RU2495251C1 - Method for development of series of contiguous coal beds - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: method consists in identification of a length of active gas release zones, preparation of extraction pillars by tunnelling and strengthening mines in the rock massif, mining of extraction pillars and removal of methane in degassing wells. At the same time the length of active gas release zones is defined by variation of volume deformations of rock massif. At the same time the values of volume deformations of rock massif are produced by numerical methods on the basis of analysis of components of deformation and stress tensors with account of the time factor. The tensor characteristic is gas permeability of rocks under conditions of their natural occurrence. Medium values of rock massif gas permeability are assessed by the given mathematical expression. After determination of length of active gas release zones, with account of produced data, schemes of well drilling, their diameter and number are selected.

EFFECT: increased efficiency of methane removal, higher load at a working face and increased safety of clearing works by gas factor.

6 dwg

Description

The invention relates to mining, in particular to systems for the development of close-packed high-gas coal seams, and can be used to increase the load on the face and increase the safety of mining operations on the gas factor.

A known method of degassing coal-bearing strata (RF patent No. 2103516, E21F 7/00, publ. 01/27/1998). The method of degassing the coal-bearing stratum involves driving a drainage mine in the roof and soil of the gas-bearing formation before starting preparatory workings on the protected formation and installing temporary support in the mine. Drainage workings are carried out at a distance from the protected formation, not exceeding 8.5 times the width of the drainage workings. A perforated gas pipeline is laid on its soil, then the excavation is collapsed, and the excavation of the preparatory excavations on the protected formation begins after the gas content of the degassed section decreases to a safe level.

The disadvantage of this method is the low efficiency of methane removal, which reduces the possible load on the face and the high risk of treatment due to the influence of the gas factor.

A known method of degassing coal-bearing strata (RF patent No. 2382882, E21F 7/00, publ. 02.27.2010). The method includes driving a drainage mine through a gas-bearing formation-satellite at a distance from the protected formation before the start of preparatory workings on the protected formation. Pass it in a plane parallel to the boundaries of the excavation column in the area bounded by the lines of actual fault angles and displacement angles directed from the soil side of the workings of the protected formation. It is used as a degassing pipeline, aired separately due to shaft depression, and the maximum height h between the satellite formation and the protected formation is taken to be less than 40 m vertically. The minimum power of the satellite formation is taken more than 0.2 m, where m is the power of the protected formation.

The disadvantage of this method is the low efficiency of methane removal, which reduces the possible load on the face and the high risk of treatment due to the influence of the gas factor.

A known method of integrated development of a coal field (RF patent No. 2370649, E21C 41/18, E21B 43/295, publ. 07.04.2008). A method for the integrated development of a coal deposit section includes: preliminary degassing of the seams, opening and preparing the mine field by conducting a network of openings and preparing mine workings with a general bias towards the main shafts for organizing gravity drainage, supplying the necessary amount of air for their forced ventilation in one direction, excavation coal and transport of chipped coal to the surface along the same mine workings. As the development of coal mining develops, part of the mine workings in the worked out part of the mine field continues to be maintained until the end of its mining. After the extraction of coal in the mine field is carried out underground burning of security pillars, operational losses and substandard coal reserves. After coal burning in the mine field, the remains of the gaseous products of underground combustion are concentrated on the upper horizon of the mine field by filling the entire worked out space with an aqueous solution of reagents. Gaseous products of underground combustion are captured on the upper horizon of the mine field and, after extinguishing the source of underground burning, the productive solution is pumped out from the sump of the mine shaft. The productive solution is directed to the extraction of valuable and (or) toxic elements, moreover, filling the worked out space with aqueous solutions of reagents and pumping them out repeatedly if the reagent needs to be changed.

The disadvantage of this method is the low efficiency of methane removal, which reduces the possible load on the face, and the high risk of sewage treatment due to the influence of the gas factor.

