RU2166072C2 - Method of forming methane technogenic reservoir in coal seam - Google Patents

Abstract

FIELD: mining industry; applicable in reproduction of worked out gas reservoirs with subsequent recovery of methane from coal seams. SUBSTANCE: method includes hole drilling, supply to coal seam of methane-producing bacteria leaving to stand for formation of methane and withdrawal of methane. Bacteria are supplied after ceasing of methane recovery under conditions of self-emission to worked part of coal seam by injection of working fluid under conditions of hydraulic disjoint and leaving for some time of working fluid in seam with its subsequent displacement from filtering pores and fractures by injection of carbon dioxide gas and methane withdrawal. Said part of seam is separated from other rock mass by screen. Supplied successively are oxygen-removing and hydrogen-producing bacteria and let stand with no admission of oxygen to form commercial concentration of methane. In so doing, hydrogen-producing bacteria are supplied after 90% absorption of free oxygen in coal seam. Clostridium species are used as hydrogen-producing bacteria. EFFECT: higher efficiency of methane production from coal seam due to microbiological reproduction of methane. 3 cl, 1 dwg

Description

 The invention relates to the mining industry and can be used for the reproduction of exhaust gas deposits with the subsequent production of methane from a coal seam.

 A known method of degassing a coal seam, including opening a coal deposit and cyclic exposure to it with a liquid and a refrigerant (USSR copyright certificate N 1375839, 1988).

 There is also known a method of degassing a coal seam, including drilling wells, injecting fluid into the coal seam in the mode of hydraulic separation, supplying and holding fluid in the seam and its displacement from cracks and pores by supplying air or inert gas (USSR copyright certificate N 1511435, 1989).

 The closest analogue is a method for creating a technogenic methane deposit in the soil, bedrock, or in a coal seam, including drilling wells, injecting water through them into the reservoir containing bacteria and substances that ensure their vital activity, exposure to methane formation and methane extraction (PCT application N 79/00201, E 21 B 43/22, 04/19/1979).

 The disadvantage of these known methods is the low efficiency in the reproduction of methane over time.

 The objective of the invention is to increase the efficiency of methane production from a coal seam due to its microbiological reproduction.

 The problem is solved in that in the method of creating a man-made methane deposit in a coal seam, which includes drilling wells, feeding bacteria forming methane into the coal seam, holding until methane is formed and extracting methane, the bacteria are fed after methane extraction is stopped in self-discharge mode and into the developed a section of a coal seam obtained by injection of a working fluid in the mode of hydraulic separation with holding it in the seam followed by displacement from the filter pores and cracks by injection of carbon dioxide about gas and methane extraction, separated by a screen from the rest of the array, and oxygen-oxidizing and hydrogen-forming bacteria are subsequently fed and the exposure is carried out without oxygen until industrial methane concentrations are formed. Moreover, hydrogen-forming bacteria are fed after 90% oxidation of free oxygen in the coal seam, and bacteria of the genus Clostridium are used as hydrogen-forming.

 The drawing shows a variant of the scheme for creating a man-made methane deposit after its development from a coal seam according to the proposed method.

 The scheme includes a coal seam 1, well 2, plugged annular space 3, perforation of the well 4, bottom hole 5, fracture 6, screen 7.

 The method is as follows.

 Initially, the methane-containing coal seam 1 is opened by the borehole 2. Then the annulus 3 is successively plugged, the casing string 4 is perforated (not shown in the drawing) and a bottom hole 5 is formed by water supply. Then carry out the hydraulic separation of the reservoir 1 by the hydraulic effect of water injected under a pressure of 10-12 MPa. As the formation of cracks 6 initiate methane contained in the coal seam.

 To do this, carbon dioxide is fed into the formation 1 through the well 2, which replaces methane in coal and is not subsequently recovered to the surface. After completion of all initiation cycles, methane is removed, which gradually exits through the well 2 to the day surface. After 5-10 years of degassing of coal seam 1, the main amount of methane is extracted to the surface and the flow rate of well 2 for methane decreases sharply.

 After that, the worked out section of the coal seam 1 is shielded from the unprocessed array by screens 7, and then microorganisms oxidizing free oxygen are fed into it sequentially (together with products providing vital functions), and after its oxidation, hydrogen-forming bacteria.

