RU2256079C1 - Method for extracting methane from coal bed - Google Patents

Abstract

FIELD: mining industry.

SUBSTANCE: method includes drilling directed wells from surface, extracting free methane, forcing substance into bed with absorption capacity greater than those of methane, with following extraction of methane from it. Closed circulation system is previously formed, formed by forcing and extracting wells for directed drilling with horizontal shafts perforated along whole length, filtering channels, formed by directional radial hydraulic fracturing of bed. Horizontal shaft of forcing well is positioned above horizontal shaft of extracting well. Then broad fraction of light hydrocarbons is fed into coal bed, extraction of which with absorbed methane is realized via extraction bed. Then along surface pipeline of extraction well substance is fed, saturated with methane, to separation station for separation of methane from broad fraction of light hydrocarbons. After separation gas is sent to consumer, and broad fraction of light hydrocarbons is sent through forcing well into coal bed. As absorbent, solar distillate or kerosene are used.

EFFECT: lower costs, simplified operation, higher personnel safety.

3 cl, 1 dwg

Description

The invention relates to geotechnological methods of mining, in particular to the extraction of methane from coal seams.

A known method for the extraction of coal methane from unloaded formations (RF patent No. 2211323, IPC E 21 B 43/26). The essence of the invention consists in drilling production wells, creating a coal methane production zone by initiating wells with the formation of cavities and hydraulic fractures by injecting fluid under pressure into the soil of the formation, connecting the initiating well, cavities and hydraulic fractures that make up the hydrodynamic system to pulsating hydrodynamic sources and vibration by injecting the working fluid in a pulsed mode into the corresponding hydrodynamic system. Production wells are drilled vertically beyond the contour of the coal methane production zone and open this zone with horizontal sections of production wells. The cavities are created in the initiating wells, and the formation of hydraulic fractures is carried out by injection in the fluid cavity under pressure at a distance of (0.5-1) m, where m is the thickness of the formation, respectively, above the roof and below the soil of the formation. Hydrodynamic systems are sealed independently of each other, and vibration exposure is carried out with the same magnitude, frequency and phase of vibration exposure in hydrodynamic systems. The disadvantage of this method is the low rate of gas recovery of the coal seam, limited by the throttle response of the horizontal wellbore.

A known method of extracting methane from a coal seam, adopted as a prototype (RF patent No. 2121062, IPC E 21 F 7/00). The method includes opening a formation by a borehole, casing it with pipes, grouting the annulus, perforating the casing and producing hydraulic separation with the formation of a system of cracks. Next, provide a mode of self-flow of methane from the reservoir and carry out its extraction. After the cessation of methane self-exhaustion, a substance with a sorption capacity, such as carbon dioxide, is pumped into a coal seam, in a volume determined from a mathematical expression that takes into account the length of the cracks uncovered during hydraulic decomposition, the thickness of the reservoir, the filtering porosity of the formation, the temperature of the injected substance, pressure the latter and the initial temperature of the formation, this substance is kept in the formation until the process of desorption of methane from coal ceases, after which methane is removed through one of the wells. The disadvantage of this method is the high cost of the reagents used and the difficulty of separating methane from carbon dioxide on the surface.

The technical result of the invention is to reduce the cost of reagents used through the use of waste oil refining and simplifying the separation of methane from the sorbent substance.

The technical result is achieved by the fact that in a method for extracting methane from a coal seam, including drilling directed wells from the surface, taking free methane, injecting into the formation a substance with a sorption capacity greater than that of methane, followed by extraction of methane from it, according to the invention, create a closed circulation system formed by injection and production wells of directional drilling with horizontal shafts perforated along the length, filtration channels formed by directional hydraulic fracturing, and the horizontal well of the injection well is located above the horizontal well of the production well, then a wide fraction of light hydrocarbons is pumped into the coal seam, which are sorbed with methane through the production well, then through the surface pipeline of the production well to the separation station to separate methane from the wide fractions of light hydrocarbons, which are directed through an injection well into a coal seam.

The method is also characterized by the fact that as a sorbent substance use a solar distillate or kerosene.

