Experimental device and method for water-oil visual displacement in pore-level microchannel

Abstract

The invention belongs to the technical field of oil reservoir exploitation, and particularly relates to an experimental device and method for water-oil visual displacement in a pore-level microchannel, a micro-fluidic chip is arranged to generate a single liquid drop, the length of the liquid drop is regulated and controlled, different capillary models are arranged to simulate rock cores with different pores, and the water-oil visual displacement in the pore-level microchannel is realized. Visual observation of the oil-water front propulsion law and the droplet migration form in the displacement process is achieved, and key data support is provided for studying the microscopic seepage mechanism in oil reservoir exploitation.

Description

Technical Field

[0001] The present invention belongs to the technical field of reservoir exploitation, and particularly relates to an experimental device and method for visual water-oil displacement in pore-level microchannels. Background Art

[0002] In recent years, the production of conventional oil and gas reservoirs has been growing weakly, entering a stage of "high proven reserves, low production growth". A reservoir is essentially a porous medium for storing and extracting hydrocarbons. At the same time, water also exists in the reservoir, resulting in multiphase flow of oil and water. After drilling, due to the natural energy of the reservoir, oil initially flows towards the surface. Subsequently, energy needs to be replenished to maintain the pressure gradient, during which a large amount of liquid invasion may occur, leading to severe water flooding in the well. This causes the continuous oil phase in the pores to transform into a discontinuous oil phase, and the discontinuous oil phase remains in the pores as residual oil, resulting in a decrease in the oil washing efficiency and thus affecting the recovery efficiency. Currently, most of the research on the mechanism of oil-water migration in porous media focuses on the deformation phenomena during fluid migration under different conditions, and generally uses numerical simulation methods for research. However, there is little research on the microscopic mechanism of fluid migration from the physical and chemical properties of the channel and the fluid itself through physical simulation under different displacement conditions.

[0003] Chinese Patent CN105422079A discloses a dynamic visualization observation device for displacement experiments, which observes the dynamic migration of oil and water in different reservoir types through different core thin sections, observes the dynamic migration of oil and water during the displacement process of different injection systems by changing the injection system, and can also observe the distribution of residual oil and remaining oil after the displacement, so as to formulate targeted oil reservoir exploitation and enhanced oil recovery plans. Although this dynamic visualization observation device can observe the laws of oil-water migration and the distribution of oil and water in real time, it cannot study the flow characteristics of single droplets in pores; in addition, the raw material of the visualized microscopic model is polydimethylsiloxane, which is hydrophobic, so surface hydrophilization treatment is usually required during the production process to enhance the interfacial properties with the fluid; more importantly, as a basic cross-section, a circle plays a crucial role in the study of the flow characteristics of single droplets in microchannels, while the visualized microscopic model in the patent cannot make the cross-section of the microchannel circular, and thus cannot study the phenomenon of single oil droplet migration of oil droplets in a circular cross-section microchannel. Summary of the Invention

[0004] To solve the above problems, the present invention provides an experimental device and method for visual water-oil displacement in pore-level microchannels, which generate single droplets and regulate the droplet length by setting a microfluidic chip, and simulate cores with different pores by setting different capillary models to realize the visual observation of the advancing law of the oil-water front and the migration morphology of droplets during the displacement process.

[0005] An experimental device for visual displacement of water-oil in pore-level microchannels, comprising: A constant-pressure pump channel and an observation channel; An air compressor 1 and a constant-pressure pump 3 are sequentially arranged on the constant-pressure pump channel; the constant-pressure pump 3 has real-time response ability to ensure the precise establishment and cut-off of the system pressure instantaneously, so as to realize the controllability of the droplet length; A microfluidic chip 6, a capillary model 7 and a liquid discharge port are sequentially arranged on the observation channel; The constant-pressure pump channel is connected to the observation channel through a water channel and an oil channel, and the water channel and the oil channel are connected in parallel.

