Carbon dioxide fracturing, displacement and gas extraction integrated device and application method thereof

Abstract

The invention relates to the field of coal seam gas extraction, in particular to a carbon dioxide fracturing, displacement and gas extraction integrated device and an application method thereof. The device comprises a controller, a fracturing and extraction device body, a gas source tank, a gas booster pump and a gas collecting tank. The fracturing and extraction device body comprises an inner pipe and an outer pipe, the inner pipe is a fracturing pipe, the outer pipe is an extraction pipe, the outer pipe surrounds the circumference of the outer side of the inner pipe, and a carbon dioxide fracturing device is installed at the front end of the inner pipe. And the inner pipe and the outer pipe are respectively connected with a gas source tank and a gas collecting tank through high-pressure hoses. The supercritical carbon dioxide is temporarily prepared in the inner pipe, it is guaranteed that the carbon dioxide is in a supercritical state all the time when cracking a coal seam, and a good cracking effect is achieved; normal-temperature and normal-pressure carbon dioxide is used for displacing gas, the outer pipe is used for gas extraction, the problems of resource waste, gas leakage and the like caused by re-insertion of an extraction device are avoided, the amount of carbon dioxide discharged into air is reduced, and the device is safe, economical, environment-friendly and low in cost.

Description

Technical Field

[0001] The present invention relates to the field of coal seam gas extraction, and in particular to a carbon dioxide fracturing, displacement and gas extraction integrated device and an application method thereof. Background Art

[0002] my country's coal reservoirs are generally low-permeability coal seams with high gas content and severe coal mine gas disasters. At present, the main methods to increase the permeability of coal seams include mining liberation layers, hydraulic fracturing, hydraulic cutting, deep hole pre-splitting blasting, dense drilling, rotating water jet expansion, etc. These methods have achieved certain permeability enhancement effects when applied to low-permeability coal seams. Under certain conditions, the permeability enhancement effect is relatively ideal, but the current coalbed methane extraction rate is still low.

[0003] Although coal mine gas is an important cause of coal mine disasters, it is also a high-quality clean energy with great potential. CO2-driven coalbed methane (CO2-ECBM) combines carbon sequestration with improved coalbed methane recovery, and has multiple economic, resource and environmental benefits in promoting natural gas development and reducing greenhouse gas emissions. The coal-based energy structure is my country's basic national conditions. CO2-ECBM helps to solve and break through the bottleneck problems that restrict my country's clean and efficient use of coal and the development of new energy-saving technologies, promote the green and low-carbon transformation of energy in a scientific and orderly manner, and provide a solid energy guarantee for the high-quality development of the economy and society.

[0004] In addition, supercritical CO2 itself has the characteristics of low viscosity and high diffusivity of gas and high density of liquid. Its rupture pressure is lower than that of hydraulic fracturing and wave CO2 fracturing, and its rupture ability is stronger, resulting in a more complex fracture network. The critical conditions of CO2's critical temperature of 31.1℃ and critical pressure of 7.38MPa are easy to reach, so supercritical CO2 is a good physical blasting raw material.

[0005] Existing gas fracturing devices mostly use carbon dioxide gas, and there is little research on supercritical carbon dioxide. Its fracture pressure is lower than hydraulic fracturing and wave CO2 fracturing, and its fracture ability is stronger. However, it is difficult to ensure that carbon dioxide is always in a supercritical state. In addition, the existing fracturing displacement device is relatively cumbersome, and after the gas injection displacement is completed, the extraction device must be replaced for gas extraction, which cannot achieve the integrated operation of carbon dioxide fracturing, displacement and gas extraction.

[0006] Therefore, it is necessary to provide an integrated device and method for carbon dioxide fracturing, displacement and gas extraction to solve the above problems. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide an integrated device for carbon dioxide fracturing, displacement and gas extraction and an application method thereof. By temporarily preparing supercritical carbon dioxide in a fracturing tube, it is ensured that carbon dioxide is always in a supercritical state when fracturing the coal seam, thereby achieving a better fracturing effect. At the same time, carbon dioxide gas at normal temperature and pressure is used to replace gas to achieve integrated operation.

