RU2024767C1 - Method for degassing coal seam - Google Patents

Abstract

FIELD: mining. SUBSTANCE: method for degassing coal seam includes drilling of degassing holes in worked mass from mine working, and releasing-degassing cracks-slots are made in holes. Degassing holes are drilled in places with high pressures P_п/P_п>pH,, where p is average specific densities of rocks above mass, H is depth of coal mass occurrence. Cracks-slots are made by shaking of coal mass from hole in vertical direction. EFFECT: higher efficiency.

Description

 The invention relates to mining, and more particularly to methods for degassing coal seams and extracting methane from the array, and can be used in underground mining of coal deposits to prevent gas-dynamic phenomena; sudden emissions of coal and gas, sudden emissions of gas and coal fines, gas breakthroughs, soufflings, as well as for the extraction of methane from the seams to increase the calorific value of the produced coal.

 A known method of stratified degassing of mines, including drilling degassing wells in a developed array from a mine, creating a system of unloading and degassing cracks-cracks in the wells, oriented cross-bed, equipment of the wells and suction of methane from the wells [1]. The disadvantage of this method is the low efficiency of reservoir degassing of the mine.

, где Х_р - расстояние границы разгружающе-дегазирующего влияния выработки от ее поверхности, м; Х - расстояние в глубь массива, соответствующее проницаемости пласта λ; λ_* - природная газопроницаемость пласта, мД; λ_о- газопроницаемость пласта на поверхности обнажения в выработке, мД; а последующие разгружающе-дегазирующие щели, ориентированные вкрест напластования, выполняют на расстояниях, равных двойному радиусу разгружающе-дегазирующего влияния трещин-щелей [2]. Недостатком известного способа является все еще низкая эффективность дегазации и невозможность извлечения метана из массива.There is a known method of degassing a coal seam, including drilling degassing wells along a developed array from production, creating a system of discharge-degassing cracks-cracks in the wells oriented crosswise to bedding, equipping the wells and extracting methane from the wells, in which, in order to increase the efficiency of degassing in the degassing wells, systems of cracks oriented parallel to the bedding, while all unloading-degassing cracks-cracks, oriented crosswise to the bedding, are generating parallel nyayut wall nearest the wellhead fracture gap-operate at the boundary razgruzhayusche-degassing effect generation at a distance from the production, determined from the expression
X _p =

, where X _p is the distance of the border of the discharge-degassing effect of the mine from its surface, m; X is the distance into the interior of the array corresponding to the permeability of the reservoir λ; λ _* - natural gas permeability of the formation, MD; λ _about - gas permeability of the formation on the surface of the outcrop in the development, MD; and subsequent unloading-degassing cracks, oriented across the bed, perform at distances equal to the double radius of the unloading-degassing effect of crack-cracks [2]. The disadvantage of this method is the still low degassing efficiency and the inability to extract methane from the array.

 The aim of the invention is to increase the efficiency of degassing and expanding the functionality of the method by ensuring the extraction of methane from the array by adsorption and chemisorption of methane into coal.

This is achieved by the fact that in the method of degassing a coal seam, including drilling degassing wells along a developed array from a mine and creating unloading-degassing cracks-gaps in the wells, the degassing wells are drilled at high pressures P _p / P _p > pH, where p is the average coal density of rocks over the massif (their specific gravity); H is the depth of the massif), and cracks-cracks form by shaking the massif from the wells in the vertical direction.

An inventive act in creating a method consists in overcoming a technical contradiction, the essence of which is as follows. In conventional engineering design (as opposed to invention), in order to expand the functionality, they usually resort to additional steps to give the method new advanced functionality. But this inevitably complicates the method. So, for example, for additional extraction of methane from the reservoir in the known method [3], the working fluid is injected into the well at a rate exceeding the natural injectivity of the array, and the working fluid is pumped out after methane accumulation in the filter element. In the present method, this technical contradiction has been overcome - increasing the degassing efficiency and expanding functionality by providing methane extraction from the array by adsorption and chemisorption of methane into coal are achieved while simplifying the method. To overcome this technical contradiction, the following distinctive features of the method are necessary and sufficient: ¹⁾ degassing wells are drilled in places of high pressures; ²⁾ shake the array of degassing wells in a vertical direction. The first distinguishing feature is known individually by itself, although it has never before served to overcome this technical contradiction. The second distinguishing feature is not even known individually, especially since it could never serve to overcome a technical contradiction. Both signs are formulated specifically in the sense of the uniqueness of the operations performed. At the same time, both features are formulated generally in the sense of their independence from options for the implementation of devices or materials for performing specific operations. Therefore, it is impossible to replace with an equivalent none of the two distinguishing features. If any of the distinguishing features is excluded, then the goal will not be achieved, which clearly follows from the description of the method below. Therefore, according to the author, the combination of two distinctive features meets the criteria of "Novelty" and "Significant differences", and the proposed method meets the inventive step.

The method of degassing a coal mass is carried out in the following sequence of operations. In places of high pressures P _p / where P _p > pH, p is the average specific gravity of the rocks above the coal mass; H is the depth of the array), degassing wells are drilled along the developed array. Cracks-cracks in the array are formed by shaking the array from the wells in the vertical direction. When the mass is shaken, cracks-cracks first increase with increasing pressure in the cracks, and then the cracks sharply decrease in size, and methane is adsorbed and chemisorption into the coal seam.

