Water-gas dispersion system injection device and method for CO2 liquid-state delayed conversion microbubbles

Abstract

The invention relates to a water-gas dispersion system injection device and method for CO2 liquid-state delayed conversion microbubbles. The problems of multiple injection processes and high construction and operation cost of a water-gas dispersion system in the prior art are solved. A water injection pipe penetrates through the center of the pressure-resistant outer cylinder; a plurality of porous vibrators are connected to a pipe body of the water injection pipe, and one side of each porous vibrator is communicated with the water injection pipe; the porous vibrator is connected with the gas injection pipe; the porous vibrator is connected with the controller; the injection method comprises the following steps: at a wellhead injection stage, stably dispersing CO2 in water in a liquid microsphere form; and a stage of converting the mixed liquid into microbubbles, wherein the mixed liquid in the process is converted into a water-gas dispersion system of the microbubbles. According to the method, CO2 is mixed with injected water in a liquid form, and is gradually converted into micron-sized bubbles in the process of moving into an oil reservoir in a shaft, a micron-sized water-gas dispersion system is formed and injected into the oil reservoir, the oil displacement effect is achieved, the injection process is greatly simplified, one set of water injection pump and gas injection pump can be shared by multiple wells, and the operation cost is greatly reduced.

Description

Technical Field:

[0001] The present invention relates to the technical field of oilfield development, and particularly to an injection device and method for a water-gas dispersion system with CO2 liquid delayed conversion into microbubbles. Background Art:

[0002] The water-gas dispersion system for enhanced oil recovery technology (a system that stably disperses tiny bubbles in an aqueous phase) is gradually applied in the oilfield site as an emerging technology and has achieved good results in increasing production. Therefore, the water-gas dispersion system for enhanced oil recovery technology has received more and more attention. The water-gas dispersion system is a mixed system formed by stably dispersing tiny bubbles in an aqueous phase. The current on-site implementation process is to install a water-gas dispersion device at the wellhead of the injection well. The injection water pipeline and the injection gas pipeline are respectively led to the vicinity of the wellhead. After being mixed by the water-gas dispersion device, a water-gas dispersion system is formed, and then the system flows along the wellbore to the reservoir in the form of a uniformly mixed liquid. The process is shown in Figure 1 as follows.

[0003] The above process requires high-pressure water injection and high-pressure gas injection devices to be equipped near the wellhead of the injection well, and it is necessary to lead transportation pipelines from the water injection station and the gas injection station, resulting in high construction and operation costs. This method is the configuration for each injection well. If there are multiple wells, corresponding multiple configurations are required, and the method of separate injection is adopted, which greatly increases the construction and operation costs. Summary of the Invention:

[0004] The object of the present invention is to overcome the problems in the background art that the injection process of the existing water-gas dispersion system is relatively complex and the construction and operation costs are high, and to provide an injection device for a water-gas dispersion system with CO2 liquid delayed conversion into microbubbles. In this injection device for a water-gas dispersion system with CO2 liquid delayed conversion into microbubbles, CO2 is mixed with the injection water in a liquid state, and gradually converts into micron-sized bubbles during the migration process in the wellbore towards the reservoir, forming a micron-sized water-gas dispersion system and injecting it into the reservoir to play the role of enhanced oil recovery, greatly simplifying the injection process of the water-gas dispersion system, enabling a set of injection water pumps and injection gas pumps to be shared by multiple wells, and significantly reducing the operation cost. The present invention also provides a method for injecting a water-gas dispersion system with CO2 liquid delayed conversion into microbubbles.

[0005] To achieve the above object, in the first aspect of the present invention, an injection device for a water-gas dispersion system with CO2 liquid delayed conversion into microbubbles is provided, including a pressure-resistant outer cylinder, and a water injection pipe is connected through the center of the pressure-resistant outer cylinder; several porous vibrators are connected to the pipe body of the water injection pipe, and one side of the porous vibrator is communicated with the water injection pipe; the porous vibrator is connected to an injection gas pipe; the porous vibrator is connected to a controller through a wire interface; the water injection pipe, the sealed pressure-resistant outer cylinder, the porous vibrator, the wire interface and the controller constitute a mixing pipe section.

