Nano-bubble generator, nano-bubble preparation method and method for improving recovery efficiency by using nano-bubbles

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to a nano bubble generator, a nano bubble preparation method and a method for improving recovery efficiency by using nano bubbles, the nano bubble generator comprises a bubble generator main body, a containing cup and at least one bubble water filter plate, the mesh apertures of the adjacent bubble water filter plates are different, and the containing cup is arranged in the containing cup. The mesh diameter of the bubble water filter plate close to the water inlet end is larger than that of the bubble water filter plate close to the water outlet end. According to the bubble water filter plate disclosed by the invention, nano bubble water is converted into the nano bubble water through an extrusion shearing effect and is extruded out of the meshes, large bubble water can be converted into the nano bubble water, and the gas mixing uniformity is good; by using the nano-bubble method, the injection pressure during water flooding is effectively improved, the swept volume is enlarged, the flowing direction of oil and water is microscopically regulated and controlled, the oil washing efficiency is improved, and residual oil which is difficult to extract by conventional water flooding is effectively displaced.

Description

Technical Field

[0001] This invention relates to the field of oil extraction technology, and in particular to a nanobubble generator, a method for preparing nanobubbles, and a method for enhancing oil recovery using nanobubbles. Background Technology

[0002] Since the beginning of global oil extraction, many oil fields have reached the late stage of development, but the recoverable reserves underground are still large. In order to improve the recovery rate of crude oil, countries around the world have been constantly exploring new methods and technologies. my country has abundant reserves of low-permeability oil reservoirs, with low-permeability oil fields accounting for more than 40% of the total reserves. In the early stages, water injection was often used for development. Due to the strong adsorption between crude oil and rock matrix and the limited fluidity of low-permeability oil reservoirs, the recovery rate of conventional extraction technologies is often low (less than 35% on average). Therefore, conventional water drive is not suitable for the development of low-permeability oil reservoirs. Summary of the Invention

[0003] The technical problem to be solved by this invention is: in order to solve the problem of low recovery rate in the prior art, this invention provides a nanobubble generator, a nanobubble preparation method and a method for improving the recovery rate using nanobubbles, which is suitable for the development of low-permeability reservoirs with permeability of 10mD to 50mD. The recovery rate is improved by nanobubbles at a low cost.

[0004] The technical solution adopted by this invention to solve its technical problem is: a nanobubble generator, comprising: a bubble generator body, a container cup, and at least one bubble water filter plate. The bubble generator body has a water inlet end and a water outlet end. The bubble water filter plate is installed on the bubble generator body along the water flow direction and is located between the water inlet end and the water outlet end. There is a gap between adjacent bubble water filter plates. The bubble water filter plate has multiple mesh holes. The mesh hole diameters of adjacent bubble water filter plates are different, and the mesh hole diameter of the bubble water filter plate closer to the water inlet end is larger than that of the bubble water filter plate closer to the water outlet end. The container is filled with water. The water inlet is connected to the container through a water inlet pipe, and the water outlet is connected to the container through a water outlet pipe. An air inlet pipe is provided on the water inlet pipe, and the air inlet pipe is connected to an external air supply device. Water enters the water inlet pipe, and gas enters the water inlet pipe through the air inlet pipe, mixing with the water in the water inlet pipe to form large bubble water. The large bubble water passes through the water inlet and through the bubble water filter plate. The nano bubble water converted by the bubble water filter plate enters the container through the water outlet and the water outlet pipe.

[0005] The specific technical effect is as follows: by setting at least one bubble water filter plate between the water inlet and water outlet of the bubble generator body, and the mesh diameter of the bubble water filter plate near the water inlet is larger than that of the bubble water filter plate near the water outlet, large bubble water is blocked, so that large molecular bubbles are blocked at the previous stage bubble water filter plate, and are transformed into nano bubble water through compression, impact and shearing and squeezed out from the mesh. It can transform large bubble water into nano bubble water, with simple structure and good gas mixing uniformity.

[0006] Furthermore, the mesh size of each of the bubble water filter plates ranges from 1μm to 50μm. The specific technical effect is that the mesh size of the bubble water filter plate is one of the most crucial factors determining the particle size of the generated bubbles. The smaller the mesh size, the smaller the average particle size of the generated bubbles, especially significantly increasing the yield of nanobubbles. Smaller pore sizes mean that more pores can be arranged per unit area, forming more and finer gas columns or gas flow films when gas passes through, greatly increasing the specific surface area of ​​gas-liquid contact.

[0007] Furthermore, the spacing between adjacent bubble water filter plates is 20mm to 30mm.

[0008] Furthermore, the bubble water filter plate is a ceramic membrane or a wire mesh membrane.

[0009] Furthermore, the nanobubble generator also includes a gas-liquid mixing pump, which is installed on the water inlet. The water inlet of the gas-liquid mixing pump is connected to the container cup via a water inlet pipe, and the air inlet of the gas-liquid mixing pump is connected to an external air supply device via an air inlet pipe. The specific technical advantages are: the gas-liquid mixing pump has a compact structure, small footprint, and is easier to install and maintain; the system automatically draws in the appropriate amount of gas according to the operating conditions, eliminating the need for cumbersome gas-water ratio adjustments; the integrated design reduces leakage and failure points, and improves the long-term operational reliability of the entire generator.

[0010] Furthermore, the main body of the bubble generator includes a main pipe and clamps, and the bubble water filter plate is installed on the main pipe via the clamps. Specifically, the clamp connection allows for the replacement of bubble water filter plates with different mesh sizes.