[0006] A water storage tank 5 and a four-way joint 14 are sequentially arranged on the water channel; The four-way joint 14 is respectively connected to the water storage tank 5, the microfluidic chip 6, a constant-speed pump 9 and the capillary model 7; An oil storage tank 4 is arranged on the oil channel.

[0007] Preferably, a waste liquid pool 13 is further arranged below the liquid discharge port.

[0008] Preferably, the microfluidic chip 6 includes a microfluidic chip water inlet 601, a microfluidic chip oil inlet 602 and a microfluidic chip liquid outlet 603; The microfluidic chip water inlet 601 and the microfluidic chip oil inlet 602 are respectively connected to the water channel and the oil channel; The microfluidic chip liquid outlet 603 is connected to the capillary model 7.

[0009] Preferably, a micro syringe is arranged in the constant-speed pump 9.

[0010] Preferably, a first pressure sensor 10 is arranged between the four-way joint 14 and the capillary model 7, and a second pressure sensor 11 is arranged between the capillary model 7 and the liquid discharge port, for monitoring the pressure change at both ends of the capillary model 7.

[0011] Preferably, the first pressure sensor 10 is connected to an observation pipeline through a second three-way joint 24; Preferably, the second pressure sensor 11 is connected to an observation pipeline through a first three-way joint 8.

[0012] Preferably, a first one-way valve 15 and a first stop valve 17 are sequentially arranged between the oil storage tank 4 and the microfluidic chip 6; A second one-way valve 16 and a second stop valve 18 are sequentially arranged between the water storage tank 5 and the four-way joint 14; A third stop valve 19 is arranged between the constant-speed pump 9 and the four-way joint 14; A fourth stop valve 20 is arranged between the four-way joint 14 and the microfluidic chip 6; A fifth stop valve 21 is provided between the four-way joint 14 and the first pressure sensor 10.

[0013] Preferably, the microfluidic chip 6, the capillary model 7, and the waste liquid pool 13 are arranged on an optical flat plate for shockproofing and height adjustment.

[0014] Preferably, an industrial camera 12 is arranged above the optical flat plate for capturing experimental images.

[0015] Preferably, a planar light source 23 is arranged beside the optical flat plate to provide light for the industrial camera 12; the industrial camera 12 controls the field of view of the industrial camera 12 through a sliding table to realize image acquisition of the microfluidic chip 6 and the capillary model 7.

[0016] The first pressure sensor 10, the second pressure sensor 11, and the industrial camera 12 are all connected to the computer 22 to realize data acquisition and storage.

[0017] Preferably, the microfluidic chip 6 and the second three-way joint 24 are connected by an L-shaped stainless steel needle.

[0018] Preferably, a pressure gauge 2 is arranged between the air compressor 1 and the constant pressure pump 3 to monitor the pressure provided by the air compressor 1.

[0019] Preferably, the air compressor 1, the pressure gauge 2, and the constant pressure pump 3 are connected by a PU air pipe, and the constant pressure pump 3 is connected to both the oil storage tank 4 and the water storage tank 5 by a PU air pipe; more preferably, the inner diameter of the PU air pipe is 4 mm.

[0020] Preferably, the pipes of the oil channel and the water channel are both PTFE pipes; more preferably, the inner diameter of the PTFE pipe is 0.8 mm.

[0021] The capillary model 7 can be set as a single glass capillary or two or more capillaries in parallel to realize the true simulation of formation cores under different conditions.