[0008] The technical solutions adopted are:

[0009] A carbon dioxide fracturing, displacement and gas extraction integrated device, comprising a controller, the device also comprising a fracturing and extraction device body, a gas source tank, a gas booster pump and a gas collection tank;

[0010] The main body of the fracturing and extraction device includes an inner tube and an outer tube, the inner tube is a fracturing tube and the outer tube is an extraction tube, the outer tube surrounds the outer circumference of the inner tube, and a carbon dioxide fracturing device is installed at the front end of the inner tube; the gas source tank is connected to the inner tube to the carbon dioxide fracturing device at the front end of the inner tube through a first mining high-pressure hose, and a gas booster pump is installed on the first mining high-pressure hose on the outer side of the inner tube; the gas collection tank is connected to the outer tube through a second mining high-pressure hose, and an automatic valve is installed on the second mining high-pressure hose; the gas booster pump and the automatic valve are connected to a controller and controlled by the controller.

[0011] The method of connecting the controller may be wireless connection, common practice in the prior art, remote control, etc.

[0012] Preferably, the end of the front end of the inner tube is arc-shaped, and the front end of the inner tube protrudes from the outer tube.

[0013] Preferably, the carbon dioxide fracturing device comprises an air inlet pipe, a liquid storage tank, a constant pressure rupture disc and a release head in sequence.

[0014] Preferably, an automatic safety valve is provided at the front end of the carbon dioxide fracturing device, and the automatic safety valve is connected to a controller and controlled by the controller.

[0015] Preferably, an automatic heating device, a temperature sensor and a pressure sensor are arranged inside the inner tube, and the automatic heating device, the temperature sensor and the pressure sensor are connected to a controller, and the temperature sensor and the pressure sensor transmit the temperature and pressure data inside the inner tube to the controller in real time.

[0016] Preferably, an opening is provided at the front end of the outer tube.

[0017] Preferably, the gas in the gas source tank is carbon dioxide gas.

[0018] An application method of a carbon dioxide fracturing, displacement and gas extraction integrated device comprises the following steps:

[0019] (1) Install the carbon dioxide fracturing device at the front end of the fracturing pipe and set an automatic safety valve; install the heating device, temperature sensor and pressure sensor into the pipeline of the fracturing pipe. The outside of the fracturing pipe surrounds the extraction pipe. The gas source tank is connected to the tail end of the fracturing pipe through the first mining high-pressure hose until it is connected to the air inlet pipe of the carbon dioxide fracturing device. The tail end of the extraction pipe is connected to the gas collection tank with a second mining high-pressure hose to assemble the fracturing and extraction device body;

[0020] (2) Install a gas booster pump on the first mining high-pressure hose between the fracturing pipe and the gas source tank; install an automatic valve on the second mining high-pressure hose between the extraction pipe and the gas collection tank;

[0021] (3) placing the main body of the fracturing and extraction device in a coal seam borehole and plugging the port of the coal seam borehole with a plugging device to make it airtight, delivering carbon dioxide gas from a gas source tank to the fracturing pipe, and obtaining supercritical carbon dioxide after being heated by an automatic heating device and pressurized by a gas booster pump. The supercritical carbon dioxide is released from the fracturing pipe to rupture the constant pressure rupture disc in the carbon dioxide fracturing device, thereby achieving fracturing of the mining coal seam;

[0022] (4) Turn off the automatic heating device and the gas booster pump, and transport carbon dioxide gas at room temperature and pressure from the gas source tank to the fracturing pipe to displace the gas in the coal seam through the carbon dioxide;

[0023] (5) After the displacement is completed, close the gas source tank, open the automatic valve on the second mining high-pressure hose, and start gas extraction. The gas enters the gas collection tank through the extraction pipe.

