An experimental apparatus and method for visualizing water-oil displacement in pore-scale microchannels

Abstract

This invention belongs to the field of oil reservoir development technology, specifically relating to an experimental device and method for visualizing water-oil displacement in pore-level microchannels. By setting up a microfluidic chip to generate single droplets and controlling the droplet length, and by setting up different capillary models to simulate cores with different pore sizes, the invention enables visual observation of the oil-water front advancement law and droplet transport morphology during the displacement process, providing key data support for studying the microscopic seepage mechanism in oil reservoir development.

Description

Technical Field

[0001] This invention belongs to the field of oil reservoir development technology, specifically relating to an experimental device and method for visual water-oil displacement in pore-level microchannels. Background Technology

[0002] Conventional oil and gas reservoirs have experienced sluggish production growth in recent years, entering a phase of "high proven reserves, low production growth." Reservoirs are essentially porous media used for storing and extracting hydrocarbons; water is also present, leading to multiphase flow of oil and water. After drilling, oil initially flows to the surface due to the reservoir's natural energy. Subsequently, energy replenishment is needed to maintain the pressure gradient, during which time significant fluid intrusion may occur, resulting in severe water flooding within the well. This causes the continuous oil phase in the pores to transform into a discontinuous oil phase, which remains as residual oil in the pores, reducing oil washing efficiency and thus affecting recovery efficiency. Currently, most research on oil-water migration mechanisms in porous media focuses on deformation phenomena during fluid migration under different conditions, generally using numerical simulations. However, few studies have explored the microscopic mechanisms of fluid migration under different displacement conditions through physical simulations, examining the physicochemical properties of the channels and the fluid itself.

[0003] Chinese patent CN105422079A discloses a dynamic visualization observation device for displacement experiments. This device observes the dynamic migration of oil and water in different reservoir types using different core sections, and monitors the dynamic migration of oil and water during displacement under different injection systems. It can also observe the distribution of residual oil and remaining oil after displacement, allowing for targeted development of reservoir exploitation and enhanced oil recovery strategies. While this dynamic visualization observation device can observe oil and water migration patterns and distribution in real time, it cannot study the flow characteristics of single droplets in pores. Furthermore, the raw material for the visualization micro-model is polydimethylsiloxane, which is hydrophobic, and therefore usually requires surface hydrophilication treatment during fabrication to enhance the interfacial properties with the fluid. More importantly, a circular cross-section is crucial for studying the flow characteristics of single droplets in microchannels, but the visualization micro-model in this patent cannot fabricate a circular cross-section for the microchannel, thus preventing the study of single oil droplet migration phenomena in circular cross-section microchannels. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides an experimental apparatus and method for visualizing water-oil displacement within a pore-level microchannel. By using a microfluidic chip to generate single droplets and controlling their length, and by setting up different capillary models to simulate core samples with varying pore sizes, the invention enables visual observation of the oil-water front propagation patterns and droplet transport morphology during the displacement process.

[0005] An experimental apparatus for visualizing water-oil displacement within pore-scale microchannels, comprising:

[0006] Constant pressure pump channel, observation channel;

[0007] An air compressor 1 and a constant pressure pump 3 are sequentially installed on the constant pressure pump channel; the constant pressure pump 3 has real-time response capability to ensure that the system pressure is accurately established and cut off in an instant, so as to achieve controllable droplet length.

[0008] The observation channel is sequentially equipped with a microfluidic chip 6, a capillary model 7, and a drain outlet.

[0009] 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.

[0010] A water storage tank 5 and a four-way connector 14 are sequentially installed on the water channel;

[0011] The four-way connector 14 is connected to the water storage tank 5, the microfluidic chip 6, the constant speed pump 9, and the capillary model 7 respectively.

[0012] An oil storage tank 4 is installed on the oil channel.

[0013] Preferably, a waste liquid tank 13 is also provided below the drain outlet.

[0014] 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;

[0015] The microfluidic chip water inlet 601 and microfluidic chip oil inlet 602 are respectively connected to the water channel and the oil channel;

[0016] The microfluidic chip outlet 603 is connected to the capillary model 7.