[0022] Furthermore, the present invention also provides an experimental method for water-oil visualization displacement using the above experimental device, including: S1. Pretreatment: Clean the experimental device, connect the computer 22, adjust the industrial camera 12 and the light source, inject formation water into the water storage tank 5 and inject an oil sample into the oil storage tank 4. S2. Bubble discharge: Close the first stop valve 17, the third stop valve 19, and the fifth stop valve 21, and open the second stop valve 18 and the fourth stop valve 20; close the constant speed pump 9, open the air compressor 1 and the constant pressure pump 3, and inject the formation water in the water storage tank 5 into the observation channel until formation water appears at the liquid discharge port. Close the first stop valve 17, the second stop valve 18, and the fourth stop valve 20, and open the third stop valve 19 and the fifth stop valve 21; close the air compressor 1 and the constant pressure pump 3, open the constant speed pump 9, and inject formation water into the observation channel through the microinjector of the constant speed pump 9 until there are no air bubbles in the pipeline; Close the second stop valve 18, the third stop valve 19, the fourth stop valve 20, and the fifth stop valve 21, open the first stop valve 17, turn on the air compressor 1 and the constant pressure pump 3, turn off the constant speed pump 9, and inject the oil sample in the oil storage tank 4 into the oil sample inlet of the microfluidic chip 6; S3. Calculate the preset length of the oil sample droplet in the microfluidic chip 6: Calculate the preset length of the oil sample droplet in the microfluidic chip 6 according to the preset length of the oil sample droplet in the capillary model 7; S4. Generate oil sample droplets: Close the second stop valve 18, the third stop valve 19, the fourth stop valve 20, and the fifth stop valve 21, and open the first stop valve 17; turn off the constant speed pump 9, turn on the air compressor 1 and the constant pressure pump 3, and inject the oil sample in the oil storage tank 4 into the observation channel until the preset length of the oil sample droplet in the microfluidic chip 6 is reached; Turn off the constant speed pump 9, close the first stop valve 17, the third stop valve 19, and the fifth stop valve 21; turn on the air compressor 1 and the constant pressure pump 3, open the second stop valve 18 and the fourth stop valve 20, and inject the formation water in the water storage tank 5 into the observation channel to truncate the oil sample droplet until the oil sample droplet enters the observation area of the industrial camera 12; S5. Aging of oil sample droplets: Turn off the air compressor 1 and the constant pressure pump 3, and let the oil sample droplet stand for aging until the pressure difference at both ends of the capillary model 7 is 0; S6: Displacement experiment: Select the constant pressure pump 2 for displacement or the constant speed pump 9 for displacement according to the actual situation until the oil sample droplet flows out from the drain port.

[0023] Specifically, the steps of cleaning the experimental device include: replacing the water storage tank 5 with an alcohol storage tank, and cleaning the microfluidic chip 6 and the capillary model 7 with alcohol.

[0024] The oil sample droplet in the capillary model is in a capsule shape, including a middle cylinder of the droplet and two hemispheres of the droplet. Therefore, in step S3, the preset length of the oil sample droplet in the microfluidic chip 6 is:

[0025] Among them, L chipThe preset length of the oil sample droplet in the microfluidic chip 6, μm; A is the diameter of the middle cylinder of the droplet, μm; B is the width of the oil sample droplet in the microfluidic chip 6, μm; C is the depth of the oil sample droplet in the microfluidic chip 6, μm; L total is the total length of the oil sample droplet in the capillary model 7, that is, the sum of the length of the middle cylinder of the droplet and the heights of 2 droplet hemispheres, μm; θ is the contact angle of the oil sample droplet in the capillary model 7.

[0026] The pressure value range of the oil channel is 20 - 200 mbr, and the pressure value range of the water channel is 70 - 200 mbr.

[0027] The flow rate range of the micro syringe in the constant speed pump 9 is 0.01 - 108 μL / min.

[0028] When the constant speed pump 9 is selected for displacement, In step S5, before aging the static oil sample droplet, close the first stop valve 17, the second stop valve 18, the fourth stop valve 20, and open the third stop valve 19, the fifth stop valve 21; In step S6, open the constant speed pump 9, and inject formation water through the micro syringe in the constant speed pump 9 for displacement.

[0029] When the constant pressure pump 3 is selected for displacement, In step S5, before aging the static oil sample droplet, close the first stop valve 17, the third stop valve 19, the fourth stop valve 20, and open the second stop valve 18, the fifth stop valve 21; In step S6, open the air compressor 1, the constant pressure pump 3, and displace through the formation water in the water storage tank 5.

