RU2453704C1 - Method for determination of methane content in coal vein - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: consists in provision of methane drainage boreholes in plane of coal seam in the area of broken working, the measurement of firedamp flow from the wells and its methane content, determination of the data of seam gas recovery into the wells and the volume of methane recovered from it in the course of degassing. Additionally, in an idle shift the air flow is measured, as well its methane content at the gatehead, the outstretch of the zone unloaded of coal massif rock pressure in front of highwall mining and its methane reserves are set, the degree of seam degassing by wells and the natural degassing of unloaded coal massif are determined. Methane content in a coal vein in the area of coal extraction with cutter-loader is determined. In this respect, the degree of seam degassing by wells is determined by volumes of methane recovered and by its reserves in the area of the seam degassed by wells, and degree of natural degassing of unloaded coal massif in front of highwall mining - by the measured methane flow in the flow of air, by residence time of seam area and methane reserves in it. The volume of methane recovered from the seam in the area of preliminary degassing is determined using the rates of seam gas recovery into degassing wells.

EFFECT: providing the possibility of determining methane content in a coal vein in the area of coal extraction with cutter-loader.

4 cl

Description

The invention relates to mining and can be used as a starting value for assessing the effectiveness of degassing of developed coal seams and the intensity of methane release from them at the stage of forecasting methane abundance of the bottomhole space of the lava and excavation site.

A known method for determining the gas content of coal seams, which is used for exploration. The essence of this method is to directly determine the natural gas content of coal seams by drilling wells from the surface, sampling coal with a gas and gas intake, degassing flushing (drilling) fluid and a selected coal sample (core) [1].

The disadvantage of this method is the high complexity.

A known method for determining the natural gas content of coal seams according to gas surveys in mine workings of mines. The method consists in measuring the air flow in the mine network of mining sites, the methane content in it, establishing the gas balance of the mining site and then determining the methane content of the formation by calculation method [2].

The disadvantages of this method are the large volume of gas-air surveys and the low accuracy of determining the methane content of the formation.

A known method for determining the gas content of a coal seam, including measuring the gas evolution from a cavity in the formation in two stages based on measurements of the flow rate of the gas-air mixture, determining the residual gas content of the beaten coal, setting the gas recovery indicators for a cavity (well), and determining the gas content of the formation using calculation formulas [ 3].

The disadvantages of this method are the measurements in the conducted well in two stages, determination of the gas recovery parameters of the formation and beaten coal, the use of numerous formulas for calculating the source data, the low accuracy of determining the indicators included in the calculation formulas during the short duration of drilling sections of the well.

A known method for determining the gas content of a formation based on the selection of a coal-gas sample from an array, measuring gas evolution from a selected coal sample in two stages, bringing the carbon-gas sample into the state of sorption equilibrium after the first measurement stage, releasing gases into the atmosphere for a time equal to the interval between the rejection of the coal sample from array and the beginning of the measurement of gas evolution from it, re-measurement of gas evolution over a time equal to the time of the first measurement of gas evolution, determining the gas content of the formation by rmule consisting raw measurement data [4].

The disadvantages of the method are the multi-stage measurements of gas evolution, the need to bring the sample into a state of sorption equilibrium, adherence to the timing of the measurement of gas evolution and determination of gas content in sorption equilibrium and the residual gas content in the beaten coal, which does not contribute to the accuracy of determining the gas content of the formation.

The closest in technical essence is a method for determining the methane content of a coal seam, including the formation of a cavity in the plane of the coal seam, removal of beaten coal from the cavity, measuring methane consumption, determining the content of volatile substances, microcomponents of fusinite and vitrinite in a selected angle, establishing the dependence of the intensity of the reciprocal of the specific methane release from the cavity in time and methane content of the reservoir, taking into account the coefficient of proportionality in the identified dependence and the initial specific methane release [5].

The disadvantage of this method is that it is not necessary to determine the content of volatile substances, microcomponents of fusinite and vitrinite in the selected coal, the numerical values of which do not undergo significant changes within the coal seam and mine field. Moreover, the method does not allow to determine the methane content of the coal mass in the area of coal extraction by the combine.

The aim of the invention is to establish the methane content of the coal seam in the area of coal mining by the combine, that is, the methane content in the strip strip, which determines the intensity of methane release from the developed layer during the operation of the combine.

This goal is achieved by the fact that in the method for determining the methane content of a coal seam, including the conduct of degassing wells in the plane of the coal seam at the treatment site, measuring the flow of methane-air mixture from the wells and the methane content in it, determining the parameters of the formation gas return to the wells and the volume of methane extracted from during degassing, in addition to a non-working shift, the air flow rate and the methane content in it are measured at the exit from the lava, the length of the zone unloaded from the pressure of the coal mass in front of the face and the methane reserves in it, determine the degree of formation degassing by the wells and the natural degassing of the unloaded coal mass, after which, taking into account the total degree of formation degassing and its natural methane content, the methane content of the coal mass in the coal extraction zone is determined by the shearer, also set the degree of degassing of the formation by wells in terms of the volume of methane recovered and its reserves in the section of the reservoir that is degassed by the wells and the degree of natural degassing of the discharge coal mass ahead of the face - according to the measured methane consumption in the air stream at the exit from the lava, the duration of the mining of the formation zone subject to natural degassing, and the methane reserves in it, and the volumes of methane extraction from the formation in the preliminary degassing section are determined using the gas recovery indicators in degassing wells.

The method is as follows.