A known method of developing suites of close-packed high-gas coal seams, adopted as a prototype (RF patent No. 2282030, Е21С 41/18, E21F 7/00, publ. 08/20/2006). A method of developing a retinue of converging high-gas-bearing coal seams involves mining one of them first and including preparing excavation columns by holding and securing conveyor and ventilation openings with leaving a coal pillar between the conveyor mine of the excavated mining column and the ventilation mine of the excavation column to be mined, conducting ventilation failures between the conveyor mine mined excavation column and ventilation development of the subject the excavation of the excavation column, the development of each excavation column with the simultaneous installation of the guard lining in the part of the conveyor excavation supported by the mining face at the boundary with the worked out space and erection of lintels in the ventilation faults from the worked out space and ventilation of methane from the worked out space using a methane-air mixture flow, created by air leaks carried out from the face through the mined-out space due to the mine depression in the sub the liveable part of the conveyor mine and refreshed along it, and divided into two parts at the ventilation fault closest to the bottom of the mine, one of which follows this fault and then along the ventilation output, as an outgoing excavation site with refreshment along it, and at the same time with methane removal by means ventilation remove it from the worked-out space by means of degassing by capturing another part of the methane-air mixture flowing through the worked-out space near the support part of the conveyor mine, through the degassing wells drilled into the mined mass from the ventilation mine towards the mined space, and according to the invention, the length of the active gas emission zones of the mined and mined adjacent coal seams is initially determined, and then, as the mining column is mined behind the treatment face in the conveyor mine in the zones of active gas evolution of undermining and undermining adjacent coal seams, a gas collecting stake is being built the lecturer by alternately erecting two transverse jumpers, the ends of which extend beyond the conveyor output circuit, each of the transverse jumpers being erected from the mined space in front of the next ventilation fault after being ahead of the treatment face of the next ventilation fault while zapping the ventilation fault located between the previously constructed and jumpers adjacent to it, closest to the face, while the jumper closest to the face the azo-collecting collector is placed from it at a distance equal to no more than the length of the active gas evolution zone of the worked-out adjacent coal seams, and another jumper, more remote from the working bottom, respectively, at a distance equal to no more than the maximum active gas-emission zone of the worked-out close coal seams, and as you move face, the removal of methane from the worked out space by means of degassing takes place in two stages: first, part of the methane-air stream the mixture, which follows the worked out space near the unsupported part of the conveyor output, is pushed out in the zone of influence of each of the transverse bridges of the gas collecting manifold in the direction of the arrangement of the upper layers of the unloaded zone of the worked-out adjoining coal seams, due to which there is an abrupt increase in the concentration and flow rate of the methane-air mixture of this part of the stream which is then bottled through degassing wells, and when drilling these wells into the undermined array from ventilation they are oriented in such a way that each bush of degassing wells is in the zone of influence of the transverse jumper of the gas collector, then, after moving the working face during mining of the extraction column, the cycle of work on constructing the next gas collector is repeated using the next erected jumper closest to the working face so that a jump in the concentration and flow rate of the methane-air mixture again forms with its subsequent trapping from the mined-out space with the help of the mentioned degassing wells, and after the preparation of the next excavation column in one of the suites of the adjacent high-gas-bearing coal seams and mining it in the suite, the first in the mining or underworking zone is to work out the adjacent adjacent coal seams using traditional development methods used in conditions of negligible residual natural gas content of coal seams.

The disadvantage of this method is the low efficiency of methane removal, which reduces the possible load on the face, and the high risk of sewage treatment due to the influence of the gas factor.

The technical result of the method is to increase the efficiency of methane removal, increase the load on the working face and increase the safety of treatment work on the gas factor.

The technical result is achieved by the fact that in the method for developing suites of closely-spaced high-gas-bearing coal seams, including determining the extent of zones of active gas evolution, preparing extraction columns by conducting and securing conveyor and ventilation openings over a rock mass, mining mining columns, methane removal from degassing wells according to the invention, the length zones of active gas evolution is determined by the change in volumetric deformations ΔΘ of the rock mass using the dependence:

ΔΘ = Θ ₀ -Θ _i ,

where: Θ ₀ - volumetric deformations of the rock mass before mining excavation columns; Θ _i -volume deformations of the rock mass at the i-th stage of mining mining columns, strain values Θ ₀ and Θ _{i of} the rock mass are obtained by numerical methods based on the analysis of the components of the strain tensors and stresses taking into account the time factor, and the gas permeability of rocks is a tensor characteristic in the conditions of their natural occurrence, and to assess the average values of gas permeability values k _cp rock mass using the expression:

; $$k_{\mathrm{from}R}={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}+a\cdot {\sigma }_{\mathrm{from}R}$$

;

- средние значения величин газопроницаемости массива горных пород при наличии массиве горных пород условия σ_ср→0, σ_ср - средние действующие напряжения в отрабатываемом массиве горных пород, кгс/см²; a - эмпирический коэффициент, при этом после определения протяженности зон активного газовыделения с учетом полученных данных выбирают схемы бурения скважин, их диаметр и число.Where: $${\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}$$

- the average values of the gas permeability of the rock mass in the presence of a rock mass conditions σ _sr → 0, σ _sr - average current stresses in the worked out rock mass, kgf / cm ² ; a is an empirical coefficient, and after determining the extent of the zones of active gas evolution, taking into account the data obtained, well drilling patterns, their diameter and number are selected.