[0024] Preferably, the controller sets the pressure threshold in the carbon dioxide fracturing device to M, and the automatic heating device heats the carbon dioxide to 45-70°C to generate supercritical carbon dioxide; when the pressure in the carbon dioxide fracturing device exceeds the threshold M, the controller opens the automatic safety valve and automatically starts the pressure relief, so that the carbon dioxide released into the coal seam is in a supercritical state.

[0025] Preferably, the time for displacing the gas in the coal seam with carbon dioxide is 10 to 120 minutes.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention firstly adopts the method of temporarily preparing supercritical carbon dioxide in a fracturing tube, thereby ensuring that the carbon dioxide is always in a supercritical state when fracturing the coal seam, thereby achieving a better fracturing effect; secondly, carbon dioxide gas at normal temperature and pressure is injected into the coal seam through the fracturing tube. The adsorption capacity of coal for carbon dioxide is stronger than that for gas, and competitive adsorption can be formed to displace the gas in the coal, thereby avoiding the installation of a displacement pipeline, wasting space and cost, and saving the cost and energy of preparing supercritical carbon dioxide; finally, an extraction tube is used for gas extraction, thereby avoiding the problems of waste of resources and gas leakage caused by reinserting the extraction device.

[0028] The present invention injects carbon dioxide into coal seams, which can not only improve the gas recovery rate, but also reduce the amount of carbon dioxide discharged into the air. It is not only safe and economical, but also has a promoting effect on protecting the earth's ecological environment.

[0029] The device of the present invention is simple, easy to operate, low in cost, integrates carbon dioxide fracturing, displacement and gas extraction, has a high degree of automation and obvious effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural cutaway view of the device of the present invention.

[0031] In the figure, 1-coal seam drilling hole, 2-extraction pipe, 3-fracturing pipe, 4-carbon dioxide fracturing device, 5-release head, 6-constant pressure rupture disc, 7-automatic safety valve, 8-liquid storage tank, 9-air inlet pipe, 10-pressure sensor, 11-temperature sensor, 12-automatic heating device, 13-hole sealer, 14-second mining high-pressure hose, 15-automatic valve, 16-gas collection tank, 17-gas booster pump, 18-first mining high-pressure hose, 19-valve, 20-gas source tank. DETAILED DESCRIPTION

[0032] The accompanying drawings are only used for illustrative purposes and are only for the convenience of describing the present invention and simplifying the description, and should not be construed as limiting the present invention. In order to make the purpose, technical solution and beneficial effects of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0033] Example 1

[0034] A carbon dioxide fracturing, displacement and gas extraction integrated device, comprising a controller (the controller is a computer terminal), the device also includes a fracturing and extraction device body, a gas source tank 20, a gas booster pump 17 and a gas collection tank 16;

[0035] The main body of the fracturing and extraction device includes an inner tube and an outer tube, the inner tube is a fracturing tube 3, and the outer tube is an extraction tube 2, the outer tube surrounds the outer circumference of the inner tube, and a carbon dioxide fracturing device 4 is installed at the front end of the inner tube; the gas source tank 20 is connected to the inner tube to the carbon dioxide fracturing device 4 at the front end of the inner tube through a first mining high-pressure hose 18, and a gas booster pump 17 is installed on the first mining high-pressure hose 18 on the outer side of the inner tube; the gas collection tank 16 is connected to the outer tube through a second mining high-pressure hose 14, and an automatic valve 15 is installed on the second mining high-pressure hose 14; the gas booster pump 17 and the automatic valve 15 are connected to a controller and controlled by the controller.

[0036] The front end of the inner tube is arc-shaped, and the front end of the inner tube protrudes from the outer tube. The carbon dioxide fracturing device 4 includes an air inlet pipe 9, a liquid storage tank 8, a constant pressure rupture disc 6 and a release head 5 in sequence.