[0017] Preferably, a micro-injector is installed inside the constant speed pump 9.

[0018] Preferably, a first pressure sensor 10 is provided between the four-way connector 14 and the capillary model 7, and a second pressure sensor 11 is provided between the capillary model 7 and the drain port, for monitoring pressure changes at both ends of the capillary model 7.

[0019] Preferably, the first pressure sensor 10 is connected to the observation pipeline via the second tee connector 24;

[0020] Preferably, the second pressure sensor 11 is connected to the observation pipeline via the first tee connector 8.

[0021] Preferably, a first one-way valve 15 and a first check valve 17 are sequentially provided between the oil storage tank 4 and the microfluidic chip 6;

[0022] A second one-way valve 16 and a second check valve 18 are sequentially installed between the water storage tank 5 and the four-way connector 14.

[0023] A third check valve 19 is provided between the constant speed pump 9 and the four-way connector 14;

[0024] A fourth check valve 20 is provided between the four-way connector 14 and the microfluidic chip 6;

[0025] A fifth check valve 21 is provided between the four-way connector 14 and the first pressure sensor 10.

[0026] Preferably, the microfluidic chip 6, capillary model 7, and waste liquid pool 13 are mounted on an optical flat plate for shock absorption and height adjustment.

[0027] Preferably, an industrial camera 12 is mounted above the optical flat plate to capture experimental images.

[0028] Preferably, a planar light source 23 is provided next to the optical flat plate to provide a light source for the industrial camera 12; the industrial camera 12 controls the field of view of the industrial camera 12 through a slide table to realize image acquisition of the microfluidic chip 6 and the capillary model 7.

[0029] 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.

[0030] Preferably, the microfluidic chip 6 is connected to the second tee connector 24 via an L-shaped stainless steel pin.

[0031] Preferably, a pressure gauge 2 is installed between the air compressor 1 and the constant pressure pump 3 to monitor the pressure provided by the air compressor 1.

[0032] Preferably, the air compressor 1, pressure gauge 2, and constant pressure pump 3 are connected by PU air pipes, and the constant pressure pump 3 is connected to the oil storage tank 4 and the water storage tank 5 by PU air pipes; more preferably, the inner diameter of the PU air pipe is 4mm.

[0033] Preferably, the oil channel and water channel are both PTFE pipes; more preferably, the inner diameter of the PTFE pipe is 0.8 mm.

[0034] The capillary model 7 can be set as a single glass capillary or two or more capillary tubes connected in parallel to achieve realistic simulation of core samples from strata under different conditions.

[0035] Furthermore, the present invention also provides an experimental method for visually displacing water-oil using the above-described experimental apparatus, comprising:

[0036] S1. Preprocessing:

[0037] Clean the experimental setup, connect the computer 22, adjust the industrial camera 12 and the light source, and inject formation water into the water storage tank 5 and oil sample into the oil storage tank 4.

[0038] S2, Expel air bubbles:

[0039] 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; 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 drain outlet.

[0040] Close the first check valve 17, the second check valve 18, and the fourth check valve 20; open the third check valve 19 and the fifth check valve 21; turn off the air compressor 1 and the constant pressure pump 3; turn on the constant speed pump 9; inject formation water into the observation channel through the micro-injector of the constant speed pump 9 until there are no air bubbles in the pipeline.

[0041] Close the second check valve 18, the third check valve 19, the fourth check valve 20, and the fifth check valve 21; open the first check 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 from the oil storage tank 4 into the oil sample inlet of the microfluidic chip 6.

[0042] S3. Calculate the preset length of the oil droplet inside the microfluidic chip 6:

[0043] The preset length of the oil sample droplet in the microfluidic chip 6 is calculated based on the preset length of the oil sample droplet in the capillary model 7.

[0044] S4. Generate oil droplets:

[0045] 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, and turn on the air compressor 1 and the constant pressure pump 3 to 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.