[0006] Preferably, the porous vibrator includes a sealed housing, an ultrasonic oscillator is installed in the middle of the sealed housing, and a microporous plate is installed at the end of the ultrasonic oscillator; there is a gas inlet and a wire interface on one side of the sealed housing.

[0007] Preferably, the minimum configuration of the porous vibrator is 6;

[0008] They are arranged in an equilateral hexagon on the radial section of the pressure-resistant outer cylinder, 2 are arranged at the same position, and the two microporous plates face each other; the CO2 microspheres dispersed by a single porous vibrator show a conical distribution, and the hexagonal design makes the CO2 microspheres in the pipe section evenly distributed in the injected water.

[0009] Preferably, the microporous plate designs parameters such as the hole density and hole diameter according to the CO2 injection volume and the microbubble diameter requirements of the water-gas dispersion system; the microporous plate is made of titanium alloy, and the hole diameter is not affected by corrosion; the hole diameter is in the range of 10-100 μm, so that the generated microspheres are kept at the micron scale; the thickness of the microporous plate is in the range of 0.1-1 mm, so that the microporous plate has elastic vibration ability and cooperates with the vibration of the oscillator to disperse the liquid CO2.

[0010] On the other hand, the present invention provides a method for injecting a water-gas dispersion system of CO2 liquid delayed conversion microbubbles, including the following steps:

[0011] Step 1. The method for injecting a water-gas dispersion system of CO2 liquid delayed conversion microbubbles includes the following steps:

[0012] Step 1. Preparation work; determine the number of porous vibrators and assemble the injection device;

[0013] Step 2. Wellhead injection stage; CO2 is stably dispersed in water in the form of liquid microspheres

[0014] First, inject water according to the designed amount. After the injection water pressure is stable, open the gas injection valve and at the same time turn on the porous vibrator; adjust the gas injection volume to meet the gas-water ratio design. Inject water and gas media at the same time. After entering the stable injection stage; within the wellhead device and a limited depth into the wellbore, CO2 is stably dispersed in water in the form of liquid microspheres;

[0015] Step 3. Mixed liquid conversion to microbubble stage, the mixed liquid in the process is converted into a water-gas dispersion system of microbubbles;

[0016] The mixed liquid continues to move downward in the wellbore, the temperature gradually rises, CO2 is converted from a liquid state to a supercritical state (the state is similar to a gaseous state), the interface of the micron-sized bubbles is obvious, and the bubble diameter increases. The bubble diameter of the microbubbles generated by the gaseous CO2 by the microporous plate is usually in the range of 200-500 μm.

[0017] At a pressure of 10 MPa, at 30 °C, CO2 liquid microspheres with diameters of 1, 10, and 50 μm are transformed into CO2 microbubbles (supercritical state) at 80 °C, and the corresponding bubble diameters change to 1.6, 15.4, and 75.9 μm. When using the same microporous plate to generate microbubbles from gaseous CO2, the bubble diameters are usually in the range of 200 - 500 μm. Therefore, this method has a stronger and simpler ability to control the bubble diameter.

[0018] Preferably, the preparation work in step 1 includes: the method for determining the number of porous vibrators: according to the injection volume and gas-water ratio design, determine the number and related models of porous vibrators;

[0019] Preferably, the assembling of the injection device:

[0020] Install a mixing pipe section at the wellhead of the injection well, and connect the water injection pipe and the gas injection pipeline; to achieve the injection of CO2 in liquid state, the water injection pipe, the gas injection pipeline, and the wellhead device need to be controlled below 31.2 °C (below the critical temperature, CO2 is in liquid state at a pressure of 10 MPa); the water injection pipe of the injection device is connected to the incoming water injection pipeline of the wellhead device; the gas injection pipe of the injection device is connected to the gas injection pipeline of the wellhead device; the mixed liquid outlet of the injection device is connected to the inlet of the injection well.