[0011] A method for preparing nanobubbles, comprising the following steps: using a nanobubble generator as described above. Preparation steps S1: Preparation before preparation: Rinse the main body of the bubble generator, the bubble water filter plate and the container cup two to three times with distilled water. Pour purified water into the container cup and set the temperature of the purified water to 20℃~80℃. Insert one end of the water inlet pipe and one end of the water outlet pipe into the container cup. Cover the mouth of the container cup with a plastic shield. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump to 0.4 MPa, turn on the gas-liquid mixing pump, set the gas injection rate to 25 mL / min or 50 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in the container is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water.

[0012] The specific technical effects are as follows: the nanobubble generator and the preparation method have advantages in terms of the concentration, size uniformity and energy consumption of the nanobubbles formed. After multiple cycles of shearing, nanobubble water is finally obtained in the container.

[0013] A method for enhancing oil recovery using nanobubbles is disclosed. The method involves using nanobubbles prepared by the nanobubble preparation method described above to enhance oil recovery. The experiment is conducted using a displacement testing device, which includes: a displacement pump, a first six-way valve, a first piston-type intermediate container, a second piston-type intermediate container, a second six-way valve, an inlet pressure gauge, a core holder, a confining pressure valve, and a produced fluid collector. The displacement pump is connected to the first six-way valve via a pipeline. The first and second piston-type intermediate containers are arranged in parallel. The first piston-type intermediate container contains simulated formation water, and the second piston-type intermediate container... The container is filled with nano-bubble water. One end of the first piston-type intermediate container is connected to the first six-way valve via a pipeline. One end of the second piston-type intermediate container is connected to the first six-way valve via a pipeline. The other end of the first piston-type intermediate container is connected to the second six-way valve via a pipeline. The second six-way valve is connected to the inlet of the core holder via a pipeline. The inlet pressure gauge is located near the inlet of the core holder. The confining pressure valve is located inside the core holder. The outlet of the core holder is connected to the produced fluid collector via a pipeline.

[0014] Furthermore, it includes the following steps: Displacement Step 1: Prepare the core to be tested, place the core into the core holder, and the core holder will hold and fix the core. The confining pressure valve is set inside the core holder and located on the outer periphery of the core. Connect the various devices in the displacement test device and check the sealing performance of the displacement test device. Step 2: Start the displacement pump and adjust the first and second six-way valves to allow the simulated formation water in the first piston-type intermediate container to enter the core holder at a constant flow rate of 0.5 ml / min. Perform a water flooding experiment on the core. The produced fluid collector is used to collect the produced fluid. The core inlet pressure is continuously monitored by the inlet pressure gauge. Samples of the produced fluid in the collector are collected periodically. Oil and water are separated by an oil-water separator. The volume of the separated oil is measured, and the oil concentration of the produced fluid is calculated. When the oil concentration in the produced fluid is basically stable and less than 2%, the water flooding experiment is considered to have reached the residual oil state. The water flooding experiment is stopped, and the water flooding recovery rate at this time is calculated. Step 3: After the water flooding experiment reaches the residual oil state, adjust the first six-way valve and the second six-way valve to allow the nanobubble water in the second piston intermediate container to enter the core holder at the same flow rate as the water flooding experiment. Perform nanobubble water flooding experiment on the core. Continuously monitor the core inlet pressure through the inlet pressure gauge. Collect produced fluid samples from the produced fluid collector at regular intervals. Separate oil and water through the oil-water separation device, measure the volume of the separated oil, and calculate the oil concentration of the produced fluid. Stop the nanobubble water flooding experiment after 20 min to 180 min and calculate the nanobubble water flooding recovery rate at this time. Step 4: Calculate the enhanced oil recovery rate of the nanobubble water flooding stage, i.e., the enhanced oil recovery rate of nanobubble water flooding minus the enhanced oil recovery rate of water flooding. Step 5: After the experiment is completed, the core is removed, cleaned with distilled water, and then stored.

[0015] The specific technical effects are as follows: First, the method of enhancing oil recovery utilizes nanobubbles, whose small particle size can increase seepage resistance and block pores through deformation; second, it utilizes the unique properties of nanobubbles, where nanobubble water, as a displacing fluid, easily undergoes cavitation under ultrasonic or pressure changes, releasing energy and thus stripping away crude oil; finally, nanobubbles effectively displace residual oil that is difficult to recover using conventional waterflooding through multiple mechanisms such as reducing oil-water interfacial tension, altering rock wettability, and reducing crude oil viscosity. Compared with conventional waterflooding, the average oil recovery rate is increased by about 2.1%, with a maximum increase of 4.6%.

[0016] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention sets at least one bubble water filter plate between the water inlet and the water outlet of the bubble generator body, and the mesh aperture of the bubble water filter plate near the water inlet is larger than that of the bubble water filter plate near the water outlet, which blocks the large bubble water, so that the large molecular bubbles are blocked at the previous bubble water filter plate, and are converted into nano bubble water through extrusion and shearing action and squeezed out from the mesh. It can convert large bubble water into nano bubble water, with simple structure and good gas mixing uniformity. (2) The method of improving oil recovery in this invention firstly utilizes the small particle size of nanobubbles, which can increase seepage resistance and block pores through deformation; secondly, it utilizes the unique characteristics of nanobubbles, where nanobubble water, as a displacing fluid, is prone to cavitation under ultrasonic or pressure changes, releasing energy and thus stripping crude oil; finally, nanobubbles effectively displace residual oil that is difficult to recover by conventional waterflooding through multiple mechanisms such as reducing oil-water interfacial tension, changing rock wettability, and reducing crude oil viscosity. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is a schematic diagram of the structure of the nanobubble generator of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the first bubble water filter plate of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of the second bubble water filter plate of the present invention.