[0037] Example 2

[0038] A carbon dioxide fracturing, displacement and gas extraction integrated device, comprising a controller (the controller is a computer terminal), the device also includes a fracturing and extraction device body, a gas source tank 20, a gas booster pump 17 and a gas collection tank 16;

[0039] The main body of the fracturing and extraction device includes an inner tube and an outer tube, the inner tube is a fracturing tube 3, and the outer tube is an extraction tube 2, the outer tube surrounds the outer circumference of the inner tube, and a carbon dioxide fracturing device 4 is installed at the front end of the inner tube; the gas source tank 20 is connected to the inner tube to the carbon dioxide fracturing device 4 at the front end of the inner tube through a first mining high-pressure hose 18, and a gas booster pump 17 is installed on the first mining high-pressure hose 18 on the outer side of the inner tube; the gas collection tank 16 is connected to the outer tube through a second mining high-pressure hose 14, and an automatic valve 15 is installed on the second mining high-pressure hose 14; the gas booster pump 17 and the automatic valve 15 are connected to a controller and controlled by the controller.

[0040] The front end of the inner tube is arc-shaped, and the front end of the inner tube protrudes from the outer tube. The carbon dioxide fracturing device 4 includes an air inlet pipe 9, a liquid storage tank 8, a constant pressure rupture disc 6 and a release head 5 in sequence.

[0041] An automatic safety valve 7 is arranged at the front end of the carbon dioxide fracturing device 4, and the automatic safety valve 7 is connected to a controller and is controlled by the controller.

[0042] The inner tube is provided with an automatic heating device 12, which is heated by an electric coil and directly heats the metal workpiece, with high heating speed and efficiency. The automatic heating device 12 is connected to a controller and can be controlled by the controller to be turned on or off.

[0043] The front end of the outer tube is provided with an opening to facilitate the extraction of gas.

[0044] Example 3

[0045] like Figure 1 As shown, a carbon dioxide fracturing, displacement and gas extraction integrated device includes a controller (the controller is a computer terminal), the device also includes a fracturing and extraction device body, a gas source tank 20, a gas booster pump 17 and a gas collection tank 16;

[0046] The main body of the fracturing and extraction device includes an inner tube and an outer tube, the inner tube is a fracturing tube 3, and the outer tube is an extraction tube 2, the outer tube surrounds the outer circumference of the inner tube, and a carbon dioxide fracturing device 4 is installed at the front end of the inner tube; the gas source tank 20 is connected to the inner tube to the carbon dioxide fracturing device 4 at the front end of the inner tube through a first mining high-pressure hose 18, and a gas booster pump 17 is installed on the first mining high-pressure hose 18 on the outer side of the inner tube; the gas collection tank 16 is connected to the outer tube through a second mining high-pressure hose 14, and an automatic valve 15 is installed on the second mining high-pressure hose 14; the gas booster pump 17 and the automatic valve 15 are connected to a controller and controlled by the controller.

[0047] The front end of the inner tube is arc-shaped, and the front end of the inner tube protrudes from the outer tube. The carbon dioxide fracturing device 4 includes an air inlet pipe 9, a liquid storage tank 8, a constant pressure rupture disc 6 and a release head 5 in sequence.

[0048] An automatic safety valve 7 is arranged at the front end of the carbon dioxide fracturing device 4, and the automatic safety valve 7 is connected to a controller and is controlled by the controller.

[0049] An automatic heating device 12, a temperature sensor 11 and a pressure sensor 10 are arranged inside the inner tube. The automatic heating device 12, the temperature sensor 11 and the pressure sensor 10 are wirelessly connected to the controller, and the temperature sensor 11 and the pressure sensor 10 transmit the temperature and pressure data in the inner tube to the controller in real time. The automatic heating device 12 uses electric coil heating to directly heat the metal workpiece, and the heating speed is fast and the efficiency is high. The automatic heating device 12 is connected to the controller and can be controlled by the controller to be turned on or off.

[0050] The front end of the outer tube is provided with an opening to facilitate extraction of gas. The gas in the gas source tank 20 is carbon dioxide gas, which can be heated and pressurized to generate supercritical carbon dioxide to crack the coal seam and can also replace gas.