[0021] Preferably, the method for entering the stable injection stage in step 2 is: observe the wellhead pressure gauge. After injecting water and gas media simultaneously, when the increase in wellhead pressure is in the range of 0.5 - 1 MPa, it can be considered that the stable injection stage has been entered;

[0022] Preferably, the limited depth within the wellbore in step 2 refers to a wellbore depth less than 100 m.

[0023] The principle of the injection method of the water-gas dispersion system with delayed conversion of CO2 liquid microbubbles in the present invention:

[0024] The difficult points of the existing water-gas dispersion system injection process are that when a gaseous medium (such as N2) is mixed with water in a dispersion device, it is easy to form large bubbles (see Figure 1 ), and strict control must be carried out on the bubble diameter generated. In addition, controlling the gas-water ratio is also an important method to prevent the merging of generated bubbles. According to the equal-volume spherical model calculation, the maximum gas-water ratio is 1:2. If you want to increase the gas-water ratio at the bottom of the well (high pressure, usually greater than 30 MPa) (close to the maximum gas-water ratio), it is more difficult to prevent the merging of generated bubbles.

[0025] Generally, the density difference of the same gas in gaseous and liquid states is relatively large. At a pressure of 10 MPa, at 30 °C, CO2 is in liquid state with a density of 0.77 g / mL; at 50 °C and 80 °C, CO2 is in supercritical state (gaseous) with densities of 0.38 g / mL and 0.22 g / mL respectively. For the same mass of gas, the volume expands by about 2 times and 4 times compared to the liquid state.

[0026] Obviously, if the mixing of water and gas medium (liquid state) is carried out under liquid conditions and then the gas medium is restored to the gaseous state in the wellbore and even in the reservoir, the number of bubble coalescence during the mixing process and the horizontal migration process can be significantly reduced. Therefore, a method of mixing CO2 with the injected water in a liquid environment and converting the liquid CO2 into microbubbles (supercritical state) at the bottom of the injection wellbore is designed. For the principle, see Figure 2 .

[0027] Figure 2 In [reference], the injected water is represented by a short horizontal line, and the CO2 is in a liquid state after being pressurized by a high-pressure pump and is represented by a large circle. The injected water and liquid CO2 are simultaneously injected into the mixing pipe section at a relatively small gas-water ratio. The liquid CO2 is dispersed into the injected water in the form of micron-sized spheres through the mixing action. At this time, the liquid CO2 is represented by small circles. Obviously, for the same mass of gas, the stability of the liquid mixture is stronger. After the mixture enters the wellbore and migrates towards the bottom of the well, as the depth increases and the geothermal temperature increases, the liquid CO2 in the mixture transitions to the supercritical state. During this process, the interface between CO2 and water becomes more obvious ( Figure 2 represented by a large circle in [reference]), and it is converted into micron-sized bubbles, forming a water-gas dispersion system.

[0028] The present invention may have the following beneficial effects compared with the above-mentioned background technology:

[0029] (1) A method for generating a water-gas dispersion system by delaying the conversion of liquid CO2 into micron-sized bubbles is invented. Compared with the gaseous generation method, the preparation ratio of the injected water and gas at the wellhead is compressed, the dispersion degree is more uniform, and the conversion process is easy to control.

[0030] (2) A mixing device for liquid CO2 and the injected water is invented. During the process of the injected water flowing towards the wellbore, the mixture remains in a uniform state and is gradually converted into microbubbles at the bottom of the wellbore.

[0031] (3) A mixing device for liquid CO2 and the injected water is invented, which simplifies the process of generating micron-sized bubbles.