[0021] Figure 4 This is a schematic diagram of the structure of the third bubble water filter plate of the present invention.

[0022] Figure 5 This is a schematic diagram of the structure of the fourth bubble water filter plate of the present invention.

[0023] Figure 6 This is a schematic diagram of the displacement test apparatus of the present invention.

[0024] Figure 7 This is a schematic diagram showing the recovery rate curves of nanobubble water flooding for three types of core samples according to the present invention.

[0025] Figure 8 This is a schematic diagram showing the injection pressure curves for the three types of core samples of the present invention.

[0026] Figure 9 This is a schematic diagram illustrating the water drive recovery rates of the three types of core samples presented in this invention.

[0027] Figure 10 This is a schematic diagram of the overall experimental recovery rate of the three types of core samples of the present invention.

[0028] Figure 11 This is a schematic diagram of the Jamin effect of the present invention.

[0029] Figure 12 This is a schematic diagram of the nanobubble stripping of crude oil according to the present invention.

[0030] In the diagram: 1. Bubble generator body; 101. Main pipe; 102. Clamp; 2. Container cup; 5. Bubble water filter plate; 501. First bubble water filter plate; 502. Second bubble water filter plate; 503. Third bubble water filter plate; 504. Fourth bubble water filter plate; 505. Mesh; 6. Gas-liquid mixing pump; 7. Displacement pump; 8. First six-way valve; 9. First piston-type intermediate container; 10. Second piston-type intermediate container; 11. Second six-way valve; 12. Inlet pressure gauge; 13. Core holder; 14. Produced fluid collector. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] like Figures 1 to 5The image shows a preferred embodiment of the nanobubble generator of the present invention. This embodiment of the nanobubble generator includes: a bubble generator body 1, a container 2, a gas-liquid mixing pump 6, and four bubble water filter plates 5. The four bubble water filter plates 5 are a first bubble water filter plate 501, a second bubble water filter plate 502, a third bubble water filter plate 503, and a fourth bubble water filter plate 504. The bubble generator body 1 has an inlet end and an outlet end. The first bubble water filter plate 501, the second... The third, fourth, and fifth bubble water filter plates 502, 503, and 504 are sequentially installed on the main body 1 of the bubble generator along the water flow direction, located between the inlet and outlet ends. There is a gap between adjacent bubble water filter plates 5. Each bubble water filter plate 5 has multiple mesh holes 505. The mesh hole diameters of adjacent bubble water filter plates 5 are different, and the mesh hole diameters of the bubble water filter plates 5 closer to the inlet end are larger than those of the bubble water filter plates 5 closer to the outlet end. The container 2 contains water, with its inlet connected to the gas-liquid mixing pump 6 and its outlet connected to the container 2 via an outlet pipe. The inlet of the gas-liquid mixing pump 6 is connected to the container 2 via an inlet pipe, and the inlet of the gas-liquid mixing pump 6 is connected to an external gas supply device via an inlet pipe. Water is pumped into the gas-liquid mixing pump 6, and gas is pumped into the gas-liquid mixing pump 6 via an inlet pipe. Water and gas mix in the gas-liquid mixing pump 6 to form large bubble water. The large bubble water passes through the inlet and then through the bubble water filter plate 5. The nano bubble water, after being converted by the bubble water filter plate 5, enters the container 2 through the outlet and outlet pipe. Therefore, compared to the method of using a gas pump and a water pump, which requires separate adjustment of the gas and water volumes, making operation complex and difficult to control, the gas-liquid mixing pump 6 has a compact structure, small footprint, and is easier to install and maintain. The system automatically draws in the appropriate amount of gas according to the working conditions, eliminating the need for cumbersome gas-water ratio adjustments. The integrated design reduces leakage and failure points, improving the long-term operational reliability of the entire generator. The impeller of the gas-liquid mixing pump 6 directly applies enormous shear force to the gas-liquid mixture, tearing the gas into extremely small bubbles. This shear strength is generally unmatched by separate gas pump and water pump designs, avoiding air resistance problems. In separate designs, when the gas volume is slightly high, air binding can easily form in the pipeline or at the water pump inlet, causing a sharp drop in water pump efficiency or even dry running. The gas-liquid mixing pump 6 is specifically designed to handle high gas-liquid ratio conditions and can operate stably and efficiently.

[0035] In a preferred embodiment, the pore size of the mesh 505 of each bubble water filter plate 5 ranges from 1 μm to 50 μm. Therefore, the size of the mesh 505 of the bubble water filter plate 5 is one of the most critical factors determining the particle size of the generated bubbles. The smaller the pore size of the mesh 505, the smaller the average particle size of the generated bubbles is usually, especially the yield of nanobubbles will increase significantly. Smaller pore size means that more pores can be arranged in a unit area. When gas passes through, more and finer gas columns or gas flow films will be formed, which greatly increases the specific surface area of ​​gas-liquid contact.

[0036] Specifically, the mesh size 505 on the first bubble water filter plate 501 is 50μm, the mesh size 505 on the second bubble water filter plate 502 is 30μm, the mesh size 505 on the third bubble water filter plate 503 is 10μm, and the mesh size 505 on the fourth bubble water filter plate 504 is 1μm.

