CN112901120B - Coal bed gas U-shaped well gas injection circulation negative pressure extraction device and method - Google Patents
Coal bed gas U-shaped well gas injection circulation negative pressure extraction device and method Download PDFInfo
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- CN112901120B CN112901120B CN202110337765.4A CN202110337765A CN112901120B CN 112901120 B CN112901120 B CN 112901120B CN 202110337765 A CN202110337765 A CN 202110337765A CN 112901120 B CN112901120 B CN 112901120B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/166—Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium
- E21B43/168—Injecting a gaseous medium
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/30—Specific pattern of wells, e.g. optimizing the spacing of wells
- E21B43/305—Specific pattern of wells, e.g. optimizing the spacing of wells comprising at least one inclined or horizontal well
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/34—Arrangements for separating materials produced by the well
Abstract
The invention discloses a coalbed methane U-shaped well gas injection circulation negative pressure extraction device and a method, wherein the system comprises a negative pressure extraction system, a gas injection pipe arranged in a horizontal well and a circulation gas supply system for communicating the negative pressure extraction system with the gas injection pipe; the circulating air supply system converts groundwater extracted from the negative pressure extraction system into high-temperature water vapor, and then the high-temperature water vapor is mixed with a small part of coal bed gas extracted from the negative pressure extraction system and is pressurized and then supplied into a coal reservoir through an air injection pipe; the method comprises the following steps: 1. constructing a U-shaped well and a coalbed methane U-shaped well gas injection circulation negative pressure extraction device; 2. depressurizing and pumping coal bed gas; 3. and negative pressure pumping coal bed gas. According to the invention, the mixed gas of the coal bed gas and the high-temperature vapor produced by the coal reservoir is injected into the coal reservoir, and the gas production efficiency is improved under the combined action of the ground negative pressure extraction, so that the method is convenient to popularize and use.
Description
Technical Field
The invention belongs to the technical field of coalbed methane exploitation, and particularly relates to a coalbed methane U-shaped well gas injection circulation negative pressure extraction device and method.
Background
Coal bed gas is an unconventional clean high-efficiency energy source, and at present, the coal bed gas in China has certain technical breakthrough and commercial development in different areas. However, compared with the countries such as the United states and Australia, the number of coal-bed gas wells in China is large, but the total gas production amount is low, and particularly the single-well gas production efficiency is low. The main reasons for the problems are that the existing ground coal bed methane development technology in China has low matching degree and poor adaptability with reservoir characteristics such as low pressure, low permeability and the like, and the gas production capability of the coal reservoir cannot be stimulated.
The exploitation mode of the ground coal bed gas in China mainly adopts a traditional operation system of drainage, depressurization and gas production, and CO is injected into a coal reservoir through fracturing fluid 2 、N 2 And chemically active agents or the like to enhance the reservoirPermeability and wettability, but injection of these fluids greatly destroys the original physical properties of the coal reservoir, severely affecting the recovery of coalbed methane. The on-site drainage of the ground coal-bed gas well discovers that once the drainage quantity is reduced, namely when the liquid level of a shaft is reduced below the coal bed, the drainage depressurization capacity of a screw pump is basically ineffective, and the gas production quantity is reduced, so that the problems severely restrict the development of the coal-bed gas industry in China.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the coal bed gas U-shaped well gas injection circulation negative pressure extraction device, which is used for improving the gas production efficiency by injecting the mixed gas of the coal bed gas produced by the coal reservoir and the high-temperature vapor into the coal reservoir and combining the ground negative pressure extraction, wherein the coal bed gas injected into the coal reservoir enhances the coal-water contact area by utilizing the coanda effect of fluid, and the high temperature and high pressure generated by the collapse of bubbles activate the desorption of the coal bed gas adsorbed in the coal bed; injecting high-temperature steam to increase the temperature of the coal reservoir through the heat carried by the steam, so as to enhance the desorption rate of the coal bed gas; the negative pressure extraction can excite the state of water in the coal matrix to change, combine water to change into free water and promote cavitation mass transfer, so that the desorption and migration of the adsorption gas of the coal reservoir are improved, the design is novel and reasonable, and the popularization and the use are convenient.