[0030] Beneficial effects: The present invention can simulate the production dynamics of enhanced oil recovery by visualizing water - oil displacement at the pore scale. Aiming at the seepage characteristics of droplets in pores, it conducts research on single droplets under constant pressure or constant speed displacement, and observes the advancing law of the oil - water front, the migration morphology of droplets, and the change of channel pressure under different experimental variables, realizing the visualization of the water flooding process and residual oil, providing basic data for preliminarily understanding the oil - water seepage mechanism and understanding the utilization of residual oil during the water injection production process. Description of the Drawings

[0031] Figure 1 is an experimental device for simulating pore - scale water - oil visual displacement; Figure 2 is a schematic diagram of the microfluidic chip; Figure 3 is the influence of different oil sample droplet lengths and displacement speeds on the maximum migration pressure difference under constant speed conditions in Example 2; Figure 4Effect of different oil sample droplet lengths on the migration pressure difference under constant pressure conditions in Example 3.

[0032] Among them, 1 is an air compressor, 2 is a pressure gauge, 3 is a constant pressure pump, 4 is an oil storage tank, 5 is a water storage tank, 6 is a microfluidic chip, 7 is a capillary model, 8 is a first three-way joint, 9 is a constant speed pump, 10 is a first pressure sensor, 11 is a second pressure sensor, 12 is an industrial camera, 13 is a waste liquid pool, 14 is a four-way joint, 15 is a first one-way valve, 16 is a second one-way valve, 17 is a first stop valve, 18 is a second stop valve, 19 is a third stop valve, 20 is a fourth stop valve, 21 is a fifth stop valve, 22 is a computer, 23 is a planar light source, 24 is a second three-way joint; 601 is the water inlet of the microfluidic chip, 602 is the oil inlet of the microfluidic chip, and 603 is the liquid outlet of the microfluidic chip. Detailed implementation method

[0033] To further understand the content of the present invention, the present invention will be elaborated in detail below in combination with specific embodiments.

[0034] Among them, the microfluidic chip is purchased from Zhongxin Qiheng; the glass capillary is purchased from Pomex. The experimental temperature in the following examples is 20±2°C.

[0035] Example 1: This example provides an experimental device for simulating the visualization displacement of pore water-oil, as Figure 1 shown, including: a constant pressure pump channel and an observation channel; An air compressor 1 and a constant pressure pump 3 are sequentially arranged on the constant pressure pump channel; the constant pressure pump 3 has real-time response ability to ensure the precise establishment and cut-off of the system pressure instantaneously, so as to realize the controllability of the droplet length; A microfluidic chip 6, a capillary model 7, and a liquid discharge port are sequentially arranged on the observation channel; The constant pressure pump channel is connected to the observation channel through a water channel and an oil channel, and the water channel and the oil channel are connected in parallel.

[0036] A water storage tank 5 and a four-way joint 14 are sequentially arranged on the water channel; The four-way joint 14 is respectively connected to the water storage tank 5, the microfluidic chip 6, the constant speed pump 9, and the capillary model 7; An oil storage tank 4 is arranged on the oil channel.

[0037] A waste liquid pool 13 is also arranged below the liquid discharge port.

[0038] The microfluidic chip 6 includes a water inlet 601 of the microfluidic chip, an oil inlet 602 of the microfluidic chip, and a liquid outlet 603 of the microfluidic chip; The water inlet 601 and oil inlet 602 of the microfluidic chip are respectively connected to the water channel and oil channel; The liquid outlet 603 of the microfluidic chip is connected to the capillary model 7.

[0039] A micro syringe is arranged inside the constant speed pump 9.

[0040] A first pressure sensor 10 is arranged between the four-way joint 14 and the capillary model 7, and a second pressure sensor 11 is arranged between the capillary model 7 and the liquid discharge port, for monitoring the pressure change at both ends of the capillary model 7.

[0041] The first pressure sensor 10 is connected to the observation pipeline through the second three-way joint 24; The second pressure sensor 11 is connected to the observation pipeline through the first three-way joint 8.