The application of the proposed method in comparison with the prototype will reduce the cost of the reagents used and simplify the separation of methane and sorbent substances.

The method of extracting methane from a coal seam is illustrated in the drawing, where

1 - coal seam;

2 - injection well;

3 - production well;

4 - filtration channels;

5 - land pipeline production wells;

6 - land pipeline injection wells;

7 - separation station;

8 - pumping station;

9 - pipeline for produced gas.

Most coals are natural sorbents. Gas in coal seams exists both in free and in bound states, which are in constant dynamic equilibrium with each other. At great depths, the bulk of the gas contained in coal is in a sorbed state. With the slow destruction of coal, even at high pressure, the gas remains trapped in the pores of the coal and its energy is spent on the process of slow filtration. Therefore, the gas-dynamic properties of the formation depend on the degree of disturbance. The laws and features of the manifestation of gas dynamics show that the mechanism of formation of a gas reservoir in a coal seam is possible in areas of geological disturbances by technogenic processes of formation of a discharge zone and the kinetics of methane desorption.

The method of extraction of methane from the coal seam 1 is as follows. The coal seam 1 is opened with directional drilling wells - injection 2 and production 3. Horizontal wells 2 and 3 are perforated along the length. Directed by radial hydraulic fracturing based on a wide fraction of light hydrocarbons, filter channels 4 are created and free gas is taken from the production well 3. Then, into the coal seam 1, using a pumping station 8, a substance with a sorption capacity greater than that of methane, a wide fraction of light liquid hydrocarbons, for example, solar distillate or kerosene, is fed through injection well 2 through an overland pipeline 6 of the injection well. Passing through natural cracks and pores of coal seam 1, and mainly through created filtration channels 4, a wide fraction of light hydrocarbons will adsorb methane from coal. When gas reservoirs are formed at depths up to 2000 m, the kinetics of methane desorption allows dissolving up to 1000 parts of methane in one part of a wide fraction of light hydrocarbons. The desorption properties are due to hydrophobization of the coal surface and contribute to the destruction of chemical bonds of carbon molecules with methane molecules. A substance saturated with methane is displaced through a production well 4, then, via a surface pipeline 5 of a production well, it is fed to a separation station 7, in which methane is separated from a wide fraction of light hydrocarbons. Then the gas is sent to the consumer via the pipeline 9 for the produced gas, a wide fraction of light hydrocarbons is fed into the coal seam 1 for saturation. With the development of methane reserves in the coal seam 1, wells located radially relative to the injection well are included in the operation. To reduce the cost of produced gas by reducing the volume of drilling additional wells, it is possible to use a beam of radially directed horizontal shafts from one vertical injection well. It is recommended to place the horizontal shafts of injection wells 2 below the horizontal shafts of production wells 3 to ensure the most effective filtration of rears and sorption of methane.

The use of this method for the extraction of methane from a coal seam provides the following advantages:

- reduction in the cost of reagents used due to the use of refinery waste;

- simplification of the separation of methane from the sorbent substance;

- increase the extraction of methane from the coal seam;

- reduction of anthropogenic pressure on the environment due to the creation of a closed circulation system.

Claims (3)

1. A method of extracting methane from a coal seam, including drilling directed wells from the surface, taking free methane, injecting into the formation a substance with a sorption capacity greater than that of methane, followed by extraction of methane from it, characterized in that they create a closed circulation system formed injection and production wells of directional drilling with horizontal shafts perforated along the length, filtration channels formed by directed radial hydraulic fracturing, and the horizon The injection wellbore is located above the horizontal wellbore of the production well, then a wide fraction of light hydrocarbons is pumped into the coal seam, which are sorbed with methane through the production well, then through the surface pipeline of the production well to the separation station to separate methane from the wide light hydrocarbon fraction sent through the injection well into the coal seam. 2. The method for extracting methane from a coal seam according to claim 1, characterized in that the solar distillate is pumped into the coal seam. 3. The method of extracting methane from a coal seam according to claim 1, characterized in that kerosene is pumped into the coal seam.