[0032] (4) The method invented greatly simplifies the injection process of the water-gas dispersion system, and a set of injection water pumps and gas injection pumps can be shared by multiple wells, resulting in a significant reduction in operating costs. Description of the Drawings

[0033] Figure 1 is a schematic diagram of the injection process of the water-gas dispersion system displacement technology in the prior art of the present invention;

[0034] Figure 2 is a working principle diagram of the delayed conversion of liquid CO2 into microbubbles in the present invention;

[0035] Figure 3 is a schematic diagram of the injection device in the present invention;

[0036] Figure 4 is the cross-sectional view of the porous vibrator of the present invention;

[0037] Figure 5 is the distribution design diagram of the porous vibrator of the present invention;

[0038] Figure 6 is the schematic diagram of the working process of the CO2 liquid delayed conversion microbubble in the embodiment of the present invention. Specific embodiments:

[0039] To make the objectives, technical solutions and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in detail with reference to the accompanying drawings.

[0040] In the research on gas media in the water-gas dispersion system for enhanced oil recovery technology, it is found that CO2 is the most ideal gas. It not only forms microbubbles with small bubble diameters and a stable system, but also has a high degree of enhanced oil recovery. Currently, there are two ways to inject CO2. One is to inject gaseous CO2 into the wellbore by a high-pressure gas compressor (the wellhead pressure is usually not less than 10 MPa, while the gaseous CO2 gas source pressure is less than 4 MPa, so a high-pressure gas compressor needs to be equipped). The other is to inject liquid CO2 stored in a tank (the storage condition must be lower than the critical temperature of 31.2 °C and greater than the critical pressure of 7.38 MPa) into the wellbore by a high-pressure injection pump. The main advantages of the liquid injection method compared to the gaseous method are: high accuracy in transportation and injection metering; low operating cost of the liquid injection pump.

[0041] From the above analysis, it can be seen that if the liquid CO2 injection method can be combined with the water-gas dispersion system technology, the operating cost of the water-gas dispersion system injection will be significantly reduced.

[0042] The present invention analyzes the relevant problems to be solved in the combination of the two technologies, and adopts the method of CO2 liquid delayed conversion microbubbles, so that CO2 is mixed with the injection water in liquid form, and gradually converts into micron-sized bubbles during the migration from the wellbore to the reservoir, forming a micron-sized water-gas dispersion system and injecting it into the reservoir to play the role of enhanced oil recovery.

[0043] As Figure 3 shown, the present invention provides a water-gas dispersion system injection device for CO2 liquid delayed conversion microbubbles, including a pressure-resistant outer cylinder 1, and a water injection pipe 2 is inserted through the center of the pressure-resistant outer cylinder 1; a plurality of porous vibrators 3 are connected to the pipe body of the water injection pipe 2, and one side of the porous vibrator 3 is communicated with the water injection pipe; the porous vibrator is connected to an air injection pipe 4; the porous vibrator is connected to a controller 6 through an electric wire interface 5; a mixing pipe section is formed between the water injection pipe 2 and the porous vibrator 3 inside the sealed pressure-resistant outer cylinder 1;

[0044] As Figure 4 、 Figure 5As shown in the figure, the porous vibrator includes a sealed housing 7, an ultrasonic oscillator 8 is installed in the middle of the sealed housing 7, and a microporous plate 9 is installed at the end of the ultrasonic oscillator 8; there is a gas inlet 10 and a wire interface on one side of the sealed housing 7; the porous vibrator is connected to the injection pipe 4 through the gas inlet 10; and is connected to the controller 6 through the wire interface.

[0045] The minimum configuration of the porous vibrator is 6; it is arranged in an equilateral hexagon on the radial section of the pressure-resistant outer cylinder 1, 2 are arranged at the same position, and the two microporous plates face each other; the CO2 microspheres dispersed by a single porous vibrator show a conical distribution, and the hexagonal design makes the CO2 microspheres in the pipe section evenly distributed in the injected water.