In order to solve the technical problems, the invention adopts the following technical scheme: the utility model provides a coalbed methane U type well gas injection circulation negative pressure extraction device, the U type well includes engineering well, production well and the horizontal well of intercommunication engineering well and production well, and the horizontal well is arranged in coal reservoir, its characterized in that: the system comprises a negative pressure extraction system arranged at the wellhead of a production well, an air injection pipe arranged in a horizontal well and a circulating air supply system used for communicating the negative pressure extraction system with the air injection pipe;
the circulating air supply system converts the groundwater extracted from the negative pressure extraction system into high-temperature vapor, and then the high-temperature vapor is mixed with a small part of coal bed gas extracted from the negative pressure extraction system and is pressurized, and then the mixture is supplied into a coal reservoir through an air injection pipe, so that gas adsorbed on the surface of coal in pores of the coal reservoir is desorbed.
Foretell a coalbed methane U type well gas injection circulation negative pressure extraction device, its characterized in that: the negative pressure extraction system comprises a water suction pump extending into the production well, a negative pressure pump arranged at the wellhead of the production well and a gas-water separator communicated with the negative pressure pump, a three-way pipe is arranged between the negative pressure pump and the wellhead of the production well, a first pipeline of the three-way pipe is communicated with the production well, a second pipeline of the three-way pipe is communicated with the air suction port of the negative pressure pump, a third pipeline of the three-way pipe is communicated with the gas-water separator,
the circulating air supply system comprises a water storage tank, a gas mixing tank, a first air supply pipeline for connecting the gas mixing tank and the water storage tank, and a second air supply pipeline for connecting an air outlet of the gas mixing tank and an air inlet pipe of the gas-water separator, wherein the gas mixing tank is communicated with the air inlet pipe through a mixed gas pipeline, a high-temperature steam generator and a first check valve arranged between the high-temperature steam generator and the gas mixing tank are arranged on the first air supply pipeline, a second check valve is arranged on the second air supply pipeline, a booster pump, a pressure gauge and a third check valve are sequentially arranged on the mixed gas pipeline, the booster pump is arranged close to the gas mixing tank, and a water outlet of the gas-water separator is connected with the water storage tank.
Foretell a coalbed methane U type well gas injection circulation negative pressure extraction device, its characterized in that: the exhaust port of the gas-water separator is divided into two paths, one path is communicated with the gas mixing box, and the other path is connected with the gas storage equipment.
Foretell a coalbed methane U type well gas injection circulation negative pressure extraction device, its characterized in that: the pipe section of the gas injection pipe extending into the horizontal well is provided with a plurality of gas injection ports.
Foretell a coalbed methane U type well gas injection circulation negative pressure extraction device, its characterized in that: the temperature of the steam output by the high-temperature steam generator is 80-100 ℃.
Foretell a coalbed methane U type well gas injection circulation negative pressure extraction device, its characterized in that: the volume ratio of the mixed gas in the gas mixing box is (90-95): (5-10) high-temperature steam and coalbed methane.
Foretell a coalbed methane U type well gas injection circulation negative pressure extraction device, its characterized in that: the gas pressure in the mixed gas pipeline after the booster pump is boosted is 1.3 Pc-1.7 Pc, wherein Pc is the bottom hole flow pressure of the horizontal well.
Foretell a coalbed methane U type well gas injection circulation negative pressure extraction device, its characterized in that: the water outlet end of the water suction pump is connected with the water storage tank.