[0037] More specifically, the first bubble water filter plate 501, the second bubble water filter plate 502, the third bubble water filter plate 503, and the fourth bubble water filter plate 504 all use wire mesh membranes. Nanobubbles can be obtained by placing four wire mesh membranes between the inlet and outlet ends of the bubble generator body 1. More preferably, nanobubbles can be obtained by placing only one ceramic membrane between the inlet and outlet ends. This is because ceramic membranes have finer and more uniform pores than wire mesh membranes, enabling the generation of more and smaller bubbles; wire mesh membranes are less expensive than ceramic membranes, so either ceramic membranes or wire mesh membranes can be selected for the bubble water filter plate 5 as needed.

[0038] In a preferred embodiment, the spacing between adjacent bubble water filter plates 5 is 20mm to 30mm. This design is adopted because the nanobubble clouds generated from adjacent bubble water filter plates 5 overlap and collide, causing small bubbles to merge into larger bubbles (aggregation effect), reducing the specific surface area and efficiency of the system. To maintain the same gas production rate within a confined space, the inlet pressure needs to be increased, leading to increased energy consumption. Therefore, adjacent bubble water filter plates 5 need to be spaced 20mm to 30mm apart to maintain the same gas production rate without increasing energy consumption.

[0039] In a preferred embodiment, the bubble generator body 1 includes a main pipe 101 and a clamp 102, and the bubble water filter plate 5 is installed on the main pipe 101 via the clamp 102. Thus, bubble water filter plates 5 with different mesh sizes 505 can be replaced through the connection of the clamp 102.

[0040] A method for preparing nanobubbles, comprising the following steps: (The method describes a nanobubble generator as described above.) Preparation steps S1: Preparation before preparation: Rinse the bubble generator body 1, bubble water filter plate 5 and container 2 two to three times with distilled water. Pour purified water into container 2 and set the temperature of the purified water to 20℃~80℃. Insert one end of the water inlet pipe and one end of the water outlet pipe into container 2. Cover the mouth of container 2 with a plastic shield. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 25 mL / min or 50 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water.

[0041] Therefore, the nanobubble generator and the preparation method have advantages in terms of the concentration, size uniformity and energy consumption of nanobubbles. After multiple cycles of shearing, nanobubble water is finally obtained in container 2.

[0042] Specifically, to test the effects of the pore size 505 of the bubble water filter plate 5, the temperature of the purified water, and the air injection rate on the particle size and number of generated nanobubbles, the following experiments were conducted: Examples 1 to 5 were used to test the effect of the pore size of the mesh 505 of the bubble water filter plate 5 on the particle size and number of generated nanobubbles: Example 1: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container 2 two to three times with distilled water. Pour 500ml of purified water into container 2 and set the temperature of the purified water to 50℃. Insert one end of the inlet pipe and one end of the outlet pipe into container 2. Cover the mouth of container 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select a ceramic membrane with a mesh size of 505 and a pore size of 1μm and install it on the main pipe 101 through clamp 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 25 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water; In preparation step S4, the particle size and number of nanobubble water obtained in container 2 were measured. The particle size was 28.21 nm, and the number of bubbles was 3.14 × 10⁻⁶. 8 ±2.17×107 per ml.

[0043] Example 2: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container cup 2 two to three times with distilled water. Pour 500ml of purified water into container cup 2 and set the temperature of the purified water to 50℃. Insert one end of the inlet pipe and one end of the outlet pipe into container cup 2. Cover the mouth of container cup 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select a ceramic membrane with a mesh size of 505 and a pore size of 10μm and install it on the main pipe 101 through clamp 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 25 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water; In preparation step S4, the particle size and number of nanobubble water obtained in container 2 were measured. The particle size was 58.77 nm, and the number of bubbles was 3.01 × 10⁻⁶. 8 ±3.52×10 7 per ml.

[0044] Example 3: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container cup 2 two to three times with distilled water. Pour 500ml of purified water into container cup 2 and set the temperature of the purified water to 50℃. Insert one end of the inlet pipe and one end of the outlet pipe into container cup 2. Cover the mouth of container cup 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select a ceramic membrane with a mesh size of 505 and a pore size of 30μm and install it on the main pipe 101 through clamp 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 25 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water; In preparation step S4, the particle size and number of nanobubble water obtained in container 2 were measured. The particle size was 288.1 nm, and the number of bubbles was 1.09 × 10⁻⁶. 8 ±2.96×10 7 per ml.

[0045] Example 4: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container cup 2 two to three times with distilled water. Pour 500ml of purified water into container cup 2 and set the temperature of the purified water to 50℃. Insert one end of the inlet pipe and one end of the outlet pipe into container cup 2. Cover the mouth of container cup 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select a ceramic membrane with a mesh size of 505 and a pore size of 50μm and install it on the main pipe 101 through clamp 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 25 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water; In preparation step S4, the particle size and number of nanobubble water obtained in container 2 were measured. The particle size was 297.1 nm, and the number of bubbles was 1.11 × 10⁻⁶. 7 ±1.46×10 7 per ml.

[0046] Example 5: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container cup 2 two to three times with distilled water. Pour 500ml of purified water into container cup 2 and set the temperature of the purified water to 50℃. Insert one end of the inlet pipe and one end of the outlet pipe into container cup 2. Cover the mouth of container cup 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select four ceramic membranes with mesh 505 apertures of 50μm, 30μm, 10μm and 1μm, and install them sequentially on the main pipe 101 along the water flow direction through clamp 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 25 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water; In preparation step S4, the particle size and number of nanobubble water obtained in container 2 were measured. The particle size was 64.9 nm, and the number of bubbles was 7.16 × 10⁻⁶. 8 ±2.58×10 7 per ml.