The method is intended primarily for mining suites of high-gas-bearing coal seams with modern mechanized complexes. The development of coal-bearing strata, as a rule, is accompanied by large emissions of explosive and combustible methane gas, which during coal mining place restrictions on the load on the working face, the so-called gas ventilation barrier. Currently, due to the significant depth of mining operations, an increasing amount of methane is emitted (for example, the average gas content of the mines of the Donetsk and Karaganda basins is 30 and 90 m ³ / min, respectively). In many cases, it is impossible to deal with such amounts of methane in the traditional way (diluting methane with air and removing it from the mine with a ventilation stream) due to the need to supply an extremely large amount of air to the mine and exceeding the permissible speeds of its development according to the requirements of the current Safety Rules for the development of coal deposits. Increasing the speed of moving lavas on formations with high gas mobility and expanding the scope of applications of complexes with hydraulic supports require more effective measures to reduce gas mobility. Existing methods for preliminary degassing of developed formations by wells and increasing the degassing of worked out space often no longer provide a reduction in gas mobility to an acceptable level, since the largest amount of gas is released into the worked-out space from satellite layers.

Studies have shown that the extent of zones of active gas evolution can be carried out using calculation methods that take into account the change in the filtering ability of a rock mass (including a suite of high-gas-bearing coal seams) in the process of changing its stress state (redistribution of stresses in the rock mass). Such a value is a parameter characterizing the change in volumetric strain ΔΘ at a point in the rock massif, namely:

ΔΘ = Θ ₀ -Θ _i ,

where: Θ ₀ - volumetric deformations of the rock mass before mining excavation columns; Θ _i -volume deformations of the rock mass at the i-th stage, work out the mining columns.

The values of volumetric deformations of a rock mass can be obtained by numerical methods based on an analysis of the components of the strain tensors and stresses taking into account the time factor. To assess the gas permeability of the rock mass, depending on its mechanical condition, use the expression:

; $$k_{\mathrm{from}R}={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}+a\cdot {\sigma }_{\mathrm{from}R}$$

;

- средние значения величин газопроницаемости массива горных пород при наличии массиве горных пород условия σ_ср→0, σ_ср - средние действующие напряжения в отрабатываемом массиве горных пород, кгс/см²; a - эмпирический коэффициент. С учетом полученных данных выбирают схему и место бурения дегазационных скважин для эффективного удаления метана из свиты высокогазоносных угольных пластов.Where: $${\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}$$

- the average values of the gas permeability of the rock mass in the presence of a rock mass conditions σ _sr → 0, σ _sr - average current stresses in the worked out rock mass, kgf / cm ² ; a is the empirical coefficient. Based on the data obtained, a scheme and place for drilling degassing wells are selected for the effective removal of methane from the formation of high-gas coal seams.

The total porosity of coals on average can reach ~ 12%, but since it usually consists of sorption and filtering volumes, its last component (effective porosity) reaches ~ 3%. These volumes are usually represented by pores (cracks) with sizes from 10 ^-6 to 10 ^-1 cm, forming a complex system of interconnected transport channels (voids). The indicated values correspond to the condition when the rock mass containing the suite of high-gas-bearing coal seams is in a state unloaded from mechanical stresses (σ _cf → 0). Preliminary estimates showed that the presence of external loads corresponding to the geostatic field ("γ · H") to depths of ~ 1500 m does not significantly affect the change in the sorption volume of coal, which is mainly represented by ultrapores, and only changes their filtering porosity.

The study of the variability of the actual mining and geomechanical parameters of any evaluated object can be performed using the apparatus of the boundary element method, the finite element method, and others.

The technique for evaluating the stress-strain state (SSS) of a rock massif (MHP) developed for numerical experimentation allows one to obtain data on the parameter ΔΘ in the coordinate function (space). By setting some fixed (for certain time points) positions of the front of the treatment works, it is possible to obtain the functional dependence of the desired parameters on time for particular cases of considering the processes of deformation of the rock mass in a specific task.

