SU1744271A1 - Method for degassing coal seams - Google Patents

Abstract

Usage: coal seam degassing during underground mining. The essence of the invention: the impact of vibration loads in the frequency range of 1000-1500 Hz, together with the injection of hot water into the reservoir with propping agents, induce acoustic cavitation in the reservoir and reach it to open cracks, pores of new cracks, desorption and changes in water and gas permeability. 2 hp f-ly, 2 ill.

Description

The invention relates to mining and can be used for the degassing of coal seams, controlling the condition and properties of rocks in an array when mining deposits by open or underground methods.

There is a known method of preventing coal and gas emissions, including drilling wells in the in-hole and along the length of the bottom, installing vibrators in them and affecting the array with a vibration-pulse load, where the control hole is drilled, the rate of gas release is set at intervals when drilling it, and the area of the maximum gas release rate is set each cycle, starting from the central part of the bottom, the wells along the bottom are drilled parallel to the axis of generation beyond the zone of maximum emission rate, while the vibrator is installed in the zone of maximum velocity The gassing spans produce a vibration-pulse load first in the wells located in the central part of the slaughter and then in the wells located throughout the bottom of the hole with frequencies of 0.5-0.8 the magnitude of natural oscillations.

The known method is laborious and low-tech, since installing the vibrator in the depth of the well is very labor-intensive, the method does not allow to work in the selected frequency range and synchronize the work of the group of vibration sources, since they are percussion, i.e. the rock at the point of contact with the vibrator is destroyed, as a result of which elastic oscillations attenuate at a distance of 2-3 m from the vibrator, the efficiency of transfer of energy of elastic oscillations to rocks is low, and it is almost impossible to work in the selected frequency range.

The known method of coal seam degassing includes drilling wells on a degassing reservoir, loading a well with a cylindrical element from an expanding material during initiation, pre-moistening the coal seam, initiating expansion of the element with the initiation of elastic vibrations in the formation and the formation of new cracks.

The known method is laborious, low-tech, does not allow to conduct explosive work.

WITH

h

s s Yu

v |

without stopping the technological works, an explosion excites the frequency spectrum 10-100 kHz, i.e. the method is local - the first few meters, the explosion is not reproducible and requires a large amount of drilling holes.

The purpose of the invention is to reduce the outburst risk of a degassed coal seam by increasing the hydrotreatment uniformity due to the initiation of elastic waves in the formation in the range of 10-1500 Hz.

This is achieved by the fact that, according to the method of the well, the wells pitch 7–12 m, hot water is pumped into them with a temperature of 60–80 ° С and with the addition of 2–3% surfactant (surfactant), elements of magnetostrictive material, it is influenced by electrical voltage pulses with the formation of elastic waves; And when changing the compression strain in a layer on the tensile deformation - in dia pazone 1000-1500 Hz, while a vibration was stopped at the time to achieve a concentration of lava methane concentration equal to a vibration.

The vibration of the coal plasma is carried out at a minimum wave amplitude and gradually increases to a value equal to half the level of the fracture stresses

Water injection is carried out with the addition of 1-2% propping agents with particle sizes of 0.5-1.0 mm and density (2.6-3.2) - 106 g / m3.

FIG. 1 shows a scheme for implementing the method; in fig. 2 shows section A-A in FIG. one.

The method is carried out as follows.

In the development 1, which was traversed in the mountain massif 2 and adjacent to the formation 3, the drilling of the well 4 with a depth of 3-5 m and a diameter of 200-300 mm is filled with 2/3 of their volume with rare-earth substance 5, which has a giant magnetostriction. Electrodes 6 are inserted into it and connected to the pulse voltage source 7. The magnitudes and principal stress vectors are preliminarily determined in specially drilled holes, and then equipment is placed in these holes to monitor the stress-strain state of the rocks in the massif before, during and after vibrating in the coal seam 3. Then in the direction of one of the principal stresses are drilled along the bottom coal

the formation of the well 8, sealed them and connected to the hydropulsator 9. The element is a cylindrical body of magnetostrictive material, which is used rare-earth substances 5 or their compounds with the addition of 7-10% in the binding quick-hardening cement. progressive movement relative to

0 the borehole axis when applying the pulse voltage from the source 7, and the frequency, intensity and duration of the excited elastic waves are controlled by changing the magnitude of the pulse voltage and its

5 parameters - frequency and duration. The wells 4 are drilled at a distance from each other of -3 wavelengths of the main frequency emitted at a frequency of 1000 Hz and a P-wave speed in nnacie 2000 m / s, the wavelength is 2

0 and i.e. boreholes 4 are drilled at a distance of C-10 meters from each other. This is because at such distances the field of elastic stresses from the source is evenly distributed, While at a distance equal to or less than the wavelength, it is uneven.