[0047] Comparative Example 1: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container cup 2 two to three times with distilled water. Pour 500ml of purified water into container cup 2 and set the temperature of the purified water to 50℃. Insert one end of the inlet pipe and one end of the outlet pipe into container cup 2. Cover the mouth of container cup 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select two ceramic membranes with a mesh size of 1μm and install them sequentially on the main pipe 101 along the water flow direction using clamps 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. In preparation step S2, the injection pressure of the gas-liquid mixing pump 6 is set to 0.4 MPa. The gas-liquid mixing pump 6 is started. Due to the dense structure of the ceramic membrane, the number of ceramic membranes is increased and the mesh size of adjacent ceramic membranes is the same. The injection pressure required by the gas-liquid mixing pump 6 increases significantly. However, the current injection pressure of the gas-liquid mixing pump 6 cannot meet the requirement, resulting in liquid flowing out of the outlet pipe. Therefore, nanobubbles are not generated.

[0048] Conclusion: Through Examples 1 to 5 and Comparative Example 1, it can be seen that the mesh size 505 of the bubble water filter plate 5 is one of the most critical factors determining the particle size of the generated bubbles. The smaller the mesh size 505, the smaller the average particle size of the generated bubbles is usually, and the yield of nanobubbles will increase significantly.

[0049] Examples 2, 6, and 7 were used to test the effect of purified water temperature on the particle size and number of generated nanobubbles: Example 6: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container cup 2 two to three times with distilled water. Pour 500ml of purified water into container cup 2 and set the temperature of the purified water to 20℃. Insert one end of the inlet pipe and one end of the outlet pipe into container cup 2. Cover the mouth of container cup 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select a ceramic membrane with a mesh size of 505 and a pore size of 10μm and install it sequentially on the main pipe 101 along the water flow direction through clamp 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 25 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water; Preparation step S4: The nanobubble water obtained in container 2 is tested for bubble size and number. The bubble size is 101.5 nm and the bubble number is 1.13 × 10⁻⁶. 8 ±9.3×10 7 per ml.

[0050] Example 7: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container cup 2 two to three times with distilled water. Pour 500ml of purified water into container cup 2 and set the temperature of the purified water to 80℃. Insert one end of the inlet pipe and one end of the outlet pipe into container cup 2. Cover the mouth of container cup 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select a ceramic membrane with a mesh size of 505 and a pore size of 10μm and install it sequentially on the main pipe 101 along the water flow direction through clamp 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 25 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water; In preparation step S4, the particle size and number of nanobubble water obtained in container 2 were measured. The particle size was 133.6 nm, and the number of bubbles was 1.2 × 10⁻⁶. 8±7.63×10 7 per ml.

[0051] Conclusion: As shown in Examples 2, 6 and 7, within the temperature range of 20°C to 80°C, as the temperature increases from 20°C to 50°C, the average particle size of the nanobubbles decreases from 100nm to 50nm. This phenomenon is attributed to the fact that the increase in temperature reduces the viscosity of the liquid and enhances the diffusion ability of gas molecules, thereby promoting the generation of smaller bubbles. When the temperature is further increased to 80°C, the average particle size of the nanobubbles increases slightly (about 130nm), which is due to the aggregation of bubbles caused by overheating.

[0052] Examples 2 and 8 were used to test the effect of gas injection rate on the particle size and number of generated nanobubbles: Example 8: Preparation step S1: Rinse the bubble generator body 1, bubble water filter plate 5 and container cup 2 two to three times with distilled water. Pour 500ml of purified water into container cup 2 and set the temperature of the purified water to 50℃. Insert one end of the inlet pipe and one end of the outlet pipe into container cup 2. Cover the mouth of container cup 2 with a plastic baffle. Connect the inlet of gas-liquid mixing pump 6 to the other end of the inlet pipe. Connect the air inlet of gas-liquid mixing pump 6 to an external air supply device through the air inlet pipe. Connect the outlet of gas-liquid mixing pump 6 to the inlet of bubble generator body 1. Select a ceramic membrane with a mesh size of 505 and a pore size of 10μm and install it sequentially on the main pipe 101 along the water flow direction through clamp 102. Connect the outlet of bubble generator body 1 to the other end of the outlet pipe. Preparation step S2: Set the injection pressure of the gas-liquid mixing pump 6 to 0.4 MPa, turn on the gas-liquid mixing pump 6, set the gas injection rate to 50 mL / min, and the circulation time to 20 min; In preparation step S3, the purified water in container 2 is repeatedly circulated and sheared for 20 minutes to obtain nano-bubble water; Preparation step S4: The nanobubble water obtained in container 2 is tested for bubble size and number. The bubble size is 229.4 nm and the bubble number is 1.73 × 10⁻⁶. 8 ±5.63×10 7 per ml.

[0053] Conclusion: As can be seen from Examples 2 and 8, when there is too much gas, it exceeds the shear capacity of the liquid. The gas cannot form a continuous and sufficiently strong gas film or gas flow in the orifice plate or shear zone. The generated bubbles are uneven and easily form intermittent large bubbles. The generation rate is extremely low and the efficiency is poor. The gas forms a continuous gas column or large bubbles in the main body 1 of the bubble generator. Excessive gas intake (gas injection rate of 50 mL / min) causes the particle size distribution to become wider.