The performed studies showed that there is a relationship between the effective porosity parameter "n" and the average values of stresses σ _cf acting in the rock mass. Therefore, in quasi-elastically deformable media, the interdependence of the parameters n and Θ _i is also obvious.

Θ _i = a · σ _cf.,

where: k - parameter (k = 3 / E · (1-2 · Θ · _i µ)); E is the modulus of elasticity of structural lithotypes of a rock mass; µ - Poisson's ratio of the same elements of the rock mass.

This allows you to determine the role of VAT rocks in changing the indicator of their effective (filtering) porosity, that is, the gas permeability of the medium can be expressed as follows:

; $$k_{\mathrm{from}R}={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}+a\cdot {\sigma }_{\mathrm{from}R}$$

;

- средние значения величин газопроницаемости массива горных пород при наличии массиве горных пород условия σ_ср→0, σ_ср - средние действующие напряжения в отрабатываемом массиве горных пород, кгс/см²; a - эмпирический коэффициент.Where: $${\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}$$

- the average values of the gas permeability of the rock mass in the presence of a rock mass conditions σ _sr → 0, σ _sr - average current stresses in the worked out rock mass, kgf / cm ² ; a is the empirical coefficient.

The method of developing suites of closely related high-gas coal seams is as follows. Excavation columns are prepared by holding and securing conveyor and ventilation openings over a rock mass. Work out mining columns. Methane is removed by ventilation due to mine depression and through degassing wells. Before starting the preparatory work, the extent of the zones of active gas emission of coal seams is determined by calculation by changing the volumetric deformations ΔΘ of the rock mass based on the relationship of the reservoir and filtration characteristics of the rock mass with its mechanical state using the dependence:

ΔΘ = Θ ₀ -Θ _i ,

where: Θ ₀ - volumetric deformations of the rock mass before mining excavation columns; Θ _i - volumetric deformations of the rock mass at the i-th stage of mining mining columns.

The values of volumetric deformations Θ ₀ and Θ of the rock mass are obtained by numerical methods based on the analysis of the components of the strain and stress tensors taking into account the time factor, and to evaluate the gas permeability of the filter medium depending on its mechanical state, use the expression:

; $$k_{\mathrm{from}R}={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}+a\cdot {\sigma }_{\mathrm{from}R}$$

;

- средние значения величин газопроницаемости массива горных пород при наличии массиве горных пород условия σ_ср→0, σ_ср - средние действующие напряжения в отрабатываемом массиве горных пород, кгс/см²; a - эмпирический коэффициент. С учетом полученных данных выбирают схемы бурения скважин, их диаметр и число для эффективного удаления метана из свиты высокогазоносных угольных пластов.Where: $$k_0^{\mathrm{from}R}$$

- the average values of the gas permeability of the rock mass in the presence of a rock mass conditions σ _sr → 0, σ _sr - average current stresses in the worked out rock mass, kgf / cm ² ; a is the empirical coefficient. Based on the obtained data, well drilling patterns, their diameter and number are selected for the effective removal of methane from the formation of high-gas-bearing coal seams.

It should be noted that this technique can be used to calculate the filtration characteristics of the zones of the rock mass, experiencing only elastic deformations, i.e. for the zones of collapse and crack formation, other approaches must be used.

The implementation of the method for developing a suite of close-packed high-gas coal seams is illustrated by an example for the conditions of the Fourth seam of the Pechora coal basin. Fig. 1 shows a geomechanical model of a rock mass for assessing the stress-strain state of rocks in the "Fourth" rock mass produced by the formation; Fig. 2 shows a graph of the function k _cp = φ (σ _cf ) for evaluating changes in the gas permeability of the rock mass , Fig. 3 shows a fragment of the diagram of the domain of estimation of the parameter "ΔΘ" in the worked-out array "n ₁₁ -n ₇ ", Fig. 4 shows the zonality of the variability of the geomechanical and gas-dynamic properties of the worked-over interdomain "n ₁₁ -n ₇ ", "A", “B”, “C”, “G”, “D”, “E”, “F”, “3”, “B” and “A” - active zones of gassing in the rock mass, Figure 5 shows a graph of the function ΔΘ = f (Θ _i) for values of: Θ _Ao = -62 · 10 ^-5 (meets the conditions nadrabotki mezhduplastya "n ₁₁ -n _7"); Θ _Ao = -30 · 10 ^-5 - as a variant of the family ΔΘ = f (Θ _i ), Fig. 6 shows a variant of a degassing circuit for a workable inter-layer (n ₁₁ -n ₇ ) (gently laying bed "n ₁₁ ", descending order mining pillars).