Meanwhile, the invention also discloses a method for improving the extraction rate of the coal bed gas through the circulating negative pressure extraction of the coal bed gas, which has simple steps and reasonable design, and is characterized by comprising the following steps:
constructing a U-shaped well and a coalbed methane U-shaped well gas injection circulation negative pressure extraction device;
step two, depressurization and coal layer gas extraction:
step 201, turning on a water suction pump, pumping water into a water storage pool from a U-shaped well, reducing the liquid level in a production well, reducing the pressure of a coal storage pool, and starting gas production from the production well;
202, separating coal bed gas and water body from gas produced by a production well through a gas-water separator, wherein the separated water body enters a water storage tank, and the separated coal bed gas enters gas storage equipment;
step 203, after the flow of the coal bed gas separated in the gas-water separator is stable, opening a first one-way valve, a second one-way valve, a third one-way valve and a high-temperature steam generator, wherein the high-temperature steam generator extracts water in a water storage tank and outputs high-temperature steam to a gas mixing box, and one part of the coal bed gas separated by the gas-water separator enters the gas mixing box and the other part enters gas storage equipment;
the ratio of the gas in the gas mixing box is adjusted by adjusting the opening of the first one-way valve and the opening of the second one-way valve, and the volume ratio of the mixed gas in the gas mixing box is (90-95): (5-10) high-temperature steam and coalbed methane;
step 204, injecting mixed gas in the gas mixing box into a coal reservoir through a gas injection pipe after being pressurized by a booster pump, so that the gas adsorbed on the surface of coal in pores of the coal reservoir is desorbed, separating coal bed gas and water body from gas produced by a production well through a gas-water separator, wherein part of separated coal bed gas enters the gas mixing box and is pressurized again together with water vapor to be injected into the coal reservoir, and the other part of separated coal bed gas enters gas storage equipment to realize circulating extraction of the coal bed gas;
step three, extracting coal bed gas under negative pressure:
when the liquid level in the U-shaped well drops to the coal seam roof, the drainage pressure reduction capability of the water suction pump fails, the negative pressure pump is turned on at the moment, the pressure in the U-shaped well is reduced, the first one-way valve, the second one-way valve, the third one-way valve and the high-temperature steam generator are kept open, and the coal seam gas is continuously collected until the coal seam gas extraction operation is finished.
Compared with the prior art, the invention has the following advantages:
1. compared with nitrogen, the methane has better heat conduction performance, can collapse after the coal reservoir is attached to the wall, can instantaneously generate high temperature and vibration, stimulates the desorption of the coal bed gas and improves the yield.
2. According to the invention, the demand of the coalbed methane mixed with the high-temperature steam is small, and the desorption rate of the coalbed methane can be improved by mixing a small amount of methane gas with the high-temperature steam.
3. The invention fully utilizes and plays the role of the gas injection channel of the engineering well, and the injected gas is the mixed gas of the coalbed gas and the vapor of the coal reservoir, so that no pollution is generated to the coal reservoir in the extraction process of the coalbed gas, the cyclic extraction of the coalbed gas is realized, the problem that the water suction pump is easy to be buried by the pulverized coal is solved, and the extraction efficiency of the coalbed gas is greatly improved under the condition of protecting equipment.
4. The method has simple steps, is convenient for ground monitoring and is convenient to operate.
In summary, the design of the invention is novel and reasonable, the gas production efficiency is improved by injecting the mixed gas of the coalbed gas and the high-temperature vapor produced by the coal reservoir into the coal reservoir and combining the ground negative pressure extraction, wherein the coalbed gas injected into the coal reservoir enhances the coal-water contact area by utilizing the coanda effect of the fluid, and the high temperature and high pressure generated by the collapse of the bubbles activate the desorption of the coalbed gas adsorbed in the coal bed; injecting high-temperature steam to increase the temperature of the coal reservoir through the heat carried by the steam, so as to enhance the desorption rate of the coal bed gas; the negative pressure extraction can excite the state of water in the coal matrix to change, combine water to convert into free water, and promote cavitation mass transfer, thereby improving the desorption and migration of the adsorption gas of the coal reservoir and being convenient for popularization and use.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a schematic diagram of a coalbed methane U-shaped well gas injection circulation negative pressure extraction device.
Reference numerals illustrate:
1-an engineering well; 2-a production well; 3-a water suction pump;
4, a water storage pool; 5-a negative pressure pump; 6-a high temperature steam generator;
7-a gas-water separator; 8-a first one-way valve; 9-gas storage equipment;
10-a second one-way valve; 11-a gas mixing box; 12-a booster pump;
13-a pressure gauge; 14-a third one-way valve; 15-gas injection pipe;
16-gas injection port; 17-a three-way pipe; 18-a horizontal well;
19-a first air supply line; 20-a second air supply line; 21-a mixed gas pipeline.