[0054] A method for enhancing oil recovery using nanobubbles, applicable to the field of tertiary oil recovery technology, improves oil recovery by using nanobubbles prepared by the nanobubble preparation method as described in any of the above embodiments, wherein experiments are conducted using a displacement testing device. (See [link to relevant documentation]). Figure 6 As shown, the displacement test apparatus includes: a displacement pump 7, a first six-way valve 8, a first piston-type intermediate container 9, a second piston-type intermediate container 10, a second six-way valve 11, an inlet pressure gauge 12, a core holder 13, a confining pressure valve, and a produced fluid collector 14. The displacement pump 7 is connected to the first six-way valve 8 via a pipeline. The first piston-type intermediate container 9 and the second piston-type intermediate container 10 are arranged in parallel. The first piston-type intermediate container 9 contains simulated formation water, and the second piston-type intermediate container 10 contains nanobubble water. One end of the first piston-type intermediate container 9 is connected via a pipeline. The first six-way valve 8 is connected to the second piston-type intermediate container 9. One end of the second piston-type intermediate container 9 is connected to the first six-way valve 8 through a pipeline. The other end of the first piston-type intermediate container 9 is connected to the second six-way valve 11 through a pipeline. The second six-way valve 11 is connected to the inlet of the core holder 13 through a pipeline. The inlet pressure gauge 12 is located near the inlet of the core holder 13. The confining pressure valve is located inside the core holder 13. The outlet of the core holder 13 is connected to the produced fluid collector 14 through a pipeline.

[0055] Specifically, the following experiments were conducted on three types of low-permeability cores to test whether nanobubble water flooding could improve oil recovery. The three types of low-permeability cores were Core 1 (permeability 26 mD), Core 2 (permeability 36 mD), and Core 3 (permeability 50 mD): A method for enhancing oil recovery using nanobubbles includes the following steps: Displacement Step 1: Prepare the core to be tested. Place the core to be tested into the core holder 13. The core holder 13 clamps and fixes the core. The confining pressure valve is set inside the core holder 13 and located on the outer periphery of the core. Connect the various devices in the displacement test device and check the sealing of the displacement test device. The steps for preparing the core samples for the experiment are as follows: ① Measure and calculate the various physical properties of the target rock core, including length, diameter, volume, and mass; ②Wash the core thoroughly with distilled water to remove surface particles, then place it in an oven and dry it at 80℃ until constant weight; ③ Vacuum saturated oil treatment is performed on the core, the mass of the saturated oil is recorded, and then the porosity of the core is calculated; ④ Place the saturated crude oil core in a constant temperature chamber and keep it at 25°C for a period of time to allow the crude oil to be evenly distributed in the core pores; Step 2: Start the displacement pump 7, adjust the first six-way valve 8 and the second six-way valve 11 to allow the simulated formation water (it should be noted that the simulated formation water is a 2% KCl solution) in the first piston intermediate container 9 to enter the core holder 13 at a constant flow rate of 0.5 ml / min, and conduct a water drive experiment on the core. At this time, the produced fluid collector 14 is used to collect the produced fluid during the water drive experiment. The core injection pressure is continuously monitored by the inlet pressure gauge 12, and produced fluid samples are collected from the produced fluid collector 14 at regular intervals. The oil and water are separated by the oil-water separation device, the volume of the separated oil is measured, and the oil concentration of the produced fluid is calculated. When the oil concentration in the produced fluid is basically stable and less than 2% (that is, the water content exceeds 98%), it is determined that the water drive experiment has reached the residual oil state, the water drive experiment is stopped, and the water drive recovery rate at this time is calculated. Step 3: After the water flooding experiment reaches the residual oil state, adjust the first six-way valve 8 and the second six-way valve 11 to allow the nanobubble water in the second piston-type intermediate container 10 to enter the core holder 13 at the same flow rate as the water flooding experiment, and conduct the nanobubble water flooding experiment on the core. At this time, the produced fluid collector 14 is used to collect the produced fluid from the water flooding experiment stage and the nanobubble water flooding stage. The core injection pressure is continuously monitored through the inlet pressure gauge 12, and produced fluid samples in the produced fluid collector 14 are collected at regular intervals. The oil and water are separated by the oil-water separation device, the volume of the separated oil is measured, and the oil concentration of the produced fluid is calculated. The nanobubble water flooding experiment is stopped after 20 min to 180 min, and the recovery rate at this time is calculated, which is the recovery rate of the entire experiment. Step 4: Calculate the enhanced oil recovery rate of the nanobubble water flooding stage, which is the overall oil recovery rate minus the water flooding recovery rate. Step 5: After the experiment is completed, the core is removed, cleaned with distilled water, and then stored.

[0056] Experiments were conducted on three types of core samples using the above steps, and a schematic diagram of the recovery rate of nanobubble water drive was plotted (see...). Figure 7 A schematic diagram of the injection pressure curve (see) Figure 8 A schematic diagram of waterdrive recovery (see) Figure 9 A schematic diagram of the overall recovery rate of the experiment (see...) Figure 10 ), and thus, from Figure 7 It can be seen that the recovery rate curves of the three types of core samples show basically the same trend: first a rapid increase (representing the water drive stage), then a stable horizontal extension (representing that the oil concentration in the produced fluid is basically stable and less than 2% during the water drive stage, indicating that the water drive experiment has reached the residual oil state), and finally a slow increase (representing the nanobubble water drive stage); from Figure 8It can be seen that the injection pressure curves of the three types of core samples have basically the same trend, all showing a rapid increase followed by a stable horizontal extension (representing the water drive stage), and then a rapid increase again (representing the nanobubble water drive stage); from Figure 9 As shown, the recovery rates of the three types of core samples during the water-drive stage basically conform to the fitted curve y1=0.346x+54.06, R 2 =0.1661, where x represents permeability, y1 represents the recovery rate during the waterflooding stage, and R 2 Represents the coefficient of determination; from Figure 10 As shown, the recovery rates of the three types of core samples throughout the experiment basically conformed to the fitted curve y2=0.3668x+56.026, R 2 =0.2051, where x represents permeability, y2 represents the recovery rate of the entire experiment, and R 2 This represents the coefficient of determination.