[0046] The microporous plate is designed with parameters such as hole density and hole diameter according to the CO2 injection volume and microbubble diameter requirements of the water-gas dispersion system; the microporous plate is made of titanium alloy, and the hole diameter is not affected by corrosion; the hole diameter is in the range of 10-100 μm, so that the generated microspheres are kept at the micron scale; the thickness of the microporous plate is in the range of 0.1-1 mm, so that the microporous plate has the ability of elastic vibration, and cooperates with the vibration of the oscillator to disperse the liquid CO2. The vibration frequency of the ultrasonic oscillator is in the range of 20-200 kHz, and the power is in the range of 10-100 W.

[0047] The present invention provides a method for injecting a water-gas dispersion system for delaying the conversion of CO2 into microbubbles in a liquid state, including the following steps:

[0048] Step 1, preparation work; determine the number of porous vibrators and assemble the injection device;

[0049] According to the injection volume and the design of the gas-water ratio, determine the number and related models of the porous vibrators, assemble the mixing pipe section, and assemble the injection device.

[0050] Install the mixing pipe section at the wellhead of the injection well, and connect the injection water pipe and the injection gas pipeline.

[0051] The injection water pipe of the injection device is connected to the water injection pipeline of the wellhead device; the injection gas pipe of the injection device is connected to the injection gas pipeline of the wellhead device; the mixed liquid outlet of the injection device is connected to the injection well inlet.

[0052] To realize the injection of CO2 in a liquid state, the injection water pipe, the injection gas pipeline and the wellhead device need to be controlled below 31.2 °C (below the critical temperature, CO2 is in a liquid state under a pressure of 10 MPa). Usually, the CO2 gas storage station has a temperature control device and related implementation process capabilities.

[0053] Step 2, wellhead injection stage; CO2 is stably dispersed in water in the form of liquid microspheres

[0054] First, inject water according to the designed volume. After the injection pressure stabilizes, open the gas injection valve and at the same time turn on the porous vibrator. Adjust the gas injection volume to meet the designed gas-water ratio. Observe the wellhead pressure gauge. After injecting water and gas media simultaneously, if the increase in the wellhead pressure is within the range of 0.5 - 1 MPa, it can be considered that the stable injection stage has been entered. Within the wellhead device and within a limited depth of the wellbore (less than 100 m), CO2 is stably dispersed in water in the form of liquid microspheres.

[0055] Step 3: The stage of converting the mixed liquid into microbubbles, where the mixed liquid in this process is converted into a water-gas dispersion system of microbubbles;

[0056] The mixed liquid continues to flow downward, and the temperature gradually rises. CO2 is converted from a liquid state to a supercritical state (similar in form to a gas state). The interface of the micron-sized bubbles is obvious, and the bubble diameter increases. At a pressure of 10 MPa and a temperature of 30 °C, CO2 liquid microspheres with diameters of 1, 10, and 50 μm are converted into CO2 microbubbles (supercritical state) at 80 °C, and the corresponding changes in the bubble diameter are 1.6, 15.4, and 75.9 μm. The bubble diameter of the microbubbles generated from gaseous CO2 using the same microporous plate is usually in the range of 200 - 500 μm. Therefore, this method has a stronger and simpler ability to control the bubble diameter.

[0057] The mixed liquid in this process is converted into the existing water-gas dispersion system.

[0058] The following further illustrates the present invention with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0059] Embodiment 1

[0060] Through the application in a certain injection well, as Figure 6 shown, the injection method of the water-gas dispersion system with delayed conversion of CO2 liquid into microbubbles of the present invention is specifically described.

[0061] The wellhead pressure of this injection well is set at 10 MPa, the reservoir depth is 2000 m, the bottom-hole flowing pressure is 30 MPa under water injection conditions, and the bottom-hole temperature is 80 °C. At a pressure of 10 MPa, CO2 is in a liquid state at 30 °C with a density of 0.77 g / mL; CO2 is in a supercritical state (gas state) at 80 °C with a density of 0.22 g / mL.

[0062] (1) Preparation work

[0063] According to the designed injection volume and gas-water ratio, determine the number and related models of the porous vibrators, and assemble the mixing pipe section.