The time effect is to bring the mountain massif into a non-hazardous state during synchronous operation of a group of sources, which is controlled by means of electronic

0 console / level 10, depends on the formation water-cut and rock pressure — the weight of the overlying rocks. During synchronous operation, the group of Yutochnikes increases the amplitude of their oscillations from the minimum to maximally 5 levels, determined by the level of stress in a plasma that is equal to 0 5-0.6 from the discharges with such a condition as not to cause dynamic occurrences of mountain pressure. Hesitations cause in plazga

0 compression and expansion waves, and in the rarefaction zone of an elastic wave, fractures arise — tiny bubbles filled with gas and steam or their mixtures that rivet in the compression zone of the elastic wave. First, to bring the reservoir to an excited state and increase its hydra and aerodynamic properties, the reservoir is affected in the range of 10-1500 Hz and water is injected into the reservoir with surfactant additives

0 2-3% at temperatures up to 80 ° C in conjunction with propping agents with particle sizes of 0.5-1.0 mm and density of 2.6-3.2 g / m. Wedging agents that fall into the pores and fractures of the formation do not give them

5 close, serve as new stress concentrators and contribute to an increase in fracturing of the reservoir and host rocks. When the compression deformation is changed by tensile deformation — achieving optimal formation permeability — the vibratory effects are stopped and switched to a different frequency range (1000-1500) Hz for that , in order to initiate cavitating processes in the reservoir, with the collapse time of cavitating bubbles and their energy determined from the expressions

E

Ro | l: - R3 and

B-Nmin Ј- (Ј-1) -) + max L o

-4 (Ј-1) 1b

where Ј Ro / Rmin 10; p 2 106 g / m3; Рmax 100 MPa; RMHH 1 mm; R0 10mm.

We obtain that the energy E is 3.2–103 MPa per pulse and the collapse time is 2 10 3 s. Such impulse pressures cause powerful hydrodynamic disturbances in the form of compression pulses of micro- and macro-shock waves and fluid flows generated by pulsating bubbles. In addition, the collapse of bubbles causes a strong local heating, which in turn is accompanied by the decomposition of methane into atomic components, which have a greater penetrating and diffusive capacity, since coal and host rocks are a molecular sieve, in which they are redistributed. accumulations of methane due to vibrations and vibrations in the selected frequency range, and also due to the fact that surfactants perform the work of expansion forces in the reservoir, as a result of which the pores and cracks in it become communicating. As a result of the occurrence of cavitating processes, the formation is subjected to an intense impact, which is manifested in the destruction of individual coal packs and a change in the adhesion forces between them and its separate layers.

The work of a group of vibration sources is controlled by geomechanical and geophysical research methods. The formation is affected by vibration loads, its stress-strain state is measured, the concentration and rate of methane gas emission before, during and after vibratory exposure, these parameters are compared and judged by the degassing of the coal seam, which contributes a decrease in the dynamic manifestations of rock pressure to sudden emissions of coal, rock and gas, i.e. contributes to the effectiveness of the method.

After the required time has elapsed, the well 4 is drilled in another place, and the elements of the magnetotricion are removed by heating.

0

five

0 5 0 5 0

5 0 5

of the borehole material and used elsewhere, it is left in the old place if they can still be reused on the coal seam.

The essence of the method lies in the fact that under the influence of powerful vibration loads generated by vibration sources, a layer of compression and rarefaction waves appear in the formation. These waves cause the migration of fluid fluids and gas components that occur in the pores and fractures of the reservoir, and when the heated solutions in the reservoir are injected, cavitating processes take place that promote the redistribution of the elastic stresses in the reservoir, the outflow of gases from the pores and cracks, those. degassing of the reservoir due to compresses and vibrations and uncovering new pores and cracks when propping agents get into them. The degree of development of cavitation and the nature of its flow and the effect on the formation vary with gas content, hydrostatic pressure and temperature in the formation and causes asymmetry of the collapse process of cavitating bubbles and leads to its disintegration into many smaller others that serve as new germs of cavitating processes. In addition, as the distance from the source changes, the alternating pressure changes, which, in combination with the overpressure in the reservoir, creates opportunities for manifestation of cavitating processes.

The vibration effects of the proposed method allow the redistribution of stress-strain state of the reservoir to the spread of powerful vibration loads and migration of fluids; minimize the likelihood of occurrence of rock pressure dynamics; create conditions for increasing hydro and aerodynamic bonds in the formation; improve the efficiency of the degassing method.

The use of the invention significantly reduces the likelihood of sudden emissions of coal and gas and reduces the cost of maintaining rock pressure when mining lava compared to the classical methods of degassing coal seams that do not use vibratory effects in a selected frequency range.

The expected economic effect from the implementation of the invention is 43 thousand rubles. in year.

Claims (3)

1. A method for degassing coal seams, including drilling wells to a degassed reservoir, loading a well with a cylindrical element from an expanding material at initiation, pre-moistening the coal seam, initiating expansion of the element with the formation of elastic vibrations in the formation, and new cracks, o t so that, in order to reduce the out-of-danger of a degassed coal seam by increasing the hydrotreatment uniformity, the wells are drilled in increments of 7–12 m, they are injected hot water with a temperature of 60-80 ° C and the addition of 2-3% surfactants, an extended cylindrical element made of a magnetostrictive material is placed in the well, it is impacted by electrical voltage pulses to form elastic waves, and the strain is controlled in the reservoir compression and tension, control the rate of gas evolution from the reservoir, and first, the vibration effect is carried out in the frequency range 10-1000 Hz, and when changing in the formation deformations of compression on the strain deformation - in the range 1000-1500 Hz, with this, vibration is stopped when the concentration of methane in lava reaches the initial concentration of methane before vibration, 2. The method according to claim 1, wherein the fact that the vibration of the coal seam is carried out with a minimum wave amplitude and gradually increases to a value equal to half the level of destructive stresses, 3. The method according to claim 1, wherein the injection of water is carried out with the addition of 1-2% of propping agents with a particle size of 0.5-1 mm and a density of 2, 6-3, 2 106g / m3. Fig 2