On the mine field section in the plane of the coal seam being developed, degassing wells are conducted, the methane-air mixture consumption and methane content are periodically measured from them, which are used to determine the methane consumption from drilled wells. After processing the obtained data, the dependence of the reciprocal of the intensity of specific methane release 1 / g on the time t of the functioning of the wells is established

where k is a coefficient (m ² / m ³ ) characterizes the gas-dynamic and filtration properties of a coal seam during its degassing by wells;

, обратная величина которого характеризует величину интенсивности начального удельного метановыделения из угольного пласта в дегазационные скважины;b - coefficient

the reciprocal of which characterizes the intensity of the initial specific methane release from the coal seam into degassing wells;

;g is the specific methane release rate in the wells

;

t is the duration of well operation, days.

The product of the numerical values of the coefficient k and g ₀ determines the rate a (day ^-1 ) of methane release from degassing wells from the time of their operation

(м³/м²) извлеченного метана из пласта через скважины за время дегазации t (сутки)where the values of g ₀ and a , which are indicators of the gas recovery of the coal seam in degassing wells, are used to determine the specific volume

(m ³ / m ² ) of extracted methane from the formation through the wells during the degassing time t (day)

where ln is the notation of the natural logarithm.

The amount of methane extracted from the formation G _c (m ³ ) over time t (day) is determined by the formula

where l _c is the effective length of the well, m;

m is the thickness of the degassed formation, m;

N is the number of drilled in the area of reservoir wells, pcs.

The degree to _c (fractions of units) of preliminary degassing of a coal seam by wells operating for a time t is determined by the formula

where W is the methane reserves in the degassed section of the reservoir, m ³ ; establish the product of coal reserves (Z, t) on the degassed area and methane content of the formation (X, m ³ / t SBM), determined during geological exploration or in another way.

The degree of _e (fraction of units) of natural degassing of the coal mass in front of the face due to the unloading effect of rock pressure is established by determining the length of the zone _{l.s. p} (m) of unloading the formation, the duration _t.s.p (days) of mining this zone, measuring during a non-working (repair) change of the air flow rate at the exit from the lava and the methane content in it, that is, the degree of natural degassing of the coal mass ahead of the face is determined by the formula

where G _z.r is the amount of methane released from the coal mass discharged by the bottom, m ³ ;

W _z.r - methane reserves within the discharge zone, m ³ .

I - the intensity of methane release from the coal seam exposed by the face of the coal seam (according to the measurement of air flow and methane content in it at the exit from the lava to an idle shift), m ³ / min;

t _{s_r} - the duration of the development of the reservoir within the unloading zone from rock pressure, days.

where l _z.r - the length of the discharge zone, m;

V _Pts - the speed of movement of the face, m / day.

Methane reserves within the unloading zone of the formation are determined by the formula

The length of the zone of unloading the formation by the face is determined by the readings of the hydraulic sensor, or by the dynamics of methane release from the formation well drilled parallel to the line of the face.

To determine methane intensity I (m ³ / min) were measured 3-4 times the air flow Q _into (m ³ / min) at the output of lava and content c (%) of methane in it a non-working shift (without any work on Coal breaking of the harvester)

where Q _in - air flow, m ³ / min;

c - methane concentration,%.

The total degree to _d.spl (fraction of units) of formation degassing due to preliminary (downhole) and natural (unloading of the massif from rock pressure) is determined by the formula

where k _with - the degree of degassing of the formation by wells, shares units;

to _e - the degree of natural degassing of the coal mass, fractions of units.

The methane content of X _in (m ³ / t SBM) of the formation in the zone of coal extraction by a shearer is determined by the dependence

where X is the natural methane content of the coal seam, m ³ / t SBM

Information sources

1. Instructions for determining and forecasting the gas content of coal seams and host rocks during exploration. M .: Nedra, 1977 .-- 96 p.

2. Ibid., P. 96.

3. Copyright certificate of the USSR No. 836365, M.Kl. ³ , E21F 7/00, E21F 5/00, Bull. No. 21, 1981

4. RF patent No. 2015348, C1, 5E21F 7/00, Bull. No. 12, 1994

5. RF patent No. 2372484, C1, IPC E21F 5/00, Bull. No. 31, 2009 (prototype).

Claims (4)

1. A method for determining the methane content of a coal seam, including conducting degassing wells in the plane of the coal seam at the treatment site, measuring the flow rate of the methane-air mixture from the wells and the methane content in it, determining the gas flow rate of the formation into the wells and the volume of methane recovered from it during degassing, characterized in that, in addition to a non-working shift, the air flow rate and methane content in it are measured at the exit from the lava, the length of the zone unloaded from the mountain pressure is established I of the coal mass ahead of the face and methane reserves in it, determine the degree of formation degassing by the wells and the natural degassing of the unloaded coal mass, after which, taking into account the total degree of formation degassing and its natural methane content, the methane content of the coal mass in the coal extraction zone is determined by the shearer. 2. The method according to claim 1, characterized in that the degree of formation degassing by the wells is determined by the volumes of methane recovered and its reserves in the formation section degassed by the wells. 3. The method according to claim 1, characterized in that the degree of natural degassing of the unloaded coal mass ahead of the face is determined by the measured methane flow rate in the air stream at the lava outlet, the duration of the mining zone exposed to natural degassing, and methane reserves in it. 4. The method according to claim 2, characterized in that the volumes of methane extraction from the formation in the preliminary degassing section are determined using the gas recovery parameters of the formation in degassing wells.