[0064] Six porous vibrators are configured; they are arranged in an equilateral hexagon on the radial section of the pressure-resistant outer cylinder 1, with two at the same position and the two microporous plate surfaces facing each other; the CO2 microspheres dispersed by a single porous vibrator show a conical distribution, and the hexagonal design makes the CO2 microspheres in the pipe section evenly distributed in the injected water.

[0065] The microplate is designed with parameters such as hole density and hole diameter according to the CO2 injection volume and microbubble diameter requirements of the water-gas dispersion system; the microplate is made of titanium alloy, and the hole diameter is not affected by corrosion; the hole diameter is in the range of 10-100 μm, so that the generated microspheres are kept in the micron scale; the thickness of the microplate is in the range of 0.1-1 mm, so that the microplate has the ability of elastic vibration, and cooperates with the vibration of the vibrator to disperse the liquid CO2. The vibration frequency of the ultrasonic vibrator is 200 kHz and the power is 100 W.

[0066] Install a mixing pipe section at the wellhead of the injection well to connect the water injection pipe and the gas injection pipeline. The water injection pipe of the injection device is connected to the water injection pipeline of the wellhead device; the gas injection pipe of the injection device is connected to the gas injection pipeline of the wellhead device; the mixed liquid outlet of the injection device is connected to the inlet of the injection well.

[0067] To achieve the injection of CO2 in liquid state, the water injection pipe, gas injection pipeline and wellhead device need to be controlled below 31.2 °C (below the critical temperature, CO2 is in liquid state under 10 MPa pressure). Usually, the CO2 gas storage station has temperature control devices and related implementation process capabilities.

[0068] (2) Wellhead injection stage

[0069] First, inject water according to the designed volume. After the water injection pressure is stable, open the gas injection valve and at the same time turn on the porous vibrator. Adjust the gas injection volume to meet the designed gas-water ratio. Observe the wellhead pressure gauge. After injecting water and gas media at the same time, if the increase in wellhead pressure is in the range of 0.5-1 MPa, it can be considered that the stable injection stage has been entered. In the wellhead device and within a limited depth of the wellbore (less than 100 m), CO2 is stably dispersed in water in the form of liquid microspheres.

[0070] (3) Transformation into microbubbles stage

[0071] The mixed liquid continues to flow downward, the temperature gradually rises, and CO2 is transformed from liquid state to supercritical state (the form is similar to gaseous state). The interface of the micron-sized bubbles is obvious and the bubble diameter increases. Under 10 MPa pressure, at 30 °C, the CO2 liquid microspheres with diameters of 1, 10, and 50 μm are transformed into CO2 microbubbles (supercritical state) at 80 °C, and the corresponding changes in bubble diameter are 1.6, 15.4, and 75.9 μm. While using the same microplate, the bubble diameter of the microbubbles generated by gaseous CO2 is usually in the range of 200-500 μm. Therefore, this method has stronger and simpler ability to control the bubble diameter.

[0072] The mixed liquid in this process is transformed into the existing water-gas dispersion system.

[0073] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of them. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. Although the specific implementation manners of the present invention have been described above, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications or deformations that can be made without creative labor on the basis of the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An injection device for a water-vapor dispersion system of CO2 liquid delayed conversion microbubbles, comprising a pressure-resistant outer cylinder (1), characterized in that: A water injection pipe (2) passes through the center of the pressure-resistant outer cylinder (1); several porous vibrators (3) are connected to the pipe body of the water injection pipe (2), and one side of the porous vibrator (3) is communicated with the water injection pipe; the porous vibrator is connected to an air injection pipe (4); the porous vibrator is connected to a controller (6); the water injection pipe (2) and the porous vibrator (3) in the sealed pressure-resistant outer cylinder (1) form a mixing pipe section.

2. The injection device for a water-vapor dispersion system of CO2 liquid delayed conversion microbubbles according to claim 1, characterized in that: The porous vibrator includes a sealed housing (7), an ultrasonic vibrator (8) is installed in the middle of the sealed housing (7), and a microporous plate (9) is installed at the end of the ultrasonic vibrator (8); there is a gas inlet (10) and a wire interface (5) on one side of the sealed housing (7); the porous vibrator is connected to the controller (6) through the wire interface (5); and is connected to the air injection pipe (4) through the gas inlet (10).

