RU2372487C1 - Method of degassing coal bed - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: method relates to mining particularly to coal mining and cn be used for working with a coal bed. The invention includes driving of a mine working, drilling of bed wells in the working area contour and down holes over the contours of prospective workings, sealing of wells/well, fluid injection into the bed through the holes over the limits of the bed discharge zone by stages, first in a static mode and then in a pulse mode, crack opening in the coal seam and connecting the wells/well to a degassing pipeline. Novelty of the invention is in the fact that a vibrowave generator is introduced into the well and in a static mode crack opening of black coal is performed at pressure of 3-5 MPa, anthracites - 5-8 MPa, after which the fluid is injected in a cyclic-pulse mode under pressure which provides penetration of the shock waves into interpore space and opening of macro- and micropores.

EFFECT: positive effect is achieved by intensifying underground degassing of the coal bed by providing penetration of the shock waves into interpore space and opening of macro- and micropores which will improve efficiency of removing methane from the bed, reduce gas content in the mine workings and reduce chances of explosions of gas and coal dust.

3 cl, 3 dwg

Description

The invention relates to mining and can be used to prepare coal seams for mining in conditions of their high gas content in order to intensify the degassing process and reduce the gas mobility of mine workings, to combat sudden emissions of gas and coal, to reduce the likelihood of gas explosions and coal dust.

A known method for the development of gas deposits, which can be used in the extraction of methane from coal seams, providing an increase in the extraction of methane from a coal seam during its commercial production.

The method involves the transition of gas from the bound state of a solid solution to a free gaseous state in the formation due to exposure to the formation by vibrations of an electromagnetic type emitter located in the well.

Exposure to vibrations is carried out in five stages. At the first stage, they act on a 2–25 MHz frequency on supersorption particles of coal substance. At the second stage, they act on a frequency of 0.7 MHz on the sorption particles of coal. On the third - with a frequency of 10-100 MHz for exposure to macropores of coal. In the fourth - with a frequency of 1 GHz to affect the mesopores. At the fifth - with a frequency of 88 GHz for exposure to micropores of coal [1].

The disadvantage of this method is the length of the degassing time, since exposure to vibrations is carried out in five stages. In commercial methane production, wells drilled from the surface are predominantly used. To increase methane extraction, these wells require careful cleaning of constantly arriving groundwater, which also requires additional time.

There is a method of preventing gas-dynamic phenomena during preparatory workings, which can be used in coal mining, methane extraction and ensuring safe working conditions for miners.

The method consists in acting on the resonant frequency of the rock mass using a special device that is lowered into the well with water, while the well is drilled into the production soil. Using a varying degree of immersion of the device in the well, the frequency of impact on the array changes [2].

The disadvantage of this method is the low energy impact on the array, especially in the conditions of rapid movement of the mine working at a high load on the face, developing coal seams hazardous for gas and dust, especially in conditions of deep occurrence from the earth's surface, where the permeability of coal and gas recovery are very low and, naturally, low degassing efficiency. Moreover, it is difficult to determine the resonant frequency of the rock mass during the immersion of the device in the well, since the rock mass is heterogeneous.

The closest in technical essence and the achieved result for the purpose of increasing the load on the working face and the speed of the preparatory workings during the development of high-gas coal seams underground method is the method of degassing a coal seam, including excavation of mine workings, conducting formation wells in the contour of the extraction section and downhole wells for the contours future workings, well / well sealing, injection of fluid into the formation through the wells outside the formation discharge zone poet apnea, first in a static and then in a pulsed mode, opening cracks in a coal seam and connecting a well / wells to a degassing pipeline [3].

This method has the following disadvantages. The use of an energy-generating system as a working fluid, during transportation of which it is necessary to accompany a police unit. Significant material costs are required per exposure. Using this system does not allow the removal of methane gas from macropores, the content of which reaches 30%.

The method is aimed at expanding and multiplying cracks.

In cracks, the sorption volume of methane is in the range of 16-18%, in macropores - 27-30%, the rest is much larger (more than half), the volume of methane is contained in micropores.

Most explosions of methane-dust mixtures in coal mines occur when the content of the microcomponent of the fusinite group in coal seams is from 13 to 32% with a yield of volatiles of 12–38%. Sorption methane consumption with a high content of fusinite increases and vitrinitis decreases.

Coals enriched with fusinite contain a large amount of methane. These coals in the process of destruction with a large number of dust fractions have the highest kinetics of gas recovery in the entire metamorphic series of coals, which is due to the presence of a large number of macro- and micropores in fusinite.

The aim of the invention is to increase the safety of underground work due to a more complete removal of gas from macro- and micropores and to reduce the degassing time in workings with a high load, especially in conditions of deep bedding of coal seams from the earth's surface, where the gas evolution rate is very low.

According to the invention, this problem is solved by the fact that in the method of degassing a coal seam, including sinking of mine workings, conducting formation wells in the contour of the excavation section and downhole wells for the contours of future workings, sealing the wells, injecting and replenishing fluid into the formation through the wells outside the zone of discharge of the formation stage by stage, first in the static and then pulsed modes, the opening of cracks in the coal seam and the connection of the wells to the degassing pipeline, a vibrating microwave generator is introduced into the well, In the static mode, coal cracks are opened depending on their strength at a pressure of 3-5 MPa, anthracite - 5-8 MPa, after which the fluid is pumped in a cyclic-pulse mode under pressure, ensuring the penetration of shock waves into the inter-pore space and the opening of macro and micropores. Liquid injection in a cyclic-pulsed mode of exposure to formations with a yield of volatile substances of 15-40% is carried out at a pressure of 8-10 MPa, and with a yield of volatiles of less than 15% and more than 40% under a pressure of 10-12 MPa, while on formations with with a volatility yield of 12-38% and a microcomponent of the fusinite group 13-32% are produced under a pressure of 9-10 MPa.