[0042] A first one-way valve 15 and a first stop valve 17 are successively arranged between the oil storage tank 4 and the microfluidic chip 6; A second one-way valve 16 and a second stop valve 18 are successively arranged between the water storage tank 5 and the four-way joint 14; A third stop valve 19 is arranged between the constant speed pump 9 and the four-way joint 14; A fourth stop valve 20 is arranged between the four-way joint 14 and the microfluidic chip 6; A fifth stop valve 21 is arranged between the four-way joint 14 and the first pressure sensor 10.

[0043] Preferably, the microfluidic chip 6, the capillary model 7, and the waste liquid pool 13 are arranged on an optical flat plate for shockproof and height adjustment.

[0044] Preferably, an industrial camera 12 is arranged above the optical flat plate for capturing experimental images.

[0045] Preferably, a planar light source 23 is arranged beside the optical flat plate to provide light for the industrial camera 12; the industrial camera 12 controls the field of view of the industrial camera 12 through a sliding table to realize image acquisition of the microfluidic chip 6 and the capillary model 7.

[0046] The first pressure sensor 10, the second pressure sensor 11, and the industrial camera 12 are all connected to the computer 22 to realize data acquisition and storage.

[0047] Preferably, the microfluidic chip 6 and the second three-way joint 24 are connected by an L-shaped stainless steel needle.

[0048] Preferably, a pressure gauge 2 is arranged between the air compressor 1 and the constant pressure pump 3 to monitor the pressure provided by the air compressor 1.

[0049] The air compressor 1, pressure gauge 2, and constant pressure pump 3 are connected by a PU air tube with an inner diameter of 4 mm. The constant pressure pump 3 is connected to both the oil storage tank 4 and the water storage tank 5 by PU air tubes with an inner diameter of 4 mm.

[0050] The pipes of the oil channel and the water channel are both PTFE tubes with an inner diameter of 0.8 mm.

[0051] Further, in the microfluidic chip 6, the channel depth is 50 μm and the width is 250 μm.

[0052] In this embodiment, a single glass capillary is used as the capillary model, with an outer diameter of 200 μm and an inner diameter of 100 μm.

[0053] Embodiment 2: This embodiment uses the experimental device provided in Embodiment 1 to simulate the visual constant-speed displacement of pore water-oil. The specific steps are as follows: S1. Pretreatment: Clean the experimental device, connect the computer 22, adjust the industrial camera 12 and the light source, inject formation water into the water storage tank 5 and oil sample into the oil storage tank 4. S2. Remove air bubbles: Close the first stop valve 17, the third stop valve 19, and the fifth stop valve 21, open the second stop valve 18 and the fourth stop valve 20; close the constant speed pump 9, open the air compressor 1 and the constant pressure pump 3, and inject the formation water in the water storage tank 5 into the observation channel until formation water appears at the drain port. Close the first stop valve 17, the second stop valve 18, and the fourth stop valve 20, open the third stop valve 19 and the fifth stop valve 21; close the air compressor 1 and the constant pressure pump 3, open the constant speed pump 9, and inject formation water into the observation channel through the micro syringe of the constant speed pump 9 until there are no air bubbles in the pipeline. Close the second stop valve 18, the third stop valve 19, the fourth stop valve 20, and the fifth stop valve 21, open the first stop valve 17, open the air compressor 1 and the constant pressure pump 3, and close the constant speed pump 9, and inject the oil sample in the oil storage tank 4 into the oil sample inlet of the microfluidic chip 6. S3. Calculate the preset length of the oil sample droplet in the microfluidic chip 6: Calculate the preset length of the oil sample droplet in the microfluidic chip 6 based on the preset length of the oil sample droplet in the capillary model 7. S4. Generate oil sample droplets: Close the second stop valve 18, the third stop valve 19, the fourth stop valve 20, and the fifth stop valve 21, open the first stop valve 17; close the constant speed pump 9, open the air compressor 1 and the constant pressure pump 3, and inject the oil sample in the oil storage tank 4 into the observation channel until it reaches the preset length of the oil sample droplet in the microfluidic chip 6. Turn off the constant-speed pump 9, close the first check valve 17, the third check valve 19, and the fifth check valve 21; turn on the constant-pressure pump 3, open the second check valve 18 and the fourth check valve 20, and inject the formation water in the water storage tank 5 into the observation channel to cut off the oil sample droplets until the oil sample droplets enter the observation area of the industrial camera 12; S5. Aging of oil sample droplets: Turn off the constant-pressure pump 3, let the oil sample droplets stand for aging until the pressure difference at both ends of the capillary model 7 is 0; S6: Displacement experiment: Select the constant-pressure pump 2 or the constant-speed pump 9 for displacement according to the actual situation until the oil sample droplets flow out from the drain port.