3. The injection device for a water-vapor dispersion system of CO2 liquid delayed conversion microbubbles according to claim 1 or 2, characterized in that: The minimum configuration of the porous vibrator is 6. They are arranged in an equilateral hexagon on the radial section of the pressure-resistant outer cylinder (1), with 2 at the same position and the two microporous plates facing each other; the CO2 microspheres dispersed by a single porous vibrator show a conical distribution, and the hexagonal design makes the CO2 microspheres in the pipe section evenly distributed in the injected water.

4. The injection device for a water-vapor dispersion system of CO2 liquid delayed conversion microbubbles according to claim 2, characterized in that: The microporous plate is designed for the hole density and hole diameter according to the CO2 injection volume and the required microbubble diameter in the water-gas dispersion system; the microporous plate is made of titanium alloy, and the hole diameter is not affected by corrosion; the hole diameter is in the range of 10-100 μm, so that the generated microspheres are kept at the micron scale; the thickness of the microporous plate is in the range of 0.1-1 mm, so that the microporous plate has the ability of elastic vibration and cooperates with the vibration of the vibrator to disperse the liquid CO2.

5. The injection device for a water-vapor dispersion system of CO2 liquid delayed conversion microbubbles according to claim 2, characterized in that: The vibration frequency of the ultrasonic vibrator is in the range of 20-200 kHz, and the power is in the range of 10-100 W.

6. A method for injecting a water-vapor dispersion system of CO2 liquid delayed conversion microbubbles using the device according to claim 1, characterized in that: It includes the following steps: Step 1, Preparation work, determine the number of porous vibrators and assemble the injection device. Step 2, Wellhead injection stage, CO2 is stably dispersed in water in the form of liquid microspheres. First, inject water according to the designed amount. After the water injection pressure is stable, open the gas injection valve and at the same time turn on the porous vibrator; adjust the gas injection volume to meet the designed gas-water ratio; inject water and gas media at the same time. After entering the stable injection stage, in the wellhead device and within a limited depth of the wellbore, CO2 is stably dispersed in water in the form of liquid microspheres. Step 3, Mixed liquid conversion to microbubble stage, the mixed liquid in this process is converted into a water-gas dispersion system of microbubbles. The mixed liquid continues to move downward in the wellbore, the temperature gradually rises, CO2 is converted from a liquid state to a supercritical state, the interface of the micron-sized bubbles is obvious, and the bubble diameter increases; the bubble diameter of the microbubbles generated by the gaseous CO2 by the microporous plate is usually in the range of 200-500 μm.

7. The method according to claim 1, characterized in that: The preparation work in Step 1 includes: The method for determining the number of porous vibrators: Determine the number of porous vibrators according to the injection volume and the designed gas-water ratio.

8. The method according to claim 1, characterized in that: For assembling the injection device, install the mixing pipe section at the wellhead of the injection well and connect the water injection pipe and the gas injection pipeline; to realize the liquid injection of CO2, the water injection, gas injection pipelines and the wellhead device need to be controlled below 31.2 °C. The water injection pipe of the injection device is connected to the water injection pipeline of the wellhead device for the incoming water. The gas injection pipe of the injection device is connected to the gas injection pipeline of the wellhead device. The mixed liquid outlet of the injection device is connected to the injection well inlet.

9. The method according to claim 1, characterized in that: The method for entering the stable injection stage in Step 2 is as follows: Observe the wellhead pressure gauge. After injecting water and gas media simultaneously, if the increase in wellhead pressure ranges from 0.5 to 1 MPa, it can be considered that the stable injection stage has been entered.

10. The method according to claim 1, characterized in that: The finite depth within the wellbore in Step 2 refers to a wellbore depth less than 100 m.

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