The invention is illustrated by drawings, where figure 1 shows the distribution of pores depending on the degree of metamorphism of coal (yield of volatile substances); figure 2, 3 shows a schematic diagram of the location of the downhole wells and paired retraction and overlying (parallel) workings, as well as horizontal degassing wells, respectively, in the process of driving the workings.

The method is as follows.

The volume of macropores (figure 1, 1 (•)) is of greatest importance for weakly metamorphosed coals. For fossil fuels, grades D and G are on average 0.06-0.03 m ³ / t; for fossil fuels, grade OS decreases to 0.016 m ³ / t with a yield of volatiles of 12-20%. With a further increase in the degree of coal metamorphism, the volume of macropores in average values again increases, reaching 0.029 m ³ / t for anthracites.

If for coals of grades D and G the volume of macropores exceeds the volume of micropores (Fig. 1, 2 (+)), then for coals of grades from G to G (V ^daf 40-21%) these volumes are approximately equal, and for more metamorphosed coals the volume micropores exceed the volume of macropores by 1.5-2.0 times.

In the process of driving development 1, i.e. at the very beginning of cutting the first or next excavation field (Fig. 2), conduct downward formation wells 2 beyond the contours of the future / future withdrawal 3 and overlying (parallel) 4 workings (depending on the technological scheme of the development of the formation - the extraction field).

From the moment of connecting the descending wells 2 to the pipeline 5 with the effect on the pores in a cyclic-pulse mode, they proceed to the next stages of processing the array, which are as follows.

Before starting the workings of the workings 3 'and 4', horizontal wells 6 are made, the number of which depends on the gas content of the formation, for example, three wells, two of which pass along the longitudinal axis of the workings, and the third - between them (Fig. 3); either three wells contouring the workings, or five wells, which are a combination of the previous scheme. The sequence of drilling of these horizontal wells is from bottom to top. In this case, the processes of drainage and degassing of the formation in the excavation field and in front of the passable workings are intensified due to the removal of fluid (water) through the wells. Then, the wells 6 are connected to the degassing pipeline 5, having previously introduced a vibrating microwave generator into the well or into the casing, and they act on macro- and micropores.

To increase the degassing coefficient and reduce gas accumulation when driving the recoil and parallel workings 3 and 4 outside the zone of influence of horizontal wells 6 (along their length), advanced degassing wells 7 are carried out (Fig. 3). These advanced wells, as well as horizontal wells 6, contribute to the removal of water from the degassed array and the intensification of the degassing process (wells 6 - the underlying excavation field, and wells 7 - the overlying one). Thus, wells, both horizontal and advanced, are located with the possibility of removing water inflows.

Coal cracks are opened at a pressure of 5-8 MPa, anthracite - 8-10 MPa. When working out “weak” coals with a strength coefficient of 0.4-1.0 (according to M.M. Protodyakonov) crack cracking in a static mode and a pulsed (not cyclical) effect on pores with the help of a vibrating microwave generator is possible. When mining hard coals with f = 1.0-2.0, the injection and recharge of fluid into the reservoir is carried out in a cyclic-pulse mode, necessary for the disclosure of macro- and micropores. In the process of cyclic-pulse exposure, the cyclicity will depend on the properties of the coal mass and mining conditions of the formation.

Liquid injection in a cyclic-pulsed mode of exposure to formations with a yield of volatile substances of 15-40% is performed at a pressure of 8-10 MPa, and with a yield of volatiles of less than 15% and more than 40% under a pressure of 10-12 MPa, while on formations with with a volatility yield of 12-38% and a microcomponent of the fusinite group 13-32% are produced under a pressure of 9-10 MPa.

The implementation of the method will increase the degassing coefficient at great depths from 0.1-0.15 to 0.45-0.5 and even higher, since in the macro- and micropores the sorption volume of methane is in the range of 27-29% and 53-56% respectively, while in cracks - 16-18%.

Information sources

1. RF patent No. 2239054 C1, IPC ⁷ ЕВВ 43/16. “A method for developing a gas deposit”, 2004, Bull. No. 30.

2. RF patent No. 2131517, 6 E21F 5/00. “A way to prevent gas-dynamic phenomena during preparatory workings”, 1999, Bull. No. 16.

3. RF patent No. 2166637, C2 7 E21F 7/00. "A method of preparing coal seams for mining", 2001, Bull. No. 13 (prototype).

Claims (3)

1. A method of degassing a coal seam, including drilling a mine, conducting formation wells in the contour of the extraction section and downhole wells for the contours of future workings, sealing the wells, injecting and replenishing fluid into the formation through the wells outside the discharge of the formation, in stages, first in static and then in pulse modes, opening cracks in the coal seam and connecting the well (s) to the degassing pipeline, characterized in that a vibrating microwave generator is introduced into the well in the static mode Coal cracks are hidden depending on their strength at a pressure of 3-5 MPa, anthracite - 5-8 MPa, after which the injection of liquid is carried out in a cyclic-pulse mode under pressure, providing the disclosure of macro- and micropores. 2. The method according to claim 1, characterized in that the injection of fluid in a cyclic-pulse mode of exposure to formations with a yield of volatile substances of 12-40% is carried out under a pressure of 8-10 MPa, and with a yield of volatile substances of less than 12% under a pressure of 10 -12 MPa. 3. The method according to claim 1, characterized in that the injection of liquid in a cyclic-pulse mode of exposure to coal seams with a volatiles yield of 12-38% and a microcomponent of the fusinite group of 13-32% is produced under a pressure of 9-10 MPa.

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