[0054] Specifically, the steps of the cleaning experimental device include: replacing the water storage tank 5 with an alcohol storage tank, and cleaning the microfluidic chip 6 and the capillary model 7 with alcohol.

[0055] The oil sample droplets in the capillary model 7 are in a capsule shape, including a cylindrical middle part of the droplet and 2 hemispherical parts of the droplet. Therefore, in step S3, the preset length of the oil sample droplets in the microfluidic chip 6 is:

[0056] Where L chip is the preset length of the oil sample droplets in the microfluidic chip 6, μm; A is the diameter of the cylindrical middle part of the droplet, μm; B is the width of the oil sample droplets in the microfluidic chip 6, μm; C is the depth of the oil sample droplets in the microfluidic chip 6, μm; L total is the total length of the oil sample droplets in the capillary model 7, that is, the sum of the length of the cylindrical middle part of the droplet and the height of 2 hemispherical parts of the droplet, μm; θ is the contact angle of the oil sample droplets in the capillary model 7.

[0057] Where A = 100 μm, θ = 60°, B = 250 μm, C = 50 μm, L total = 800 μm; ; .

[0058] The pressure value of the oil channel is 200 mbr, and the pressure value of the water channel is 200 mbr.

[0059] In step S5, the aging time of the oil sample droplets is 4 h to simulate the aging process of petroleum in formation pores.

[0060] In step S5, before letting the oil sample droplets stand for aging, close the first check valve 17, the second check valve 18, and the fourth check valve 20, and open the third check valve 19 and the fifth check valve 21; In step S6, the constant-speed pump 9 is turned on, and formation water is injected through the micro syringe in the constant-speed pump 9 for displacement.

[0061] As Figure 3 shown, it is the influence of different oil sample droplet lengths and displacement speeds on the pressure difference during droplet migration. Among them, the abscissa is the oil sample droplet length, and the ordinate is the maximum pressure difference between the two ends of the glass capillary during the displacement process. In the laminar flow state, since the increase in flow velocity leads to an increase in the internal shear rate of the fluid, the viscous resistance linearly rises, so the viscous resistance increases linearly with the flow velocity.

[0062] Example 3: In this example, the experimental device provided in Example 1 is used to simulate the pore water-oil visual constant-pressure displacement. The specific experimental process is the same as that in Example 2, except that in step S5, before standing the oil sample droplet for aging, the first stop valve 17, the third stop valve 19, and the fourth stop valve 20 are closed, and the second stop valve 18 and the fifth stop valve 21 are opened; in step S6, the air compressor 1 and the constant-pressure pump 3 are turned on, and displacement is carried out with the formation water in the water storage tank 5.

[0063] As Figure 4 shown, it is the influence of different oil sample droplet lengths on the pressure difference during droplet migration. The change of the pressure difference at both ends of the capillary model 7 with the migration time is studied when the oil sample droplet lengths are 2.23, 3.69, 4.08, and 6.34 mm. When the oil sample droplet is stationary, the Laplace pressures at both ends of the two curved liquid surfaces are equal and balanced with the static contact angle of the capillary inner wall. At this time, the pressure difference at both ends is 0. During the process of the oil sample droplet moving from stationary to moving, it needs to overcome the resistance of contact angle hysteresis and the dynamic change of the curvature of the oil sample droplet curved liquid surface, resulting in fluctuations in the pressure difference curve; when the oil sample droplet is longer, the longer the liquid column needs to be displaced, the greater the distance and area of the viscous force, resulting in a linear increase in resistance and thus a greater pressure difference.