Detailed Description
As shown in fig. 1, the coalbed methane U-shaped well gas injection circulation negative pressure extraction device of the present invention includes an engineering well 1, a production well 2, and a horizontal well 18 communicating the engineering well 1 and the production well 2, wherein the horizontal well 18 is located in a coal reservoir, and includes a negative pressure extraction system disposed at a wellhead of the production well 2, a gas injection pipe 15 disposed in the horizontal well 18, and a circulation gas supply system for communicating the negative pressure extraction system with the gas injection pipe 15;
the circulating air supply system converts the groundwater extracted from the negative pressure extraction system into high-temperature vapor, and then the high-temperature vapor is mixed with a small part of coal bed gas extracted from the negative pressure extraction system and is pressurized, and then the mixture is supplied into a coal reservoir through an air injection pipe 15, so that gas adsorbed on the surface of coal in pores of the coal reservoir is desorbed.
The invention adopts coal bed gas, namely methane is mixed with high temperature steam, compared with nitrogen, the methane has better heat conduction performance, can collapse after the coal reservoir is attached to the wall, can instantaneously generate high temperature and vibration, stimulates the desorption of the coal bed gas, and improves the yield.
The coal bed gas mixed with the high-temperature steam has smaller demand, and the desorption rate of the coal bed gas can be improved by mixing a small amount of methane gas with the high-temperature steam;
the mixed gas of the coal bed gas and the high-temperature vapor produced by the coal reservoir is injected into the coal reservoir, and the gas production efficiency is improved under the combined action of the ground negative pressure extraction, wherein the coal bed gas injected into the coal reservoir enhances the coal-water contact area by utilizing the coanda effect of the fluid, and the high temperature and the high pressure generated by the collapse of the bubbles activate the desorption of the coal bed gas adsorbed in the coal bed; injecting high-temperature steam to increase the temperature of the coal reservoir through the heat carried by the steam, so as to enhance the desorption rate of the coal bed gas; the negative pressure extraction can excite the state of water in the coal matrix to change, combine water to be converted into free water, and promote cavitation mass transfer, so that the desorption and migration of adsorbed gas of the coal reservoir are improved;
the invention fully utilizes and plays the role of the gas injection channel of the engineering well 1, and the injected gas is the mixed gas of the coalbed methane and the steam of the coal reservoir, so that no pollution is generated to the coal reservoir in the extraction process of the coalbed methane, the cyclic extraction of the coalbed methane is realized, meanwhile, the problem that the water suction pump 3 is easy to be buried by the pulverized coal is solved, and the extraction efficiency of the coalbed methane is greatly improved under the condition of protecting equipment;
compared with the prior art, the method does not need to additionally prepare and separate the gas with high heat conductivity, such as nitrogen, helium and the like, so that incomplete separation of the produced coal bed gas and other gases is avoided, the production process is simplified, and the production efficiency is improved.
In this embodiment, the negative pressure extraction system includes a water pump 3 extending into the production well 2, a negative pressure pump 5 disposed at the wellhead of the production well 2, and a gas-water separator 7 connected to the outlet of the negative pressure pump 5, a three-way pipe 17 is disposed between the negative pressure pump 5 and the wellhead of the production well 2, a first pipeline of the three-way pipe 17 is connected to the production well 2, a second pipeline of the three-way pipe 17 is connected to the extraction port of the negative pressure pump 5, a third pipeline of the three-way pipe 17 is connected to the gas-water separator 7,
the circulating air supply system comprises a water storage tank 4, an air mixing tank 11, a first air supply pipeline 19 for connecting the air mixing tank 11 and the water storage tank 4, and a second air supply pipeline 20 for connecting the air mixing tank 11 and an air outlet of the air-water separator 7, wherein the air mixing tank 11 is communicated with an air injection pipe 15 through a mixed air pipeline 21, a high-temperature steam generator 6 and a first one-way valve 8 arranged between the high-temperature steam generator 6 and the air mixing tank 11 are arranged on the first air supply pipeline 19, a second one-way valve 10 is arranged on the second air supply pipeline 20, a booster pump 12, a pressure gauge 13 and a third one-way valve 14 are sequentially arranged on the mixed air pipeline 21, the booster pump 12 is arranged close to the air mixing tank 11, and a water outlet of the air-water separator 7 is connected with the water storage tank 4.
