to evaluate the prediction results of different models. The results show that, in the gas outburst prediction, the accuracy of the APSO-SVM model is 98.38%, the precision and recall are both 100%, and F 2 -score is 1. Comparative studies confirm that APSO-SVM displayed better performance than SVM and PSO-SVM models for the applied grey relational analysis assisted gas outburst prediction. These obtained results indicate the validity of APSO-SVM model for gas outburst prediction.
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Wang, Lin, Xi Xi Li, and Yu Xiang Zhao. "The Practice about Deep Hole Pre-Split Blasting in Mining Faces of Low Permeability Extra-Thick Seam." Advanced Materials Research 524-527 (May 2012): 781–85. http://dx.doi.org/10.4028/www.scientific.net/amr.524-527.781.
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The rate of gas drainage is lower in mining faces of low permeability of extra-thick seam, and with lots of gas emission, which brings greater security risks. Through the Pre-pumping experiment of deep hole pre-split blasting for 216 mechanized mining face in Xiashijie coal mine of TongChuan coal group, increased the rate of gas drainage over 17% in working surface, that reduced potential safety problems during production, and indicated the direction for later gas government.
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Jiang, Junjun, Yong Zhang, Zhigang Deng, Weiguang Ren, and Guanghui Zhang. "Experimental Study on Mechanical Behavior and Energy Evolution Characteristics of Gas-Filled Deep Coal under Cyclic Loading." Processes 11, no. 2 (January 18, 2023): 316. http://dx.doi.org/10.3390/pr11020316.
Full textAbstract:
To study the mechanical behavior and energy evolution law of gas-filled deep coal, conventional triaxial compression experiments under different confining pressure and gas pressure conditions and cyclic loading and unloading experiments under different gas pressures were carried out. The failure characteristics and mechanical parameters evolution of two loading modes were analyzed. In addition, the energy density and ratio evolution law under cyclic loading was revealed, and based on these findings, an attempt was made to depict the relation of cumulative dissipated energy density and volumetric strain by fitting the experimental data. The results indicated that failure of coal is expressed as a single shear surface under conventional compression, while under cyclic loading mode, coal behaves with multi-fracture crushing failure. Mechanical parameters showed a trend of decay with increasing gas pressure, and that cyclic loading and unloading increases the bearing capacity of coal by 8–38%. The dissipated energy density and ratio grew significantly when coal entered the yield stage. In the compaction stage, the cumulative dissipated energy density rose with volumetric strain in the form of an exponential function, and it increased with relative volumetric strain as a power function.
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Zhang, Dengfeng, Shuaiqiu Jia, Haohao Wang, Peili Huo, Jin Zhang, and Jun Tao. "Interactions of Sulfur Dioxide with Coals: Implications for Oxy-coal Combustion Flue Gas Sequestration in Deep Coal Seams." Energy & Fuels 31, no. 5 (April 27, 2017): 5333–43. http://dx.doi.org/10.1021/acs.energyfuels.7b00136.
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Gordienko, M. O. "The selection of technological basis of deep processing of coal." Journal of Coal Chemistry 4 (2021): 15–21. http://dx.doi.org/10.31081/1681-309x-2021-0-4-15-21.
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THE SELECTION OF TECHNOLOGICAL BASIS OF DEEP PROCESSING OF COAL © M.O. Gordienko (State Enterprise "Ukrainian State Research Coal Chemical Institute (UHIN)", 61023, Kharkov, Vesnina st., 7, Ukraine) The article is devoted to the analysis of the possibility of expanding the raw material base of thermal energy, as well as meeting the demand for motor fuels and chemical products through the thermochemical processing of coal, the reserves of which are large enough and available for extraction and transportation. Moreover, in contrast to technologies such as methanization and liquefaction, the most promising type of deep processing of coal seems to be its gasification. This process is carried out in sealed devices of high power according to the technologies that have a long history of improvement on an industrial scale by the world's leading companies. It was emphasized that Ukraine has significant reserves of low-calorie coal (constantly expanding due to waste of coal preparation), the thermochemical processing of which can significantly expand the domestic energy base. The basic principles of classification and technological foundations of existing industrial and industrial research installations for gasification of coal and similar materials are given. The basic diagrams and main parameters of the existing installations, which carry out the gasification process at temperatures below the melting point of the mineral (ash-forming) components of the raw material, are described - Sasol Lurgi and SES Gasification Technology (SGT). Based on the data on the world experience in the operation of thermochemical coal processing units, it is shown that low-temperature (carried out at a temperature below the melting point of the mineral ashforming components) gasification of various types of non-coking coal with certain technological solutions can be no less effective than more complex and expensive high-temperature technologies. There are grounds for believing that the efficiency of gasification with ash removal in a solid state can be further increased by using some of the technological capabilities available in coke production. Keywords: brown coal, non-coking coals, thermochemical processing, gasification, efficiency, degree of carbon conversion, energy carriers, synthesis gas, environmental safety. Corresponding author M.O. Gordienko, е-mail: yo@ukhin.org.ua
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Gordienko, M. O. "The selection of technological basis of deep processing of coal." Journal of Coal Chemistry 4 (2021): 15–21. http://dx.doi.org/10.31081/1681-309x-2021-0-4-15-21.