[0064] The working principle of the constant-pressure pump is to feedback and adjust the output through the built-in pressure sensor, and there is a response time. Different acting forces will be generated during the displacement process due to different migration states of the oil sample droplet, and its response time just reflects this phenomenon, so it is fluctuating. When the migration state of the oil sample droplet is stable, its pressure value is also stable.

Claims

1. An experimental device for visual displacement of water-oil in pore-level microchannels, characterized in that, Including: A constant-pressure pump channel and an observation channel; An air compressor (1) and a constant-pressure pump (3) are successively arranged on the constant-pressure pump channel; a microfluidic chip (6), a capillary model (7), and a liquid discharge port are successively arranged on the observation channel; the constant-pressure pump channel is connected to the observation channel through a water channel and an oil channel, and the water channel and the oil channel are connected in parallel; A water storage tank (5) and a four-way joint (14) are successively arranged on the water channel; the four-way joint (14) is respectively connected to the water storage tank (5), the microfluidic chip (6), a constant-speed pump (9), and the capillary model (7); an oil storage tank (4) is arranged on the oil channel; A first pressure sensor (10) is arranged between the four-way joint (14) and the capillary model (7), and a second pressure sensor (11) is arranged between the capillary model (7) and the liquid discharge port; A first one-way valve (15) and a first stop valve (17) are successively arranged between the oil storage tank (4) and the microfluidic chip (6); a second one-way valve (16) and a second stop valve (18) are successively arranged between the water storage tank (5) and the four-way joint (14); a third stop valve (19) is arranged between the constant-speed pump (9) and the four-way joint (14); a fourth stop valve (20) is arranged between the four-way joint (14) and the microfluidic chip (6); a fifth stop valve (21) is arranged between the four-way joint (14) and the first pressure sensor (10); The experimental device for water-oil visual displacement in the pore-level microchannel further includes an industrial camera (12) for realizing image acquisition of the microfluidic chip (6) and the capillary model (7).

2. The experimental device according to claim 1, wherein A waste liquid pool (13) is further arranged below the liquid discharge port; A micro syringe is arranged inside the constant-speed pump (9).

3. The experimental device according to claim 1, wherein The microfluidic chip (6) includes a microfluidic chip water inlet (601), a microfluidic chip oil inlet (602), and a microfluidic chip liquid outlet (603); The microfluidic chip water inlet (601) and the microfluidic chip oil inlet (602) are respectively connected to the water channel and the oil channel; The microfluidic chip liquid outlet (603) is connected to the capillary model (7).

4. The experimental device according to claim 2, wherein The microfluidic chip (6), the capillary model (7), and the waste liquid pool (13) are arranged on an optical flat plate; A plane light source (23) is arranged beside the optical flat plate to provide light for the industrial camera (12); The industrial camera (12) controls the field of view of the industrial camera (12) through a sliding table; The first pressure sensor (10), the second pressure sensor (11), and the industrial camera (12) are all connected to a computer (22); A pressure gauge (2) is arranged between the air compressor (1) and the constant-pressure pump (3).

5. The experimental device according to claim 1, wherein The first pressure sensor (10) is connected to an observation pipeline through a second three-way joint (24), and the second pressure sensor (11) is connected to the observation pipeline through a first three-way joint (8); The microfluidic chip (6) is connected to the second three-way joint (24) by an L-shaped stainless steel needle.

6. The experimental device according to claim 1, wherein The capillary model (7) can be set as a single glass capillary or two or more capillaries in parallel.

