RU2278978C1 - Coal bed degassing method - Google Patents

Abstract

FIELD: mining, particularly to reduce gas content in gas-laden coal beds, especially in the case of low coal permeability.

SUBSTANCE: method involves drilling well; sucking gas to be drained through the well; intensifying gas discharge by loosening massif adjoining the well by gas-generation material introduction in the massif; impregnating the massif with liquid carbon dioxide to perform massif loosening; converting liquid carbon dioxide into gaseous state by supplying hot gas in well through sealing means, which prevents gaseous product leakage from well; repeatedly extracting gaseous products from well up to effluent gas discharge decrease; repeatedly loosening rock massif near well. Rock massif impregnation with liquid carbon dioxide is carried out under pressure, which corresponds to hydraulic fracturing of rock material. Propping agents, for instance fine material having hardness exceeding that of rock material, are added in liquid carbon dioxide. Fuel material combustion products may be used as the hot gas for liquid carbon dioxide gasification. Carbon dioxide is separated from gaseous product discharged from well.

EFFECT: possibility of method realization in any coal-mining region, increased ecological safety.

5 cl, 3 dwg

Description

The invention relates to the field of mining and can be used for the degassing of gas-rich coal seams, especially with low permeability of coal.

A known method of degassing a coal seam, including drilling the wells from the surface, injecting a working agent (water) into the reservoir in a steady state mode, followed by a sharp depressurization of the wellhead, with the formation of a formed pin and the formation of a slit-like cavity during repeated repetitions of the described process and suction of methane from this cavity (see the article by L. A. Puchkova et al. Coal methane - some problems and directions for their solution, Wl Coal, No. 12, 2003, p. 45).

The disadvantages of this solution are the high complexity of the process and waterlogging of the mineral, which significantly complicates subsequent work in conditions requiring low humidity of the mineral (for example, gasification of coal or oil shale) or requires subsequent drying of the extracted material.

There is also known a method of degassing a coal seam, including drilling a well, sucking drainage gas through it, carrying out work to intensify its flow rate by loosening the array adjacent to the well by introducing gas generating material into the array (see the article by L. A. Puchkov and other Coal Methane - Some problems and directions for their solution, Zh. “Coal”, No. 12, 2003, p. 45-46).

The disadvantage of this solution is the low processability of the method due to the need to use solutions of salts containing CO ₃ group (soda ash and potable soda, potash and calcium carbonate) and acid (phosphoric, hydrochloric, sulfuric) as gas generating material. Which limits the possibility of applying the method to regions where the named substances are not produced. In addition, the process is complicated by the aggressiveness of the components, requiring the use of special materials that are resistant to their effects and the use of special measures to eliminate damage to the environment.

The problem, the solution of which the claimed solution is directed, is expressed in increasing the manufacturability of the method.

The technical result obtained when solving the problem is expressed in that it provides the possibility of implementing the method in any coal mining region and ensures the environmental friendliness of the method in relation to the underground environment.

To solve this problem, a method of degassing a coal seam, including drilling a well, sucking drainage gas through it, carrying out work to intensify its flow rate, by loosening the array adjacent to the well by introducing gas-generating material into the array, differs in that, for loosening adjacent to the well the array is impregnated with liquid carbon dioxide, after which they initiate the transition of liquid carbon dioxide to a gaseous state, for which purpose into the well through a sealant that excludes the exit from of its gaseous products, gas is supplied at a temperature that ensures the transition of liquid carbon dioxide to a gaseous state, and upon completion of the loosening process, the process of suctioning gaseous products from the well is resumed and continued until the flow rate of the exhaust gas decreases, after which the loosening of the array adjacent to the well is repeated. In addition, the array is impregnated with liquid carbon dioxide with a pressure corresponding to the hydraulic fracturing pressure of the material composing it. At the same time, proppants, for example, finely dispersed material, the hardness of which is higher than the hardness of the material of the component, are introduced into liquid carbon dioxide, an array. In addition, gaseous products of the combustion of combustible materials are used as hot gases. At the same time, carbon dioxide is taken from the gaseous products extracted from the well.

A comparative analysis of the set of essential features of the claimed technical solution with the essential features of analogues and prototype indicates its compliance with the criterion of "novelty."

The features of the characterizing part of the claims solve the following functional tasks.

The sign "... for loosening the array adjacent to the well, it is impregnated with liquid carbon dioxide, after which they initiate the transition of liquid carbon dioxide to the gaseous state ..." excludes the possibility of water saturation of the mineral mass, in addition, the substance used is easily accessible, and its products "- gaseous carbon dioxide is easy to convert (restore) to combustible gas.

The signs "... into the well, through the sealant, which excludes the exit of gaseous products from it, gas is supplied at a temperature that ensures the transition of liquid carbon dioxide to the gaseous state ..." provide a pressure increase to a level exceeding the fracturing pressure of the material without the use of special equipment due to phase transition of carbon dioxide from liquid to gaseous state.

The signs "... at the end of the loosening process, the process of suctioning gaseous products from the well is resumed and continued until the flow rate of the exhaust gas decreases, after which loosening of the array adjacent to the well is repeated ..." ensure the continuous operation of the degassing well.

Moreover, the set of distinctive features of the second claim provides an increase in the efficiency of the loosening process.

The combination of features of the third paragraph of the claims increases the efficiency of the process of loosening, since it eliminates the "bonding" of the walls of the cracks after depressurization (before the introduction of hot gas).