[0051] An application method of a carbon dioxide fracturing, displacement and gas extraction integrated device comprises the following steps:

[0052] (1) Install the carbon dioxide fracturing device 4 at the front end of the fracturing pipe 3 and set the automatic safety valve 7; install the heating device 12, the temperature sensor 11 and the pressure sensor 10 in the pipeline of the fracturing pipe 3. The outer side of the fracturing pipe 3 surrounds the extraction pipe 2. The gas source tank 20 is connected to the tail end of the fracturing pipe 3 through the first mining high-pressure hose 18 until it is connected to the air inlet pipe 9 of the carbon dioxide fracturing device 4. The tail end of the extraction pipe 2 is connected to the gas collection tank 16 through the second mining high-pressure hose 14 to assemble the fracturing and extraction device body.

[0053] (2) Install a gas booster pump 17 on the first mining high-pressure hose 18 between the fracturing pipe 3 and the gas source tank 20; install an automatic valve 15 on the second mining high-pressure hose 14 between the extraction pipe 2 and the gas collection tank 16;

[0054] (3) The main body of the fracturing and extraction device is placed in the coal seam borehole 1 and the port of the coal seam borehole is sealed with a sealer 13, and carbon dioxide gas is transported from the gas source tank 20 to the fracturing pipe 3. After being heated by the automatic heating device 12 and pressurized by the gas booster pump 17, supercritical carbon dioxide is obtained. The supercritical carbon dioxide is released from the fracturing pipe 3, causing the constant pressure rupture disc 6 in the carbon dioxide fracturing device to rupture, thereby achieving fracturing of the mining coal seam;

[0055] (4) Turn off the automatic heating device 12 and the gas booster pump 17, and deliver carbon dioxide gas at room temperature and pressure to the fracturing pipe 3 from the gas source tank 20, so as to displace the gas in the coal seam through the carbon dioxide;

[0056] (5) After displacement for 30 minutes, close the valve 19 on the gas source tank 20, open the automatic valve 15 on the second mining high-pressure hose 14, and start gas extraction. The gas enters the gas collection tank 16 through the extraction pipe 2.

[0057] The controller sets the pressure threshold in the carbon dioxide fracturing device to M (8MPa), and the automatic heating device heats the carbon dioxide to 60°C to generate supercritical carbon dioxide. The temperature sensor 11 and the pressure sensor 10 use wireless transmission to display the temperature and pressure in real time. When the temperature and pressure exceed the supercritical carbon dioxide generation value, they can help control the switch of the heating device and the boosting device; the automatic safety valve 7 can be automatically opened and closed according to the working pressure of the system.

[0058] When the pressure in the carbon dioxide fracturing device 4 exceeds the set pressure (8MPa), the pressure relief is automatically started to ensure that the carbon dioxide released into the coal seam is in a supercritical state;

[0059] When supercritical carbon dioxide fracturing is carried out, the gas booster pump 17 is turned on to pressurize the carbon dioxide gas. When the fracturing is completed and the carbon dioxide is used to displace coal seam gas, the gas booster pump 17 is turned off and atmospheric pressure carbon dioxide gas is injected into the fracturing pipe 3 from the gas source tank 20. When the fracturing and displacement work is carried out, the automatic valve 15 is closed, and when the displacement work is completed, the automatic valve 15 is opened to carry out gas extraction.

[0060] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A carbon dioxide fracturing, displacement and gas extraction integrated device, including a controller, characterized in that: The device also includes a fracturing and extraction device body, a gas source tank, a gas booster pump and a gas collection tank; The main body of the fracturing and extraction device includes an inner tube and an outer tube, the inner tube is a fracturing tube and the outer tube is an extraction tube, the outer tube surrounds the outer circumference of the inner tube, and a carbon dioxide fracturing device is installed at the front end of the inner tube; the gas source tank is connected to the inner tube to the carbon dioxide fracturing device at the front end of the inner tube through a first mining high-pressure hose, and a gas booster pump is installed on the first mining high-pressure hose on the outer side of the inner tube; the gas collection tank is connected to the outer tube through a second mining high-pressure hose, and an automatic valve is installed on the second mining high-pressure hose; the gas booster pump and the automatic valve are connected to a controller and controlled by the controller.