In this embodiment, the water pump 3 is a screw pump.
After the coal bed gas mixed with the high-temperature vapor and injected into the coal reservoir acts on the coal reservoir, the coal bed gas enters the gas-water separator 7 through the production well 2 to be distributed again, so that no gas leakage exists in the whole process, no pollution is caused to the environment, the production safety is ensured, and the use effect is good.
In this embodiment, the exhaust port of the gas-water separator 7 is divided into two paths, one path is communicated with the gas mixing box 11, and the other path is connected with the gas storage device 9.
In this embodiment, the second check valve 10 on the second air supply pipeline 20 is used to control the amount of the coal seam gas passing through the two channels of the air outlet of the air-water separator 7, and the opening of the second check valve 10 is adjusted to make the amount of the coal seam gas output by the second air supply pipeline 20 reach the value when the mixed gas in the gas mixing box 11 needs more coal seam gas.
In this embodiment, the pipe section of the gas injection pipe 15 extending into the horizontal well 18 is provided with a plurality of gas injection ports 16.
In this embodiment, the plurality of gas injection ports 16 are uniformly arranged along the length direction of the horizontal well 18, and a section of the gas injection pipe 15 is circumferentially provided with the plurality of gas injection ports 16.
In this embodiment, the gas injection pipe 15 is a high temperature resistant stainless steel pipe, and the end of the gas injection pipe 15 close to the production well 2 is not closed, so that the injected coalbed methane in the coal reservoir is allowed to agitate the water body in the horizontal well 18, the contact area of coal and water is increased, the micro-impact of the injected gas can prevent the coal dust from burying the pump at the bottom of the production well 2, and the possibility of interruption of drainage is reduced.
In this embodiment, the temperature of the steam output from the high-temperature steam generator 6 is 80 ℃ to 100 ℃.
The temperature of the mixed gas injected into the coal reservoir is controlled within 80-100 ℃ through water vapor, the water vapor generates heat transfer effect and wetting effect on the coal reservoir, the water vapor directly transfers carried heat to the coal reservoir, the top surface of the horizontal shaft is separated from the water surface along with the progress of drainage and depressurization, and the wetting effect on the surface of the reservoir is enhanced by the injection of the water vapor. The injected water vapor is not too high or too low in temperature, and the water vapor with too high temperature, such as 230 ℃, can cause clay mineral expansion in the coal bed, so that a gas production channel of the coal bed gas is easily blocked, and the heat transfer effect is poor and the yield of the coal bed gas is not high.
In this embodiment, the mixed gas in the gas mixing tank 11 is composed of (90 to 95) by volume ratio: (5-10) high-temperature steam and coalbed methane.
The solubility of coal bed gas, i.e. methane, was 3.5mg/100ml, i.e. 3.38%, at 17 ℃. Because the temperature of the injected gas is between 80 ℃ and 100 ℃, the solubility of the gas is increased, the volume of the injected methane gas is set to be 5% -10% in order to prevent the mixed methane gas from being completely dissolved, and under the concentration, the mixed gas is injected into a coal reservoir, methane gas molecules collapse after the wall of the coal reservoir is attached, high temperature and vibration are instantaneously generated, and the desorption of the coal bed gas is stimulated.
It should be noted that, after mixing and pressurizing, a small part of the coalbed methane extracted in the negative pressure extraction system is supplied into the coal reservoir through the gas injection pipe 15, and the volume of the small part of the coalbed methane is the volume of the coalbed methane required in the gas mixing box 11.