In Fig. 1, the overwork zone corresponds to the limits of the area S _o (exposure area before the 1st landing of the main roof), S _II (exposure area until the next landing of the main roof), and the time factor is characterized as t → t ₁ , t _i ≥t _n (t is the time factor characterizing the time elapsed since the beginning of lava mining, t ₁ is the time factor characterizing the time during which the loaded mined space gains the maximum area before collapse, t _i is the time factor characterizing the time elapsed since the beginning of lava mining before reaching races etnoy zones A, B, ..., t _n - time factor characterizing the time elapsed from the beginning of lava before planting main roof). At the boundary of the studied weightless region, a pressure of P≈γH = 25 MPa was applied. The study zone of the parameters of the stress-strain state of the array: 0≤x≤160 (m), -1.6≤y≤-83 (m), which completely "covers" the workable thickness (including reservoir n ₇ ). "1-1" is the axis of symmetry.

For practical (approximate) estimates of the change in effective porosity in the array, a simple approximation of the function n = f (σ _cp ) can be used in the form:

; $$k_{\mathrm{from}R}={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}+a\cdot {\sigma }_{\mathrm{from}R}$$

;

- средние значения величин газопроницаемости массива горных пород при наличии массиве горных пород условия σ_ср→0, σ_ср - средние действующие напряжения в отрабатываемом массиве горных пород, кгс/см²; a - эмпирический коэффициент (~ 52·10^-4).Where: $$k_0^{\mathrm{from}R}$$

- the average values of the gas permeability of the rock mass in the presence of a rock mass conditions σ _sr → 0, σ _sr - average current stresses in the worked out rock mass, kgf / cm ² ; a is the empirical coefficient (~ 52 · 10 ^-4 ).

It should be borne in mind that stress values for the conditions σ _cf > 0 in the developed rock mass are limited.

The gas permeability of rocks in their natural occurrence is a tensor characteristic. A general idea of the variability of this parameter as a function of mechanical stresses in the massif can be made by analyzing the average (for a given point in the rock mass) parameter values, i.e. in the form k _cp = φ (σ _cf ).

(при σ→0) составляет около 60 µD при коэффициенте вариации V≤30% (≈0,06·10^-8 см²), а характер функции k_cp=φ(σ_ср) для всех исследованных типов углей может быть представлен в экспоненциальной форме.The results of studying the gas permeability of coal seams (IGD, MakNII) have shown that for coals of grades "K" - "G" parameter $$k_{}^{}$$$${}_0^{\mathrm{from}R}$$

(as σ → 0) is about 60 μD with a coefficient of variation V≤30% (≈0.06 · 10 ^-8 cm ² ), and the character of the function k _cp = φ (σ _cf ) for all types of coals studied can be represented in exponential form.

To assess the variability of gas permeability of the array "n ₁₁ -n ₇ ", produced by the reservoir "Fourth", in a first approximation, can be used approximation equations of the form:

; $$k_{\mathrm{from}R}={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}+a\cdot {\sigma }_{\mathrm{from}R}$$

;

- µD (для ориентировочных расчетов может быть принято 60 µD); 30≤ $$k_0^{ср}$$

≤65, a=104·10^-3.where: ± σ _cf - kgf / cm ² ; $$k_0^{\mathrm{from}R}$$

- µD (for approximate calculations, 60 µD can be taken); 30≤ $${\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="00000007.png,00000008.png"\; state="\{\{state\}\}">k</figure-callout>}}_0^{\mathrm{from}R}$$

≤65, a = 104 · 10 ^-3 .

The spread in the values of k _cp = φ (σ _cf ) when using the above dependence does not exceed 30%. The graph of the function k _cp = φ (σ _avg ) for assessing changes in the gas permeability produced by the “Fourth” inter-layer “n ₁₁ -n ₇ ” is shown in FIG.