The signs of the fourth claim of the invention increase the overall efficiency of the loosening process, since they allow you to utilize the gaseous products of combustion of combustible materials, including exhaust gases - products of the gasification process and gas obtained from the degassed array.

The characteristics of the fifth claim, provide continuous "reproduction" of carbon dioxide.

Figure 1 schematically shows a section through a degassed section during drainage of gas by in-situ pressure; In Fig.2 - the same, at the first stage of work on the intensification of gas production (injection of liquid carbon dioxide; Fig.3 - the same, at the stage of formation of the region of increased fracturing.

The drawings show a well 1, a vacuum pump 2, a coal seam 3, a source of gaseous CO ₂ , a source 5 of liquid CO ₃ , a feeder 6 of hydraulic fluid for hydraulic loosening, a heat generator 7, a sealant 8, a diverting well 9 of a gas generator, an area 10 of increased fracturing and gas permeability . In addition, the arrows show the movement of gaseous and liquid products during the implementation of the method.

The claimed method, it is advisable to use at underground gasification stations or in the presence of an underground gasification section, which allows you to select for the implementation of the method, carbon dioxide contained in the exhaust gases of underground gas generators (not shown), working at the station. The following example is provided specifically for such implementation conditions.

As the vacuum pump 2 use known devices of a similar purpose, corresponding in their performance characteristics to the parameters of the implemented method.

As a source of 5 liquid CO ₂ is used the installation of liquefying CO ₂ (of known construction) connected to a source 4 of gaseous CO ₂ (of known construction), as which may be used well-known apparatus for the separation of gaseous products of the gasification process providing separation from the rest of the CO ₂ off- gases taken from the outlet well 9 of the gas generator.

As a feeder 6 of fluid for hydraulic disintegration, hermetic mixers with thermostatically controlled cooled containers are used, which produce suspensions from a dispersed material that is buoyant in CO ₂ liquid (this can be wood flour or dispersed dry ice).

As a heat generator 7, for example, a gas turbine installation is used that burns the produced gas (gasification product) with the generation of steam or electricity.

The method is as follows.

A well 1 is drilled from the surface to the coal seam 3, which is connected to the vacuum pump 2. The vacuum pump is turned on and methane drained from the coal seam is sucked off. The selected gas (primary methane) is subjected to a known treatment (it is purified, compressed or liquefied and transferred to the consumer) or discharged into gas pipelines (not shown in the drawings), through which gases are removed from the gasification process, and then used in a known manner, for example, burned in a heat generator 7 (the drainage gas outlet channel is shown in dotted lines in FIG. 1).

After reducing the flow rate of well 1 to a predetermined level (determined by specific geological and mining conditions), work begins to intensify the flow rate of drainage gas - loosening the coal mass surrounding the well 1. To do this, disconnect the well from the corresponding pipeline receiving gas from the well, and connect the well to the fluid feeder 6 for hydraulic loosening.

Injection of a fluid for hydraulic fracturing (a suspension containing liquid carbon dioxide and a fine material insoluble in it, for example wood flour) is carried out into the well 1 under a pressure corresponding to the pressure of coal fracturing (in fact, up to 25-30 MPa) in the established mode. Then the well is closed with a sealant 8, which is used as a packer of known design, providing the ability to supply hot gas through it (flue gases of a heat generator 7), and supply the named gas.

As a result of heating to the phase transition temperature, liquid CO ₂ passes into a gaseous state, which leads to a sharp increase in pressure in the well and natural fractures of the array filled with liquid CO ₂ . This in turn leads to the destruction of the coal mass. This leads to the restoration of the flow rate of well 1.

At the first stage, after restoration of the flow rate of well 1, the gas mass begins to be discharged directly into the gas pipeline only after a corresponding drop in the content of gaseous CO ₂ in it. It is advisable at this stage to dump the gas mass into the source 4 of gaseous CO ₂ , which allows you to select carbon dioxide from the gas mass.

Thus, around the well 1, an area 10 of increased fracturing and gas permeability, unloaded from the rock pressure, is formed. Moreover, the named area develops in time and spreads deep into the massif, i.e. its self-sustaining destruction occurs.

The coal mass after loosening works is a structure containing a dense network of open cracks, which ensures effective gas degassing, and (with subsequent use of traditional development schemes and technologies) reduces the energy consumption of the coal extraction process.

The described effect, if necessary, is repeated many times, until the planned volume of methane is obtained, which reduces the gas content of the formation to parameters that ensure the subsequent effective operation of high-performance treatment equipment.

Claims (5)

1. A method of degassing a coal seam, including drilling a well, sucking out draining gas through it to carry out intensification of its flow rate by loosening the array adjacent to the well by introducing gas generating material into the array, characterized in that it is impregnated with liquid dioxide to loosen the array adjacent to the well carbon, after which they initiate the transition of liquid carbon dioxide to a gaseous state by supplying hot gas to the well with a temperature that ensures the transition of liquid carbon dioxide Erode in the gaseous state, and subsequent suction of gaseous products from the well. 2. The method according to claim 1, characterized in that the array is impregnated with liquid carbon dioxide with a pressure corresponding to the fracturing pressure of the material composing it. 3. The method according to claim 1, characterized in that proppants, for example finely dispersed material, the hardness of which is higher than the hardness of the material composing the array, are introduced into liquid carbon dioxide. 4. The method according to claim 1, characterized in that as the hot gases use gaseous products of the combustion of combustible materials. 5. The method according to claim 1, characterized in that carbon dioxide is taken from the gaseous products extracted from the well.

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