In this embodiment, the gas pressure in the mixed gas pipeline 21 after the pressurization of the booster pump 12 is 1.3Pc to 1.7Pc, where Pc is the bottom hole flow pressure of the horizontal well 18.
It should be noted that, too high a gas injection pressure easily causes the injected methane gas to be pressed into the coal reservoir, so that the effects of displacement and gas production excitation are not achieved, and too low a gas injection pressure is insufficient to generate water-gas agitation.
In this embodiment, the negative pressure extraction pressure is set to be 0.05Mpa, and desorption and migration of the coalbed methane can be continuously promoted in the later stage, because the minimum exhaustion pressure of the coalbed methane well is 0.2Mpa and the normal atmospheric pressure is 0.1Mpa at present.
In this embodiment, the water outlet end of the water pump 3 is connected to the water storage tank 4.
The underground water pumped by the water pump 3 provides a water source for the water storage tank 4, and meanwhile, high-temperature steam which is introduced into the coal reservoir is also from the coal reservoir, so that pollution to the coal reservoir is avoided.
A method as shown in fig. 1, comprising the steps of:
constructing a U-shaped well and a coalbed methane U-shaped well gas injection circulation negative pressure extraction device;
in the embodiment, according to the construction requirements and the sequential construction of the U-shaped coal bed methane well, the engineering well 1 and the production well 2 of the U-shaped well and the horizontal well 18 which are communicated with the engineering well 1 and the production well 2 are constructed, the horizontal well 18 is positioned in a coal reservoir, the engineering well 1 and the production well 2 are vertical shafts, and the conventional well cementation operation is carried out on the engineering well 1 and the production well 2;
step two, depressurization and coal layer gas extraction:
step 201, turning on a water suction pump 3, pumping water from a U-shaped well into a water storage tank 4 by the water suction pump 3, reducing the liquid level in a production well 2, reducing the pressure of coal storage layer, and starting to produce gas by the production well 2;
202, separating coal bed gas and water body from gas produced by a production well 2 through a gas-water separator 7, wherein the separated water body enters a water storage tank 4, and the separated coal bed gas enters a gas storage device 9;
step 203, after the flow rate of the coal bed gas separated in the gas-water separator 7 is stable, opening a first one-way valve 8, a second one-way valve 10, a third one-way valve 14 and a high-temperature steam generator 6, wherein the high-temperature steam generator 6 extracts water in the water storage tank 4 and outputs high-temperature steam to the gas mixing tank 11, one part of the coal bed gas separated by the gas-water separator 7 enters the gas mixing tank 11, and the other part enters the gas storage device 9;
the ratio of the gas in the gas mixing tank 11 is adjusted by adjusting the opening of the first check valve 8 and the second check valve 10, and the volume ratio of the mixed gas in the gas mixing tank 11 is (90-95): (5-10) high-temperature steam and coalbed methane;
step 204, the mixed gas in the gas mixing box 11 is pressurized by the booster pump 12 and then injected into a coal reservoir through the gas injection pipe 15, so that the gas adsorbed on the surface of coal in the pores of the coal reservoir is desorbed, the gas produced by the production well 2 is separated into coalbed gas and water body through the gas-water separator 7 again, part of the separated coalbed gas enters the gas mixing box 11 and is pressurized again together with the high-temperature steam to be injected into the coal reservoir, and the other part of the separated coalbed gas enters the gas storage equipment 9, so that the circulating extraction of the coalbed gas is realized;
step three, extracting coal bed gas under negative pressure:
when the liquid level in the U-shaped well drops to the coal seam roof, the drainage pressure reduction capability of the water suction pump 3 fails, the negative pressure pump 5 is turned on at the moment, the pressure in the U-shaped well is reduced, the first one-way valve 8, the second one-way valve 10, the third one-way valve 14 and the high-temperature steam generator 6 are kept on, and the coal seam gas is continuously collected until the coal seam gas extraction operation is finished.