Using the methodological approaches given above, we obtain the fields of increments (changes) in volumetric deformations in the form:

ΔΘ = Θ ₀ -Θ _i ,

where: ΔΘ is the change in volumetric deformations of the rock mass; Θ ₀ - volumetric deformations of the rock mass prior to the development of excavation columns; Θ _i - volumetric deformations of the rock mass at the i-th stage of mining mining columns (these states correspond to the schemes: A, B, C, G, D, E, F, Z, B, A, Fig. 4).

Information on the fields ΔΘ makes it possible to unambiguously (compared with the fields Θ) evaluate the geomechanical and gasdynamic state of the worked out rock stratum. Previously, the procedure for such an assessment was established, characterizing the “directivity” of changes in the reservoir properties of a rock mass depending on a change in ΔΘ. In particular, the growth of ΔΘ values modulo under conditions of compressed (but for Θ _i <θ _Aо ) or extended zones of the rock mass determines the "state" of the mass unloading when the condition ΔΘ <0 is fulfilled. This means that the "unperturbed" array (not worked out) is initially located in the compressed zone, i.e. the values are: Θ _Ao = -62 · 10 ^-5 , ΔΘ = 0. For other initial quantities Θ _Ao corresponding to the new zero value ΔΘ, the corresponding dependences ΔΘ = f (Θ _i ) will take place. For the conditions under consideration, in particular when Θ _Ao = -62 · 10 ^-5 , this dependence is shown in Fig.5.

As is obvious, the growth of positive values of ΔΘ (ΔΘ> 0) corresponds to the conditions of loading the array from state A ₀ .

An analysis of the fields ΔΘ showed the following. When the lava face moves away from the assembly hole to a distance of 40 m in lava soil rocks at depths from the first meters to twenty or more meters, the modulus of the Δ рост parameter grows (provided ΔΘ <0), which meets the conditions for unloading the rock mass, the latter at the indicated the area extends to depths from several meters to twenty (or more) meters, i.e. can reach the reservoir "n ₈ " (a significant part of the inter-reservoir "n ₁₁ -n ₈ " is unloaded). Given the technological parameters of production, this unloading will take place at a distance of up to ~ 30 m from the mounting chamber, i.e. ~ 10 days after the start of the primary movement of the face.

As the lava further moves away from the split furnace to a distance of 50–60 m, the discharge zone reaches a depth of thirty meters (“n ₁₁ -n ₈ ”), spreading over almost the entire area of the worked out space formed at the time point up to ~ 20-25 days. In the time interval (10–25 days), the modulus of the parameter ΔΘ continues to grow, and to the greatest extent within the interdimension "n ₁₁ -n ₁₀ ".

Further, up to a distance of about 300 m from the mounting chamber (time range up to ~ 90 days), an increase in / ΔΘ / is observed along the width of the worked out space at its greatest intensity along the sections of the worked out area adjacent to the excavation drifts (up to 30 m in plan). Taking into account the widely used method of working the pillars (along strike) in a descending order, it should be noted that in the case under consideration, the largest values of changes in the pore volume in the worked out rock stratum will take place (in addition to the near-track region) within the lower part of the worked out space, counting from the conveyor belt drift (at distances ~ (0.5 ÷ 0.7) L _l ). In depth, the unloading encompasses the inter-layer "n ₁₁ -n ₇ " - along the drift, changing to depths "n ₁₁ -n ₈ (n ₉ )" in the direction toward the center of the worked out one.

At distances from the installation chamber of more than ~ 300 m (up to ~ 400 m), the effect of elastic restoration of the bulk porosity of the rocks within the inter-layer "n ₁₁ -n ₈ " (up to ~ 30-35 m in depth) is retained in the developed layer. In time, this corresponds to the range (85 ÷ 90) - (110 ÷ 120) days.

