Abstract:The co-mining of
coal and gas is the inevitable future direction
of the mining of coal resources. Taking coal mining and gas extraction
as the two subsystems of the coal and gas co-mining system, to reveal
the mechanism of action between coal mining and gas extraction is
the premise of orderly co-mining. On the basis of a similar simulation
experiment of coal and gas co-mining, by obtaining the gas migration
law during the mining process and collecting a large amount of data
on the coal production and gas extr… Show more
“…Proceeding from the experience of practical working in mine conditions allows for concluding that the quality of the normative forecast turned out to remain low. In most scientific works, two-dimensional curves or their aggregates in the form of projections on a two-dimensional plane are mainly considered [70][71][72][73]. For example, a two-dimensional curve characterized by the relationship between the methane concentration and distance S at different times, as well as the methane concentration change over time at different positions, is insufficiently representative (see Figure 2 in [26]) owing to the deformation of a three-dimensional surface when it is projected onto a two-dimensional plane.…”
Decarbonization of the mining industry on the basis of closing the energy generation, on the basis of cogeneration of coal mine methane, and on the internal consumption of the mine is a promising direction in ensuring sustainable development. Known problems of deep underground mining do not allow for realizing the potential of man-made gas reservoirs due to the deterioration of the conditions of development of reserves of georesources. The aim of the work was to improve recommendations for the substantiation of drilling parameters for undermined drainage boreholes for increasing methane production from unconventional coal-gas collectors. The authors’ approach innovation lies in the possibility of using the established patterns of better natural stability of undermined boreholes to optimize them as spatial orientation parameters in an existing drilling passport for the improvement of methane extraction productivity. For this purpose, smoothing (LOESS) of the experimental data of two similar types of wells was used; then deterministic interpolation methods in combination with a three-dimensional representation of the response function in “gnuplot” were used. As a result, it was found that the increase in the inclination angle from 40° to 60° leads to a significant transformation of the model of the studied process, accompanied by a decline in the dynamics of methane emission and a decrease in the distance of the productive work zone of this type of well from 13 to 5 m before the roof landing, which then is replaced by a sharp increase in the productive work zone up to 35 m ahead of the longwall face. This allows under specific conditions for recommending increasing the productivity of methane capex from technogenic disturbed coal-gas reservoir replacement of wells with a smaller angle of rise to the transition to a more frequent grid of clusters from wells #4.
“…Proceeding from the experience of practical working in mine conditions allows for concluding that the quality of the normative forecast turned out to remain low. In most scientific works, two-dimensional curves or their aggregates in the form of projections on a two-dimensional plane are mainly considered [70][71][72][73]. For example, a two-dimensional curve characterized by the relationship between the methane concentration and distance S at different times, as well as the methane concentration change over time at different positions, is insufficiently representative (see Figure 2 in [26]) owing to the deformation of a three-dimensional surface when it is projected onto a two-dimensional plane.…”
Decarbonization of the mining industry on the basis of closing the energy generation, on the basis of cogeneration of coal mine methane, and on the internal consumption of the mine is a promising direction in ensuring sustainable development. Known problems of deep underground mining do not allow for realizing the potential of man-made gas reservoirs due to the deterioration of the conditions of development of reserves of georesources. The aim of the work was to improve recommendations for the substantiation of drilling parameters for undermined drainage boreholes for increasing methane production from unconventional coal-gas collectors. The authors’ approach innovation lies in the possibility of using the established patterns of better natural stability of undermined boreholes to optimize them as spatial orientation parameters in an existing drilling passport for the improvement of methane extraction productivity. For this purpose, smoothing (LOESS) of the experimental data of two similar types of wells was used; then deterministic interpolation methods in combination with a three-dimensional representation of the response function in “gnuplot” were used. As a result, it was found that the increase in the inclination angle from 40° to 60° leads to a significant transformation of the model of the studied process, accompanied by a decline in the dynamics of methane emission and a decrease in the distance of the productive work zone of this type of well from 13 to 5 m before the roof landing, which then is replaced by a sharp increase in the productive work zone up to 35 m ahead of the longwall face. This allows under specific conditions for recommending increasing the productivity of methane capex from technogenic disturbed coal-gas reservoir replacement of wells with a smaller angle of rise to the transition to a more frequent grid of clusters from wells #4.
“…where c s is the volume fraction of component s; D s is the diffusion coefficient, m 2 /s; and S s is the mass of the component produced by the chemical reaction per unit time, kg/(m 3 •s). 4 Considered the extraction area as a porous medium and add momentum sources, which included viscous loss term and inertial loss term.…”
Section: Boundary Conditions and Parameter Settingmentioning
confidence: 99%
“…This led to frequent gas overrun problems in the return airway and upper corner. It hindered the safety production of the mine [3][4][5]. The concentration of gas extracted during coal mine production is less than 30%.…”
To study the law of gas transportation in mining areas, Fluent numerical simulation software was applied to examine the influence of different pseudo-slope lengths (PSL) on gas concentration in a U-ventilated working area under no-extraction conditions. Based on this, numerical simulation experiments were conducted on the buried pipe extraction arrangement parameters. The simulation found that when there was no extraction, the PSL had an impact on the airflow in the extraction area, which caused the airflow in the extraction area to be disordered, causing gas to accumulate locally at the working area. When the buried pipe depths (BPDs) and PSLs of the working area worked together, the gas concentration of the working area was lower when the inlet air influence zone and the extraction influence zone were through; otherwise, gas concentration accumulation occurred at the working area. The research results showed that when the PSL was at 25 m and BPD was at 20 m, the gas concentration at the working area was not abnormal, and the gas concentration in the upper corner was lower. By adjusting the PSL and BPD of the test working area, the maximum gas concentration in the upper corner was reduced to 0.46% and the maximum gas concentration in the return air outlet was reduced to 0.41%. The experimental and practical results provide important reference values for coal and gas co-mining.
“…In addition, with the increase in coal mining depth and mining intensity, in the process of coal mining, the gas in adjacent layers or surrounding rock enters the work plane through mining fissures. The gas in the upper corner of the work plane easily causes the gas concentration in the return air flow to exceed the limit, which affects the safe mining of the work plane [8,9]. Former research has shown that a rock drainage roadway and high-level directional extraction borehole can effectively extract gas in the fissure zone and have great operational stability in the upper corner of the goaf and return air flow [10][11][12][13].…”
The technical principle of gas drainage using high-level directional extraction boreholes was analyzed. A range of overburden strata was stimulated for pressure relief during mining, the effects of different borehole parameters on gas flow in the goaf and gas concentration in the upper corner were compared, and a field test was conducted to analyze the effect and peculiarities of gas drainage. With the mining of the work plane, overburden mining fissures gradually develop forward and upward, showing a “saddle” shape along the coal seam. The fissures in the middle zone of the goaf are gradually compacted, and a gas accumulation zone is formed around the goaf. High-level directional extraction boreholes arranged in an ellipsoidal belt at the side of the air return can achieve efficient gas extraction in the roof fissure belt. Numerical simulation results showed that the height of the fully depressurized area was 65 m from the roof of the coal seam. In addition, three high-level directional extraction boreholes were drilled in the roof of the coal seam. The gas extraction concentration and gas extraction pure volume of these three boreholes first increased, then decreased, and finally tended to be stable. The sequence of their average values was borehole No.2 > No.3 (twice as much) and > No.1 (2.7 times as much), which are closely related to the evolution law of overburden mining fissures. The research results can provide a reference for the further study of gas extraction technology using high-level directional extraction boreholes in coal and gas outburst seams.
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