In this case, it is necessary to take into account the methane renewal process known in natural systems, but not yet used in engineering and technology. Thus, microbiological studies have shown that bacterial methane reduction occurs solely due to the reduction of carbon dioxide by hydrogen. The conditions of many mines (temperature 15-20 ^o and pH 6.4-7.5) contribute to the occurrence of such microbiochemical processes of the targeted formation of technogenic methane. And since the formation of methane takes place in an anaerobic environment, for the development of these processes it is necessary to lower the oxygen concentration in the coal seam.

Thus, the process of microbiochemical technogenic methane formation includes the following stages of development:
oxidation of free oxygen by special bacteria;
microbiological formation of hydrogen;
the formation of methane as a result of the reaction:
CO ₂ + 4H ₂ = CH ₄ + 2H ₂ O (1)
As a result of sorption of the synthesized gas, a technogenic methane deposit is formed in the coal seam. After proceed to its production through the well 2.

 An example of a specific implementation of the proposed method is the following.

 After opening the coal seam 1 with the well 2 and completing the plugging of the annulus 3, perforating the casing 4, the hydrodisintegration of the seam 1 is performed. The pressure of injection of the working fluid (water) into the seam 1, the volume and rate of injection are determined by the generally accepted method. Water injection is carried out by pumping units 4AN-700.

After injection of the calculated volume of the working fluid, the well 2 is closed for 2-3 months. Then, four KPU-16/250 compressors are connected to well 2, which pump carbon dioxide into reservoir 1 with a total rate of 64 m ³ / min, which ensures its injection at a pressure of 12 MPa. After pumping the calculated volume of carbon dioxide, the well is closed for 10-15 days, and then methane is extracted from the reservoir in the self-flow mode.

After 5-10 years of degassing of coal seam 1, the main amount of methane is extracted to the surface and the flow rate of well 2 decreases sharply. Then, the worked out section of the coal seam 1 is separated from the rest of the array by a screen 7 (for example, injection of cement mortar through wells — not shown in the drawing), after which, together with substances providing vital functions, microorganism solutions (from the aerobic class) that oxidize free oxygen are supplied. Then, well 2 is closed and maintained until 90% oxygen is oxidized. After that, solutions of microorganisms forming hydrogen are fed into reservoir 1 (the main producers of hydrogen are chemotrophic bacteria that carry out anaerobic decomposition by the type of fermentation of various organic substrates, for example, representatives of the genus Clostridium, see "The role of microorganisms in the gas cycle in nature. M .: Science , 1979, pp. 131-132 "or Rhodospirillaceae - see Zavarzin GA" Bacteria and the composition of the atmosphere. M: Nauka, 1984, pp. 71-72 "- or cyanobacteria, - ibid., P. 116, 118) and close the well again until it is formed according to formula (I) as a result of the interaction of hydrogen with coal acid gas, technogenic methane to industrial concentrations (for example, up to 10 - 15 m ³ / t).

 As a result, a technogenic methane deposit is formed in the coal seam 1. After that, recovery is started again through the well 2.

 The positive effect of the proposed technical solution is to increase the efficiency of methane production from a coal seam due to its microbiological reproduction by the interaction of carbon dioxide with hydrogen.

 The present invention can be used in the industrial production of methane from a coal seam.

Claims (3)

 1. A method of creating a man-made methane deposit in a coal seam, which includes drilling wells, feeding bacteria forming methane into the coal seam, holding until methane is formed, and extracting methane, characterized in that the bacteria are fed after methane extraction is stopped in self-discharge mode and into the developed section coal seam obtained by injecting the working fluid in the mode of hydraulic separation with holding it in the seam, followed by displacement from the filter pores and cracks by injection of carbon dioxide, and extracted methane, separated by a screen from the rest of the array, and oxygen-oxidizing and hydrogen-forming bacteria are subsequently supplied and exposure is carried out without oxygen until industrial methane concentrations are formed.  2. The method according to claim 1, characterized in that the hydrogen-forming bacteria are fed after 90% oxidation of free oxygen in the coal seam.  3. The method according to claim 1 or 2, characterized in that bacteria of the genus Clostridium are used as hydrogen-forming.