Then (> 400 m), in the worked-out interdomain under the mined-out space, it begins and, by the time the lava leaves 600–700 m from the assembly chamber, the restoration of the initial pore space of the inter-reservoir rocks "n ₁₁ -n ₇ " (/ ΔΘ / → 0) almost ends . An exception is the near-track zone (up to ~ 20 m), in which there is a partial unloading of rocks in the inter-layer "n ₁₁ -n ₉ " (/ ΔΘ / ≠ 0). From the same distance (~ 600 ÷ 700 m) on the main area of the mined-out space, pressure is restored over the soil of the formation "n ₁₁ " (~ γ · Н), and, accordingly, the initial state (to the "disturbance" of the rock mass by the lava) is restored interdomain "n ₁₁ -n ₇ ", i.e. / ΔΘ / → 0. However, along the moving lava, rock unloading takes place in its soil: it is almost “full” at a depth of up to 10–15 m (“n ₁₁ -n ₁₀ ”) and partial (up to ~ 50%) at depths up to ~ 55 m (“n ₁₁ -n ₇ "), which is characterized by a rather large, and in the first case (" n ₁₁ -n ₁₀ "), a very sharp increase in the values of the modulus / ΔΘ / in approximately twenty meters of the VP zone, counting from the face of the lava. The beginning of the period under consideration in the time range corresponds to ~ 130 ÷ 140 days.

The established zoning of discharge of the rock stratum produced by the “n ₁₁ ” formation also determines a change in their effective porosity. The gas permeability of the rocks changes, which must be taken into account when choosing the degassing parameters of the inter-layer under consideration.

The distribution scheme of the said zones within the worked-out space of the excavation column, worked out along strike (in descending order), is shown in Fig. 4.

≈34 µD при соответствующем значении Θ_Ао=f(σ_ср), равном ~ (-62·10^-5).Changes indices (Δn - change in the effective porosity of the rocks,%; mean values of permeability k _cp rock mass%) are relative characteristics "unperturbed" cleaning groove array indexed "0 ^th" mark: n ₀ ≈1,7%; $$k_0^{\mathrm{from}R}$$

≈34 μD with the corresponding value Θ _Ao = f (σ _avg ) equal to ~ (-62 · 10 ^-5 ).

For practical (approximate) estimates of the change in effective porosity in the array, a simple approximation of the function n = f (σ _cp ) can be used in the form:

n = n ₀ + 52 · 10 ^-4 · σ _cf ,

where: ± σ _cf - kgf / cm ² ; n ₀ -% (~ 3%); 1.5≤n≤3.5 (%).

It should be borne in mind that the magnitudes of the stresses in the developed MHP are limited.

As the lava moves from the assembly chamber at a distance of up to 70 ÷ 80 m (i.e., after ~ 20 ÷ 25 days from the beginning of the treatment excavation), the unloading of the inter-layer "n ₁₁ -n ₇ " begins, accompanied by an increase in Δn and Δk _cp : from ~ 1 ÷ 2% to ~ 5 ÷ 30% in the depth region of the interdomain "n ₁₁ -n ₉ (n ₈ )" (zone "A", "B" of figure 4).

Further, at distances from 70 ÷ 80 m to 120 ÷ 150 m from the mounting chamber (zones "B", "C" of Fig. 4) in the soil in the region of the central part of the worked out space (and higher in the formation uprising), the Δn and Δk _cp : up to ~ 30% in inter-layer rocks "n ₁₁ -n ₉ " and up to ~ 10% in inter-layer "n ₉ -n ₇ ". The time for cleaning work at this moment is about 50 days.

In the zone from 120 ÷ 150 m to ~ 180 m under the central part of the airspace, a process of further decrease in Δn and Δk _cp values to values close to the background (unperturbed) state of the array occurs. In the zone "G" (in the diagram of Fig. 4), in the region adjacent to the conveyor drift in the inter-zone range "n ₁₁ -n ₈ ", the parameter values Δn and Δk _{cp are} characterized by values (5 ÷ 15%), and in the inter-region "n ₈ -n ₇ "- (2 ÷ 8%). In the direction of the longitudinal axis of symmetry of the airspace up to distances from the drift of ~ 0.33 L _l , respectively, in the above-mentioned packs, the parameters Δn and Δk _cp vary in the range: (15 ÷ 30%) and (2 ÷ 10%).

In the zone "D" (figure 4) at a distance of about 200 m from the mounting chamber (180 ÷ 200 m - about 60 ÷ 65 days of cleaning work) along the drift in the inter-layer rocks "n ₉ -n ₇ " the considered values vary from ~ 1% to ~ (7 ÷ 8%) (in the direction from the bottom up), and in the inter-layer "n ₁₁ -n ₉ ""to (10 ÷ 15%). At distances <0.33 L _L from the drift (in the direction of the center of the airspace), the changes in Δn and _cf , respectively, for the same interplasts, will be: (2 ÷ 10%) and (15 ÷ 25%).