7. An experimental method for water-oil visualization displacement using the experimental device according to any one of claims 1-6, comprising: S1. Pretreatment: Clean the experimental device, connect the computer (22), adjust the industrial camera (12), inject formation water into the water storage tank (5), and inject oil samples into the oil storage tank (4); S2. Remove air bubbles: Close the first stop valve (17), the third stop valve (19), and the fifth stop valve (21), and open the second stop valve (18) and the fourth stop valve (20); turn off the constant speed pump (9), turn on the air compressor (1) and the constant pressure pump (3), and inject the formation water in the water storage tank (5) into the observation channel until formation water appears at the drainage port; Close the first stop valve (17), the second stop valve (18), and the fourth stop valve (20), and open the third stop valve (19) and the fifth stop valve (21); turn off the air compressor (1) and the constant pressure pump (3), turn on the constant speed pump (9), and inject formation water into the observation channel through the constant speed pump (9) until there are no air bubbles in the pipeline; Close the second stop valve (18), the third stop valve (19), the fourth stop valve (20), and the fifth stop valve (21), open the first stop valve (17), turn on the air compressor (1), the constant pressure pump (3), and turn off the constant speed pump (9), and inject the oil sample in the oil storage tank (4) into the oil sample inlet of the microfluidic chip (6); S3. Calculate the preset length of the oil sample droplet in the microfluidic chip (6): Calculate the preset length of the oil sample droplet in the microfluidic chip (6) according to the preset length of the oil sample droplet in the capillary model (7); S4. Generate oil sample droplets: Close the second stop valve (18), the third stop valve (19), the fourth stop valve (20), and the fifth stop valve (21), and open the first stop valve (17); turn off the constant speed pump (9), turn on the air compressor (1) and the constant pressure pump (3), and inject the oil sample in the oil storage tank (4) into the observation channel until the preset length of the oil sample droplet in the microfluidic chip (6) is reached; Turn off the constant speed pump (9), close the first stop valve (17), the third stop valve (19), and the fifth stop valve (21); turn on the air compressor (1) and the constant pressure pump (3), open the second stop valve (18) and the fourth stop valve (20), and inject the formation water in the water storage tank (5) into the observation channel to truncate the oil sample droplet until the oil sample droplet enters the observation area of the industrial camera (12); S5. Aging of oil sample droplets: Turn off the air compressor (1) and the constant pressure pump (3), and let the oil sample droplets stand for aging until the pressure difference at both ends of the capillary model (7) is 0; S6: Displacement experiment: Select displacement by the constant pressure pump (2) or the constant speed pump (9) according to the actual situation until the oil sample droplet flows out from the drainage port.

8. The experimental method according to claim 7, wherein In the capillary model (7), the oil sample droplets are in a capsule shape, including a middle cylinder of the droplet and two hemispheres of the droplet. Therefore, in step S3, the preset length of the oil sample droplets in the microfluidic chip (6) is as follows: Among them, L chip is the preset length of the oil sample droplet in the microfluidic chip (6), in μm; A is the diameter of the middle cylinder of the droplet, in μm; B is the width of the oil sample droplet in the microfluidic chip (6), in μm; C is the depth of the oil sample droplet in the microfluidic chip (6), in μm; L total is the total length of the oil sample droplet in the capillary model (7), that is, the sum of the length of the middle cylinder of the droplet and the heights of 2 droplet hemispheres, in μm; θ is the contact angle of the oil sample droplet in the capillary model (7).

9. The experimental method according to claim 7, wherein when a constant-speed pump (9) is selected for displacement, in step S5, before the oil sample droplets are allowed to stand for aging, the first stop valve (17), the second stop valve (18), and the fourth stop valve (20) are closed, and the third stop valve (19) and the fifth stop valve (21) are opened; in step S6, the constant-speed pump (9) is turned on, and formation water is injected through the constant-speed pump (9) for displacement; when a constant-pressure pump (3) is selected for displacement, in step S5, before the oil sample droplets are allowed to stand for aging, the first stop valve (17), the third stop valve (19), and the fourth stop valve (20) are closed, and the second stop valve (18) and the fifth stop valve (21) are opened; in step S6, the air compressor (1) and the constant-pressure pump (3) are turned on, and displacement is performed with the formation water in the water storage tank (5).

10. The experimental method according to claim 7, wherein the pressure value range of the oil channel is 20 - 200 mbr, and the pressure value range of the water channel is 70 - 200 mbr.

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