Full textAbstract:
THE SELECTION OF TECHNOLOGICAL BASIS OF DEEP PROCESSING OF COAL © M.O. Gordienko (State Enterprise "Ukrainian State Research Coal Chemical Institute (UHIN)", 61023, Kharkov, Vesnina st., 7, Ukraine) The article is devoted to the analysis of the possibility of expanding the raw material base of thermal energy, as well as meeting the demand for motor fuels and chemical products through the thermochemical processing of coal, the reserves of which are large enough and available for extraction and transportation. Moreover, in contrast to technologies such as methanization and liquefaction, the most promising type of deep processing of coal seems to be its gasification. This process is carried out in sealed devices of high power according to the technologies that have a long history of improvement on an industrial scale by the world's leading companies. It was emphasized that Ukraine has significant reserves of low-calorie coal (constantly expanding due to waste of coal preparation), the thermochemical processing of which can significantly expand the domestic energy base. The basic principles of classification and technological foundations of existing industrial and industrial research installations for gasification of coal and similar materials are given. The basic diagrams and main parameters of the existing installations, which carry out the gasification process at temperatures below the melting point of the mineral (ash-forming) components of the raw material, are described - Sasol Lurgi and SES Gasification Technology (SGT). Based on the data on the world experience in the operation of thermochemical coal processing units, it is shown that low-temperature (carried out at a temperature below the melting point of the mineral ashforming components) gasification of various types of non-coking coal with certain technological solutions can be no less effective than more complex and expensive high-temperature technologies. There are grounds for believing that the efficiency of gasification with ash removal in a solid state can be further increased by using some of the technological capabilities available in coke production. Keywords: brown coal, non-coking coals, thermochemical processing, gasification, efficiency, degree of carbon conversion, energy carriers, synthesis gas, environmental safety. Corresponding author M.O. Gordienko, е-mail: yo@ukhin.org.ua
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Yuan, Benqing, Min Tu, Jianjun Cao, and Xiang Cheng. "Pressure Relief and Permeability Enhancement Mechanism of Short-Distance Floor Roadway in Deep Coal Roadway Strip." Geofluids 2022 (March 24, 2022): 1–12. http://dx.doi.org/10.1155/2022/7430025.
Full textAbstract:
A pressure relief and permeability enhancement method through short-distance floor roadway was proposed to solve the difficult outburst prevention during the gas extraction at the coal roadway strips in deep outburst coal seams with high ground stress and low gas permeability. On the basis of an equivalent model of the surrounding rock in a deep roadway, the analytical solutions of deep roadway excavation to the stress and deformation of pressure relief at overlying short-distance coal roadway strips were obtained using the unified strength theory and nonassociated flow rules. Next, the criteria for determining the reasonable position of floor roadway were established, and a mechanical model of short-distance floor roadway for the pressure relief and permeability enhancement zone at the overlying coal seam was constructed. Finally, the scope of the zonal disintegration at the coal roadway strips in the elastic and elastic–plastic zones of the surrounding rock in the roadway, as well as the expression of gas permeability change, was given. The engineering trial calculation and practice showed that the stress and strain of the surrounding rock in the roadway were evidently influenced by the intermediate principal stress coefficient. Moreover, the vertical stress and vertical displacement of overlying coal seam were gradually reduced with the increase in the intermediate principal stress coefficient and vertical distance of the floor roadway. The minimum reasonable distance arranged for the 213 floor roadway in Qujiang Coal Mine was 6.21 m, and the effective pressure relief should be conducted within 10.6 m from the coal seam floor. When the pressure relief was located at 9.0 m from the coal seam floor, the investigation results were basically consistent with the theoretical analysis results, exerting obvious pressure relief and permeability enhancement effects on the overlying short-distance coal roadway strips.