Note that, the present invention is not limited to the above-described embodiments. When the high-temperature steam generator 6 is started, the current water amount in the water storage tank 4 needs to be ensured to reach the lower limit of the water storage amount;
after the coal bed gas mixed with the high-temperature vapor and injected into the coal reservoir acts on the coal reservoir, the coal bed gas enters the gas-water separator 7 through the production well 2 to be distributed again, so that no gas leakage exists in the whole process, no pollution is caused to the environment, the production safety is ensured, and the use effect is good.
In the embodiment, the negative pressure extraction pressure is set to be 0.05Mpa, so that desorption and migration of coal bed methane can be continuously promoted in the later stage.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modification, variation and equivalent structural changes made to the above embodiment according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.
Claims (3)
1. The utility model provides a coalbed methane U type well gas injection circulation negative pressure extraction method, the U type well includes engineering well (1), production well (2) and horizontal well (18) of intercommunication engineering well (1) and production well (2), and horizontal well (18) are located coal reservoir, its characterized in that: the device comprises a negative pressure extraction system arranged at the wellhead of a production well (2), an air injection pipe (15) arranged in a horizontal well (18) and a circulating air supply system used for communicating the negative pressure extraction system with the air injection pipe (15);
the circulating air supply system converts groundwater extracted from the negative pressure extraction system into high-temperature vapor, and then the high-temperature vapor is mixed with a small part of coal bed gas extracted from the negative pressure extraction system and is supplied into a coal reservoir through an air injection pipe (15) after being pressurized, so that gas adsorbed on the surface of coal in pores of the coal reservoir is desorbed;
the negative pressure extraction system comprises a water suction pump (3) extending into the production well (2), a negative pressure pump (5) arranged at the wellhead of the production well (2) and a gas-water separator (7) communicated with the outlet of the negative pressure pump (5), a three-way pipe (17) is arranged between the negative pressure pump (5) and the wellhead of the production well (2), a first pipeline of the three-way pipe (17) is communicated with the production well (2), a second pipeline of the three-way pipe (17) is communicated with the extraction opening of the negative pressure pump (5), and a third pipeline of the three-way pipe (17) is communicated with the gas-water separator (7);
the circulating air supply system comprises a water storage tank (4), an air mixing tank (11), a first air supply pipeline (19) for connecting the air mixing tank (11) with the water storage tank (4), and a second air supply pipeline (20) for connecting the air mixing tank (11) with an air outlet of the air-water separator (7), wherein the air mixing tank (11) is communicated with an air injection pipe (15) through a mixed air pipeline (21), a high-temperature steam generator (6) and a first one-way valve (8) arranged between the high-temperature steam generator (6) and the air mixing tank (11) are arranged on the first air supply pipeline (19), a second one-way valve (10) is arranged on the second air supply pipeline (20), a booster pump (12), a pressure gauge (13) and a third one-way valve (14) are sequentially arranged on the mixed air pipeline (21), the booster pump (12) is arranged close to the air mixing tank (11), and a water outlet of the air-water separator (7) is connected with the water storage tank (4);
the temperature of the steam output by the high-temperature steam generator (6) is 80-100 ℃;
the water outlet end of the water suction pump (3) is connected with the water storage tank (4);
the method comprises the following steps:
constructing a U-shaped well and a coalbed methane U-shaped well gas injection circulation negative pressure extraction device;
step two, depressurization and coal layer gas extraction:
step 201, opening a water suction pump (3), pumping water into a water storage pool (4) from a U-shaped well by the water suction pump (3), reducing the liquid level in a production well (2), reducing the pressure of a coal storage pool, and starting to produce gas by the production well (2);
202, separating coal bed gas and water body from gas produced by a production well (2) through a gas-water separator (7), wherein the separated water body enters a water storage tank (4), and the separated coal bed gas enters a gas storage device (9);
