Definition, theory, methods, and applications of the safe and efficient simultaneous extraction of coal and gas

Abstract

Simultaneous extraction of the coal and gas is an effective method of eliminating coal mine gas disasters while safely exploiting the coal and achieving efficient gas drainage in China, which is widely accepted by the main coal-producing countries around the world. However, the concrete definition of simultaneous extraction is vague and there is little accurate theoretical support for the simultaneous extraction of coal and gas, which makes it difficult to determine an efficient gas drainage method appropriate to the features of coal seams. Based on theoretical analysis, laboratory tests and field observations, a specific definition of simultaneous extraction of coal and gas is proposed after analyzing the characteristics of coal seam occurrences in China, and we developed the mechanism of mining-enhanced permeability and established the corresponding theoretical model. This comprises a process of fracture network formation, in which the original fractures are opened and new fractures are produced by unloading damage. According to the theoretical model, the engineering approaches and their quantitative parameters of 'unloading by borehole drilling' for single coal seams and 'unloading by protective seam mining' for groups of coal seams are proposed, and the construction principles for coal exploitation and gas-drainage systems for different conditions are given. These methods were applied successfully in the Tunlan Coal Mine in Shanxi Province and the Panyi Coal Mine in Anhui Province and could assure safe and efficient simultaneous extraction of coal and gas in these outburst coal mines.

Influence radius of gas extraction borehole in an anisotropic coal seam: Underground in‐situ measurement and modeling

“…where v f is the gas velocity, m/s; μ is the gas dynamic viscosity, Pa.s; c is the Klinkenberg coefficient, MPa, and ▽p is the pressure gradient, MPa/m. The gas flow in coal follows equation (14) 35 :…”

“…For a typical coal mine, methane in ventilation air may contain 0.1%-15% methane, and drained methane via different gas drainage techniques contains 60%-95% methane depending on the gas generation and storage properties of methane in coal seams. 8,13,14 Therefore, how to design a proper borehole arrangement for panels to degas CMM at a specific drainage duration becomes extremely important for mining management. Since methane emission usually comes from mining panels, adjacent (above and below) coal seams, and gob area (caved zone after mining), a variety of techniques, such as in-seam horizontal and cross borehole drainages, vertical borehole drainage, and gob gas venthole drainage, have been developed and applied for CMM drainage.…”

“…1,6 Among these techniques, in-seam methane drainage in mining panels via horizontal borehole from underground entries is one of the most widely used methods in China because of its low cost and higher efficiency. 8,13,14 Therefore, how to design a proper borehole arrangement for panels to degas CMM at a specific drainage duration becomes extremely important for mining management. Generally, the more the number of the drainage boreholes, the closer the space among boreholes, the higher the gas drainage efficiency and the shorter the drainage time.…”

Evaluation of plow system performance in long-wall mining method using particle flow code

“…According to the importance of the coal production, many researchers try to investigate the various aspects of this subject (Cheng et al 2015;Hejmanowski 2015;Ju et al 2019;Fan and Ma 2018;Wirth et al 2018;Zhuravlev and Porokhnov 2019). Osterman (1974) compared the shearer and plow according to the seam properties, equipment, advance rate, etc.…”

Exploitation Contradictions Concerning Multi-Energy Resources among Coal, Gas, Oil, and Uranium: A Case Study in the Ordos Basin (Western North China Craton and Southern Side of Yinshan Mountains)

“…Gas explosions are the leading cause of deaths in coal mining activities. In recent years, practitioners have explored numerous methods to solve this problem and to take advantage of this mutualistic resource of coal; fortunately, there is a new measure called Integrated Coal Production and Gas Extraction, which will be discussed in the following sections [6][7][8].…”