PRI me R. At the start of shaking (at the first stage), the fractures (pores) of the formation expand and methane throttles into expanding fractures of the formation. During throttling, the methane temperature increases according to the Joule-Thomson effect, since the methane inversion temperature is -40 ^о С and when methane expands (throttles) in the production face with a temperature of +20 ^о С, the Joule-Thomson coefficient is -0.28 К / 10 ⁵ Pa According to the effect
μ = ΔT / ΔP, (1) where ΔТ = Т ₂ - Т _{1 is} the temperature difference achieved during methane expansion; ΔP = P ₁ - P ₂ - pressure change during methane expansion; μ is the Joule-Thomson coefficient. If, for example, T ₁ = 293 K, P ₁ = 200 at = 200 ˙ 0.980665 ˙ 10 ⁵ Pa = 196.133 ^. 10 ⁵ Pa, and P ₂ = 50 at = 50 ˙ 0.980665 ˙ 10 ⁵ Pa = 49.03 ˙ 10 ⁵ Pa, then ΔP = 147.103 ˙ 10 ⁵ Pa. Then T ₂ = T ₁ + ΔP μ = 293K + 147.103 ^. 10 ⁵ Pa ˙ 0.28K / 10 ⁵ Pa = 334.2 K, that is, the temperature will increase by 41.2 ^about C.

=
= 13345,4K или 13072^°C
В процессе сжатия метана его температура повышается постепенно и сначала происходит в основном из-за сжатия адсорбции метана в угольный пласт. При давлении 200 ат (или 2 МПа) природным углем сорбируется уже около 17 см³/г метана. При этом молекулы метана будут удерживаться поверхностью угля необратимо, так как размеры молекулы метана и размеры микропор угля соизмеримы и имеют величину порядка 4А. При нагревании метана выше 450^оС (или выше 723 К) начинается хемосорбция метана в уголь с образованием химических соединений метана с углем. С ростом температуры абсорбции и адсорбции уменьшаются, а хемосорбция метана в уголь резко растет. Так как процесс повышения температуры метана при сжатии пласта в пределах упругих деформаций пласта происходит не мгновенно, то метан входит в уголь за счет абсорбции, адсорбции и хемосорбции раньше, чем он нагреется до температуры 800-1000^оС, причем процесс происходит необратимо. Замедлению нагрева метана способствует и расход части тепла на нагрев самого массива угля.After shaking the formation (in the second stage), the cracks narrow under the action of a pressure of 200 atm and in the second stage the methane is also heated above the temperature of 334.2 K. We calculate this heating for the case when the formation is working on the methane mole to compress methane pores from pressure 50 atm to a pressure of 200 atm, and when the work A = P ₁ (V ₂ - V ₁ ) goes to the increment of the internal energy of the same mole of methane U = C _v (T ₃ - T ₂ ), that is, when
P ₁ (V ₂ - V ₁ ) + C _V (T ₃ - T ₂ ) = 0, (2) or
C _V (T ₃ - T ₂ ) + RT ₃ = P ₁ V ₁ . (3) Therefore, from (3) we obtain
T ₃ = C _p ¹ (C _V T ₂ - P ₁ T ₁ ). (4) In formula (4) it is indicated: С _p is the specific heat of methane at constant pressure, numerically equal to the product of the specific heat of methane per 1 kg of its weight in 2089.05 J kg ^-1 K ^-1 by the weight of 1 mole of methane 22.4 dm ³ ˙ 0.717 kg / m ³ = 0.01606 kg, that is, numerically equal to C _p = 2089.05 x x 0.0160608 = 33.552 J / K; C _V is the specific heat of methane at a constant volume, numerically equal to the product of the specific heat of methane per 1 kg of its weight in 1570.05 J kg ^-1 K-1 by the weight of one mole of methane 0.0160608 kg, that is, numerically equal to the value of C _V = 1570.05 ^. 0.0160608 = 25.216 J / K; V ₁ is the volume of one mole of methane, V ₁ = 0.0224 m ³ . According to formula (4) we get
T ₃ =

=
= 13345.4K or 13072 ^° C
In the process of methane compression, its temperature rises gradually and at first occurs mainly due to compression of methane adsorption into the coal seam. At a pressure of 200 bar (or 2 MPa), about 17 cm ³ / g of methane is already adsorbed by natural coal. In this case, methane molecules will be held irreversibly by the surface of the coal, since the dimensions of the methane molecule and the sizes of the coal micropores are comparable and have a value of the order of 4A. When methane is heated above 450 ^° C (or above 723 K), methane chemisorption into coal begins with the formation of chemical compounds of methane with coal. With increasing temperature, the absorption and adsorption decrease, and the chemisorption of methane into coal increases sharply. Since the process of raising the temperature of the methane formation compressive strain within the elastic layer is not instantaneous, the methane enters the coal by absorption, adsorption and chemisorption before it warms up to a temperature of 800-1000 ^{° C,} wherein the process is irreversible. The methane consumption is also slowed by the consumption of part of the heat for heating the coal mass itself.

 Thus, after several shaking of the formation, practically all methane in the coal pores enters the coal seam. The process is irreversible and therefore the goal is achieved, that is, at the same time the degassing efficiency is increased and methane is extracted into the coal seam, which increases its calorific value. Both processes occur during the absorption, adsorption and chemisorption of methane into the coal seam.

 The advantages of the proposed method in comparison with the prototype are: the method is simplified by eliminating the process of suction of methane from the wells, the process of performing additional cracks cross-bedding is excluded, the functionality is expanded by ensuring the utilization of methane directly into the coal seam. To obtain these advantages, all the restrictive and distinctive features of the method are necessary and sufficient.

Claims (1)

METHOD OF COAL LAYER DEGASING, including drilling of degassing wells along the developed array from production and creating unloading-degassing cracks-cracks in the wells, characterized in that the degassing wells are drilled in places of high pressures P _p (P _p > pH, where p is the average specific density rocks above the massif; H is the depth of the massif), and crack-cracks form by shaking the massif from the well in the vertical direction.