The subsequent change in the reservoir properties of rocks in zones "E", "Zh" and "3" has a pronounced decrease in Δn and Δk _cp values both in the direction of lava movement from the assembly chamber and in the normal direction. In the first case, considering the inter-reservoir "n ₁₁ -n ₇ ", the indicated changes are from (2 ÷ 5%) (at a distance of ~ 200 ÷ 250 m from the installation workout at the time of ~ 70 days from the beginning of the excavation of the formation) to (1 ÷ 2%) (at a distance of ~ 550 ÷ 600 m from the installation workout at the time of about 180 days from the beginning of work on the extraction of the formation). In this case, the "lower" values (1 ÷ 2%) of the changes in effective porosity and gas permeability correspond to the pack of inter-layer rocks "n ₉ -n ₇ ", and the "upper" (2 ÷ 5%) - to the inter-layer "n ₁₁ -n ₉ (n ₁₀ ) ". Normally to the drift at a distance of ~ 0.2 L _l from it, under the worked-out space, approximately “background” characteristics of the previously developed inter-layer are restored. The considered state in the "near-track" zone remains stable and further (over 350 ÷ 400 m) along the worked out space up to the area "B" - "A" (Fig. 4) near the bottomhole space of the lava operating at the "current" time.

At the indicated distance (> 550 ÷ 600 m, i.e., at a time point of ~ 180 ÷ 200 days) in zone "B" - "A" (Fig. 4), the changes in the parameters Δn and Δk _cp remain further stable and are reversed when considered the departure of lava from the mounting chamber (zone "A" - "B" in figure 4). From a distance of 60 ÷ 70 m from the lava plane and further in the direction of its face, the following changes take place:

- in the interdomain "n ₉ -n ₇ " - a decrease in parameters from ~ 30 ÷ 5% to ~ 2 ÷ 1%;

- in the interdomain "n ₁₁ -n ₉ " - a decrease in parameters from ~ 60 ÷ 15% to ~ 5 ÷ 2%.

These changes do not apply to near-track, approximately twenty-meter zones, in which the conditions of the state of the massif of rocks of the interdomain are close to those in zone "Z", discussed above.

An analysis of the state and variability of the rock mass during its completion, performed by the ΔΘ factor, allows us to assess the state of the rock mass of the worked stratum, obtained on the basis of mainly the analysis of the fields ε _x and ε _y in the same zones . Using the above dependences, it can be used as a software product for obtaining initial data and developing methodological aspects of constructing degassing schemes for the rock massif worked out by the Fourth formation, taking into account the spatio-temporal variability factor of its reservoir properties. A possible scheme for drilling degassing wells (for the conditions of the considered example) is shown in Fig.6.

The use of this method of developing suites of closely related high-gas coal seams provides the following advantages:

- improving the efficiency of methane removal;

- increase the load on the face by the gas factor;

- improving the safety of treatment operations to the gas factor;

- reduction in the cost of coal mined.

Claims (1)

A method for developing a suite of closely-connected high-gas-bearing coal seams, including determining the extent of zones of active gas evolution, preparing extraction columns by conducting and securing conveyor and ventilation openings over a rock mass, mining mining columns, removing methane from degassing wells, characterized in that the extent of the zones of active gas evolution is determined the change in volumetric deformations ΔΘ of the rock mass using the dependence:
ΔΘ = Θ ₀ -Θ _i ,
where Θ ₀ - volumetric deformations of the rock mass before mining excavation columns; Θ _i - volumetric deformations of the rock mass at the i-th stage of mining mining columns,
the strain values Θ ₀ and Θ _{i of} the rock mass are obtained by numerical methods based on the analysis of the components of the strain and stress tensors taking into account the time factor, the tensor characteristic being the gas permeability of the rocks under their natural occurrence, and to estimate the average values of gas permeability k _{cf of} the rock mass rocks use the expression:
$$k_{\mathrm{from}R}=k_0^{\mathrm{from}R}+a\cdot {\sigma }_{\mathrm{from}R}$$

;
Where $$k_0^{\mathrm{from}R}$$

- the average values of the gas permeability of the rock mass in the presence in the rock mass of the condition σ _sr → 0; σ _cf - average effective stresses in the worked out rock mass, kgf / cm ² ; a is the empirical coefficient,
in this case, after determining the extent of the zones of active gas evolution, taking into account the obtained data, select well drilling patterns, their diameter and number.

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