[0057] Experimental conclusion: The above experimental results show that the use of nanobubble flooding can improve the recovery rate of core samples, effectively increase the injection pressure of the core holder 13, thereby expanding the swept volume and improving the recovery rate.

[0058] In other words, during the oil displacement process, see Figure 11 As shown, nanobubbles in a water-gas dispersion system can increase seepage resistance and block pores through deformation. When nanobubbles flow through porous media, they need to deform to pass through narrow pore throats, which can cause them to become stuck. For example, when the bubble size is larger than or close to the pore throat size, it requires enormous pressure to squeeze through, and may even be completely stuck, forming an effective microscopic blockage. Although individual nanobubbles are very small, they tend to aggregate in narrow pores to form bubble clusters, which can also produce the Jamin effect, forming a gas-liquid two-phase interface and increasing the resistance to gas flow. This resistance can change the fluid path, forcing the subsequent displacement fluid into the unaffected low-permeability area, allowing the remaining oil to enter the mainstream channel and become flowable oil, thus expanding the swept volume and improving the recovery rate.

[0059] See Figure 12As shown, nanobubbles attached to oil films or rock surfaces can rupture (or undergo rapid size changes) under specific conditions, generating localized energy that disrupts the stability of the oil-rock interface, thereby stripping crude oil from the rock surface. Nanobubble rupture often works synergistically with the Jamin effect and changes in rock wettability. During displacement, even minor fluctuations in pressure, temperature, or fluid chemistry can cause nanobubble instability, including Oswald ripening, coalescence, and direct rupture. When nanobubbles (especially those attached to hard surfaces) rupture or contract rapidly, their interfacial potential energy is released instantaneously, generating microjets and localized shock waves. The energy of these microjets and shock waves acts on the oil-rock interface. The microjets exert a direct, shearing force on the oil film, pointing towards the rock surface, like a microscale water jet, prying or washing away the oil film. Crude oil adheres to the rock due to the adhesion work between the two; the energy released by the rupture of nanobubbles instantaneously provides the energy needed to overcome this adhesion work, causing the crude oil to bounce off or detach from the rock surface.

[0060] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention provides at least one bubble water filter plate 5 between the water inlet and the water outlet of the bubble generator body 1, and the mesh 505 aperture of the bubble water filter plate 5 near the water inlet is larger than the mesh 505 aperture of the bubble water filter plate 5 near the water outlet, thereby blocking the large bubble water and causing the large molecular bubbles to be blocked at the previous stage bubble water filter plate 5. Through compression and impact, they are converted into nano bubble water and squeezed out from the mesh 505. The large bubble water can be converted into nano bubble water. The structure is simple and the gas mixing uniformity is good. (2) The method of improving oil recovery of the present invention firstly utilizes the small particle size of nanobubbles, which can increase seepage resistance and block pores through deformation; secondly, it utilizes the unique characteristics of nanobubbles, where nanobubble water, as a displacement fluid, is prone to cavitation under ultrasonic or pressure changes, releasing energy and thus stripping crude oil; finally, nanobubbles effectively increase the injection pressure during water flooding, expand the swept volume, microscopically control the flow direction of oil and water, and improve the oil washing efficiency through multiple mechanisms such as reducing the interfacial tension between oil and water, changing the wettability of rocks, and reducing the viscosity of crude oil. (3) The injected high-pressure nanobubble water can effectively replenish the formation energy that is generally insufficient in low-permeability oil reservoirs; (4) Water and gas are the main media, no expensive chemical agents are required, the cost is low and there is no pollution to the environment; (5) Compared with continuous gas phase drive, gas in the form of nanobubbles is less prone to crossflow and can improve sweep efficiency. Although continuous gas phase can easily pass through large pore throats with almost no obstruction, the viscosity of displacing gases such as natural gas or nitrogen is extremely low and they flow very easily. The flow rate of gas is much higher than that of crude oil and water, and the gas breaks through in advance, forming crossflow. Nanobubbles have a key characteristic: they are easier to enter and block large pores with high permeability. Because bubbles and foaming agents will preferentially choose the path of least resistance (i.e., high permeability strips), a large number of bubbles will be generated there. These bubbles greatly increase the flow resistance of high permeability channels. Once the high permeability channels are effectively blocked, the subsequent displacing fluid (whether it is water or the bubbles themselves) is forced to turn to the low permeability area that was not originally swept. This greatly improves the macroscopic sweep efficiency and achieves planar profile modification and longitudinal profile modification, that is, the effect of expanding the sweep volume. Nanobubble water drive is less prone to crossflow than ordinary gas drive. Essentially, nanobubble water drive transforms the continuous and easily flowable gas phase into a dispersed, high-viscosity bubble system that can produce the Jamin effect.

[0061] The above description is based on the preferred embodiments of the present invention. Through the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the contents of the specification, but must be determined by the scope of the claims.

