College of Mining, National University of Science and Technology – MISIS, Moscow, Russia:

Yu. V. Vasyuchkov, Professor, Doctor of Engineering Sciences, vas-yury@yandex.ru

Gas-bearing coal mining is associated with sealed-off draining of mixture of methane and air to bypass mine workings. The second half of the 20th century featured creation and introduction of methods to predict methane release in underground excavations, as well as technologies and techniques of coalbed methane drainage, including drilling, vacuum degassing and sealed-off drainage of air and methane mixture to ground surface. Heading with heavy-duty mining machinery required new approaches and means to intensify gas drainage in order to ensure standard safety and high outputs per development and production faces. However, methane releases in roadways yet remain a serious threat to health and life of miners. This article considers discovered forms of connection of methane with coal matrix, which confirms the existence of strong intermolecular association between methane and its organic microstructure. As regards the forms of connection, there can be nonassociated gas obeying the laws of viscous transfer in fractured-and-porous structure of coal, occluded methane, fixed gas concentrated on inner surface of micropores in coal, methane in the form of solid coal-and-gas solution (absorbed gas) and gas-crystal methane included in crystals of the organic structure of coal. The latter three forms make molecular coalbed methane obeying the laws of diffusion under transfer in coal. For each form of gaseousness, the author quantitatively estimates activation energy required for methane molecules to transfer from bound state to free state. The described gas drainage methods enable reaching the wanted efficiency of coal degassing. Parameters of the existing techniques of coal drainage stimulation are presented. The scope of the analysis embraces the extensive domestic experience gained in hydraulic fracturing and physicochemical treatment of gas-bearing coal beds based on high-pressure injection of power fluids to create extensive permeable fracturing patterns for deep coal-mine drainage.

1. About the prospects of coal gas mining in Russia. Gasprom. Available at: http://www.gazprom.ru/about/production/extraction/metan/ (accessed: 12.09.2016). (in Russian)
2. Natural Gas. Coalbed Methane Production. Energy Information Agency. Available at: http://www.eia.gov/dnav/ng/ng_prod_coalbed_s1_a.htm/Natural Gas. Coalbed Methane Production (accessed: 20.09.2016).
3. Alekseev A. D., Ayruni A. T., Vasyuchkov V. F., Zverev I. V., Sinolitskiy V. V., Dolgova M. O., Ettinger I. D. A property of organic coal substance to form the metastable single-phase systems with gases by the types of solid solutions : scientific event. Russian Academy of Natural Sciences. Diploma No. 9. Available at : http://www.raen.info/activities/reg/-o (accessed: 25.09.2016).
4. Seidle J. Fudaments of Coalbed Methane. Reservoirs Engineering. Penn Well Books. 2011. pp. 126, 347.
5. Ettinger I. L., Lidin G. D. Physical chemistry of gas-bearing coal seam. Moscow : Nauka, 1981. 104 p.
6. Vasyuchkov Yu. F. Physical-chemical methods of degassing of coal layers. Moscow : Nedra, 1986. 255 p.
7. Pan Z., Connell L. D. A theoretical model for gas adsorption-induced coal swelling. International Journal of Coal Geology. 2007. Vol. 69, No. 4. pp. 243–252.
8. Chena Z., Pan Z., Liua J., Luke D., Connell B., Elsworth D. Effect of the effective stress coefficient and sorption-induced strain on the evolution of coal permeability: Experimental observations. International Journal of Greenhouse Gas Control. 2011. Vol. 5, Iss. 5. pp. 1284–1293.
9. Zhang H., Liu J., and Elsworth D. How sorption-induced matrix deformation affects gas flow in coal seams: a new FE model. International Journal of Rock Mechanics and Mining Sciences. 2008. Vol. 45, No. 8. pp. 1226–1236.
10. Zakharov V. N., Zaburdyaev V. S., Kuzminich S. V., Chekmenev A. Yu. Coal Mine Degassing System Improvement. Ugol. 2013. No. 4. pp. 56–59.
11. Bykova M. Yu. Decisions towards higher operating efficiency of local coal–gas–power complexes. Gornyy informatsionno-analiticheskiy byulleten. 2013. No. 12. pp. 357–360.
12. Bykova M. Yu. Ecological evaluation procedure for a local coal–gas–electric plant. Gornyy informatsionno-analiticheskiy byulleten. 2013. No. 11. pp. 311–314.
13. Slastunov S. V., Ermak G. P. Choice Substantiation of Efficient Implementation of Degassing Methods in Case of Intensive Gas-bearing Coal Beds a Key Issue for Ensuring Coal Mine Methane Safety. Ugol. 2013. No. 1. pp. 21–24.
14. Pinkun G., Yuanping C. Permeability Prediction in Deep Coal Seam: A Case Study on the No. 3 Coal Seam of the Southern Qinshui Basin in China. The Scientific World Journal. 2013. Vol. 2013. p. 10. doi: dx.doi.org/10.1155/2013/161457
15. Koryaga M. G., Voloshin V. A., Sychev I. I. Coal bed methane as an alternative to shale gas. Gornyy informatsionno-analiticheskiy byulleten. 2015. No. 3. pp. 372–379.
16. Kosterenko V. N., Timchenko A. N., Vorobeva O. V. Analysis of causes of accidents to improve occupational safety control efficiency in mines. Gornyy informatsionno-analiticheskiy byulleten. 2015. No. 12. pp. 194–199.
17. Mokhnachuk I. I., Myshlyaev B. K. On Improvement of Efficiency and Safety in Operation at Mines of the Russian Federation. Ugol. 2014. No. 2. pp. 11–14. No. 19.