step 203, after the flow rate of the coal bed gas separated in the gas-water separator (7) is stable, a first one-way valve (8), a second one-way valve (10), a third one-way valve (14) and a high-temperature steam generator (6) are opened, the high-temperature steam generator (6) extracts water of the water storage tank (4) and outputs high-temperature steam to the gas mixing box (11), one part of the coal bed gas separated by the gas-water separator (7) enters the gas mixing box (11), and the other part of the coal bed gas enters the gas storage equipment (9);
the gas ratio in the gas mixing box (11) is adjusted by adjusting the opening degree of the first check valve (8) and the second check valve (10);
step 204, the mixed gas in the gas mixing box (11) is pressurized by the booster pump (12) and then is injected into the coal reservoir through the gas injection pipe (15), so that the gas adsorbed on the surface of the coal in the pores of the coal reservoir is desorbed, the gas produced by the production well (2) is separated into coalbed methane and water body through the gas-water separator (7), part of the separated coalbed methane enters the gas mixing box (11) and is pressurized again together with the high-temperature steam to be injected into the coal reservoir, and the other part of the separated coalbed methane enters the gas storage equipment (9) to realize the circulating extraction of the coalbed methane;
step three, extracting coal bed gas under negative pressure:
when the liquid level in the U-shaped well drops to the coal seam roof, the drainage depressurization capacity of the water suction pump (3) fails, the negative pressure pump (5) is turned on at the moment, the pressure in the U-shaped well is reduced, the first one-way valve (8), the second one-way valve (10), the third one-way valve (14) and the high-temperature steam generator (6) are kept open, and the coal seam gas is continuously collected until the coal seam gas extraction operation is finished;
the volume ratio of the mixed gas in the gas mixing box (11) is (90-95): (5-10) high-temperature steam and coalbed methane;
the gas pressure in the mixed gas pipeline (21) after the pressurization of the booster pump (12) is 1.3 Pc-1.7 Pc, wherein Pc is the bottom hole flow pressure of the horizontal well (18);
the excessive gas injection pressure easily causes the injected methane gas to be pressed into the coal reservoir, so that the effects of displacement and gas production excitation are not achieved, and the too small gas injection pressure is insufficient to generate the water-gas agitation;
the coal bed gas injected into the coal reservoir enhances the coal-water contact area by utilizing the coanda effect of the fluid, and the high temperature and high pressure generated by the collapse of the bubbles activate the desorption of the coal bed gas adsorbed in the coal bed;
in order to prevent the mixed methane gas from being completely dissolved, the volume of the injected methane gas is set to be 5% -10%, and at the concentration, the mixed gas is injected into a coal reservoir, methane gas molecules collapse after the coal reservoir is attached to the wall, high temperature and vibration are instantaneously generated, and the desorption of the coal bed gas is stimulated.
2. The method for extracting the negative pressure of the gas injection circulation of the U-shaped well of the coal bed gas according to claim 1 is characterized in that: the exhaust port of the gas-water separator (7) is divided into two paths, one path is communicated with the gas mixing box (11), and the other path is connected with the gas storage device (9).
3. The method for extracting the negative pressure of the gas injection circulation of the U-shaped well of the coal bed gas according to claim 1 is characterized in that: the pipe section of the gas injection pipe (15) extending into the horizontal well (18) is provided with a plurality of gas injection ports (16).
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| CN100351491C (en) * | 2002-12-13 | 2007-11-28 | 石油大学(北京) | Thermal recovery method for coal seam gas |
| US7681639B2 (en) * | 2008-06-17 | 2010-03-23 | Innovative Drilling Technologies LLC | Process to increase the area of microbial stimulation in methane gas recovery in a multi seam coal bed/methane dewatering and depressurizing production system through the use of horizontal or multilateral wells |
| CN204436342U (en) * | 2015-02-02 | 2015-07-01 | 陕西龙门天地油气技术有限公司 | Coal bed gas negative pressure on ground drainage device |
| CN104790915B (en) * | 2015-04-22 | 2017-04-26 | 西南石油大学 | Coal bed methane recovery method |
| CA2920656C (en) * | 2016-02-11 | 2018-03-06 | 1304342 Alberta Ltd. | Method of extracting coal bed methane using carbon dioxide |
| CN107387045A (en) * | 2017-07-20 | 2017-11-24 | 苏州大学 | A kind of coal bed gas heating exploitation system and recovery method |
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