Claims

1. A nanobubble generator, characterized by, The nanometer bubble generator comprises a bubble generator body, a containing cup and at least one bubble water filter plate. The bubble generator body has a water inlet end and a water outlet end, the bubble water filter plates are arranged on the bubble generator body along the water flow direction and between the water inlet end and the water outlet end, the bubble water filter plates have a spacing between adjacent bubble water filter plates, the bubble water filter plates are provided with a plurality of mesh holes, the mesh hole diameters of adjacent bubble water filter plates are different, and the mesh hole diameter of the bubble water filter plate close to the water inlet end is larger than the mesh hole diameter of the bubble water filter plate close to the water outlet end. The containing cup is provided with water, the water inlet end is communicated with the containing cup through a water inlet pipe, the water outlet end is communicated with the containing cup through a water outlet pipe, the water inlet pipe is provided with an air inlet pipe, the air inlet pipe is communicated with an external air supply device, water enters the water inlet pipe, gas enters the water inlet pipe through the air inlet pipe, and the water in the water inlet pipe is mixed with the gas to form large bubble water, the large bubble water passes through the water inlet end and the bubble water filter plates, and the nanometer bubble water converted by the bubble water filter plates enters the containing cup through the water outlet end and the water outlet pipe. The mesh hole diameter of each bubble water filter plate ranges from 1 μm to 50 μm.

2. The nano bubble generator of claim 1, wherein The spacing between adjacent bubble water filter plates ranges from 20 mm to 30 mm.

3. The nano bubble generator of claim 1, wherein The bubble water filter plate is a ceramic membrane or a silk screen membrane.

4. The nano bubble generator of claim 1, wherein The nanometer bubble generator further comprises a gas-liquid mixing pump, the gas-liquid mixing pump is arranged on the water inlet end, the water inlet of the gas-liquid mixing pump is communicated with the containing cup through a water inlet pipe, and the air inlet of the gas-liquid mixing pump is communicated with an external air supply device through an air inlet pipe.

5. The nano bubble generator of claim 1, wherein The bubble generator body comprises a main pipe and a clamp, and the bubble water filter plates are arranged on the main pipe through the clamp.

6. The nano bubble generator of claim 1, wherein The method comprises the following steps:

7. A method for producing nanobubbles using the nanobubble generator according to any one of claims 1 to 6, wherein Preparation step S1, preparation preparation: using distilled water to flush the bubble generator body, the bubble water filter plate and the containing cup for two to three times, injecting purified water into the containing cup, setting the temperature of the purified water to 20-80℃, inserting one end of the water inlet pipe and one end of the water outlet pipe into the containing cup, and covering the plastic shielding plate on the cup mouth of the containing cup; Preparation step S2: setting the injection pressure of the gas-liquid mixing pump to 0.4 MPa, opening the gas-liquid mixing pump, setting the air injection rate to 25 mL / min or 50 mL / min, and setting the circulation time to 20 min; Preparation step S3: after the purified water in the containing cup is repeatedly circulated and sheared for 20 min, nanometer bubble water is obtained. ​ 8. A method for enhancing recovery using nanobubbles, wherein the nanobubbles produced by the nanobubble production method according to claim 7 are used to enhance recovery, characterized by, The experiment is carried out through a displacement test device, the displacement test device comprising a displacement pump, a first six-way valve, a first piston type intermediate container, a second piston type intermediate container, a second six-way valve, an inlet pressure gauge, a core holder, a confining pressure valve and an effluent collector, the displacement pump being connected with the first six-way valve through a pipeline, the first piston type intermediate container and the second piston type intermediate container being arranged in parallel, the first piston type intermediate container being filled with simulated formation water, the second piston type intermediate container being filled with nano bubble water, one end of the first piston type intermediate container being connected with the first six-way valve through a pipeline, one end of the second piston type intermediate container being connected with the first six-way valve through a pipeline, the other end of the first piston type intermediate container being connected with the second six-way valve through a pipeline, the other end of the second piston type intermediate container being connected with the second six-way valve through a pipeline, the second six-way valve being connected with the inlet of the core holder through a pipeline, the inlet pressure gauge being arranged close to the inlet of the core holder, the confining pressure valve being arranged in the core holder, and the outlet of the core holder being connected with the effluent collector through a pipeline.

9. The method for enhanced recovery using nanobubbles according to claim 8, wherein, The method comprises the following steps: Displacement step one, preparing the core to be tested, placing the core into the core holder, clamping and fixing the core by the core holder, arranging the confining pressure valve in the core holder and outside the core, and connecting each device in the displacement test device to detect the sealing property of the displacement test device; Displacement step two, starting the displacement pump, adjusting the first six-way valve and the second six-way valve to make the simulated formation water in the first piston type intermediate container enter the core holder at a constant flow rate of 0.5 ml / min to carry out water flooding experiment on the core, collecting the effluent by the effluent collector, continuously monitoring the inlet pressure of the core by the inlet pressure gauge, collecting effluent samples in the effluent collector at regular time intervals, separating oil and water by an oil-water separation device, measuring the volume of the separated oil, calculating the oil concentration of the effluent, and determining that the water flooding experiment reaches the residual oil state when the oil concentration of the effluent is basically stable and less than 2%, stopping the water flooding experiment, and calculating the water flooding recovery rate at this time; Displacement step three, after the water flooding experiment reaches the residual oil state, adjusting the first six-way valve and the second six-way valve to make the nano bubble water in the second piston type intermediate container enter the core holder at the same flow rate as the water flooding experiment to carry out nano bubble water flooding experiment on the core, continuously monitoring the inlet pressure of the core by the inlet pressure gauge, collecting effluent samples in the effluent collector at regular time intervals, separating oil and water by an oil-water separation device, measuring the volume of the separated oil, calculating the oil concentration of the effluent, and stopping the nano bubble water flooding experiment after 20 min to 180 min, and calculating the nano bubble water flooding recovery rate at this time; Displacement step four, calculating the enhanced recovery rate in the nano bubble water flooding stage, i.e. the nano bubble water flooding recovery rate minus the water flooding recovery rate; Displacement step five, after the experiment is completed, taking out the core, and cleaning and storing the core with distilled water.

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