2. The integrated device for carbon dioxide fracturing, displacement and gas extraction according to claim 1, characterized in that: The end of the front end of the inner tube is in an arc shape, and the front end of the inner tube protrudes from the outer tube.

3. The integrated device for carbon dioxide fracturing, displacement and gas extraction according to claim 2, characterized in that: The carbon dioxide fracturing device comprises an air inlet pipe, a liquid storage tank, a constant pressure rupture disc and a release head in sequence.

4. The integrated device for carbon dioxide fracturing, displacement and gas extraction according to claim 3, characterized in that: An automatic safety valve is arranged at the front end of the carbon dioxide fracturing device, and the automatic safety valve is connected to a controller and is controlled by the controller.

5. The integrated device for carbon dioxide fracturing, displacement and gas extraction according to claim 3, characterized in that: An automatic heating device, a temperature sensor and a pressure sensor are arranged inside the inner tube, and the automatic heating device, the temperature sensor and the pressure sensor are connected to a controller, and the temperature sensor and the pressure sensor transmit the temperature and pressure data inside the inner tube to the controller in real time.

6. The integrated device for carbon dioxide fracturing, displacement and gas extraction according to claim 1, characterized in that: The front end of the outer tube is provided with an opening.

7. The integrated device for carbon dioxide fracturing, displacement and gas extraction according to claim 1, characterized in that: The gas in the gas source tank is carbon dioxide gas.

8. The method for applying the integrated device for carbon dioxide fracturing, displacement and gas extraction according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Install the carbon dioxide fracturing device at the front end of the fracturing pipe and set an automatic safety valve; install the heating device, temperature sensor and pressure sensor into the pipeline of the fracturing pipe. The outside of the fracturing pipe surrounds the extraction pipe. The gas source tank is connected to the tail end of the fracturing pipe through the first mining high-pressure hose until it is connected to the air inlet pipe of the carbon dioxide fracturing device. The tail end of the extraction pipe is connected to the gas collection tank with a second mining high-pressure hose to assemble the fracturing and extraction device body; (2) Install a gas booster pump on the first mining high-pressure hose between the fracturing pipe and the gas source tank; install an automatic valve on the second mining high-pressure hose between the extraction pipe and the gas collection tank; (3) The main body of the fracturing and extraction device is placed in the coal seam borehole and the port of the coal seam borehole is sealed with a sealer. Carbon dioxide gas is transported from the gas source tank to the fracturing pipe. After being heated by the automatic heating device and pressurized by the gas booster pump, supercritical carbon dioxide is obtained. The supercritical carbon dioxide is released from the fracturing pipe to rupture the constant pressure rupture disc in the carbon dioxide fracturing device, thereby achieving fracturing of the mining coal seam; (4) Turn off the automatic heating device and the gas booster pump, and transport carbon dioxide gas at room temperature and pressure from the gas source tank to the fracturing pipe to displace the gas in the coal seam through the carbon dioxide; (5) After the displacement is completed, close the gas source tank, open the automatic valve on the second mining high-pressure hose, and start gas extraction. The gas enters the gas collection tank through the extraction pipe.

9. The application method of the integrated device for carbon dioxide fracturing, displacement and gas extraction according to claim 8 is characterized in that: The controller sets the pressure threshold in the carbon dioxide fracturing device to M, and the automatic heating device heats the carbon dioxide to 45-70°C to generate supercritical carbon dioxide; when the pressure in the carbon dioxide fracturing device exceeds the threshold M, the controller opens the automatic safety valve and automatically starts the pressure relief, so that the carbon dioxide released into the coal seam is in a supercritical state.

10. The application method of the integrated device for carbon dioxide fracturing, displacement and gas extraction according to claim 8, characterized in that: The time for displacing gas in coal seams with carbon dioxide is 10 to 120 minutes.

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