[0046] Turn off constant speed pump 9, and close first stop valve 17, third stop valve 19, and fifth stop valve 21; turn on air compressor 1 and constant pressure pump 3, and open second stop valve 18 and fourth stop valve 20 to inject formation water from water storage tank 5 into the observation channel to cut off oil sample droplets until the oil sample droplets enter the observation area of ​​industrial camera 12.

[0047] S5. Aging of oil droplets:

[0048] Turn off air compressor 1 and constant pressure pump 3, and let the oil sample droplets stand for aging until the pressure difference across capillary model 7 is 0.

[0049] S6: Displacement Experiment

[0050] Choose either constant pressure pump 2 or constant speed pump 9 for displacement based on the actual situation until the oil sample droplets flow out from the drain port.

[0051] 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.

[0052] In the capillary model, the oil droplet is capsule-shaped, comprising a central cylinder and two hemispheres. Therefore, in step S3, the preset length of the oil droplet within the microfluidic chip 6 is:

[0053]

[0054] Among them, L chip The preset length of the oil droplet in the microfluidic chip 6 is μm; A is the diameter of the central cylinder of the droplet, μm; B is the width of the oil droplet in the microfluidic chip 6, μm; C is the depth of the oil droplet in the microfluidic chip 6, μm; L total θ is the total length of the oil sample droplet in capillary model 7, which is the sum of the length of the central cylinder of the droplet and the height of the two droplet hemispheres, in μm; θ is the contact angle of the oil sample droplet in capillary model 7.

[0055] The oil channel pressure range is 20~200 mbar, and the water channel pressure range is 70~200 mbar.

[0056] The flow rate of the micro-injector in the constant speed pump 9 is 0.01~108μL / min.

[0057] When selecting constant speed pump 9 for displacement

[0058] In step S5, before the oil sample droplets are allowed to stand for aging, the first check valve 17, the second check valve 18, and the fourth check valve 20 are closed, and the third check valve 19 and the fifth check valve 21 are opened.

[0059] In step S6, the constant speed pump 9 is turned on, and formation water is injected through the micro-injector inside the constant speed pump 9 for displacement.

[0060] When selecting constant pressure pump 3 drive replacement

[0061] In step S5, before the oil sample droplets are allowed to stand for aging, the first check valve 17, the third check valve 19, and the fourth check valve 20 are closed, and the second check valve 18 and the fifth check valve 21 are opened.

[0062] In step S6, the air compressor 1 and constant pressure pump 3 are turned on, and the formation water in the water storage tank 5 is used for displacement.

[0063] Beneficial effects:

[0064] This invention can simulate the dynamic generation of enhanced oil recovery through visualized water-oil displacement at the pore level. It studies the seepage characteristics of droplets in pores under constant pressure or constant velocity displacement of single droplets, and observes the advance law of the oil-water front, droplet migration morphology, and channel pressure changes under different experimental variables during the displacement process. It realizes the visualization of the water drive process and residual oil, providing basic data for a preliminary understanding of the oil-water seepage mechanism and understanding the utilization of residual oil during water injection. Attached Figure Description

[0065] Figure 1 An experimental setup for simulating visual displacement of pore water-oil;

[0066] Figure 2 This is a schematic diagram of a microfluidic chip;

[0067] Figure 3 This illustrates the effect of different oil droplet lengths and displacement velocities on the maximum transport pressure difference under constant-rate conditions in Example 2.

[0068] Figure 4 This illustrates the effect of different oil droplet lengths on the transport pressure difference under constant pressure conditions in Example 3.

[0069] 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 connector, 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 connector, 15 is a first check valve, 16 is a second check valve, 17 is a first check valve, 18 is a second check valve, 19 is a third check valve, 20 is a fourth check valve, 21 is a fifth check valve, 22 is a computer, 23 is a planar light source, and 24 is a second three-way connector.

[0070] 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

[0071] To further understand the content of this invention, the invention will be described in detail below with reference to specific embodiments.

[0072] The microfluidic chip was purchased from SMIC; the glass capillary was purchased from Pomex. The experimental temperature for all the following embodiments was 20±2℃.

[0073] Example 1:

[0074] This embodiment provides an experimental apparatus for simulating visual displacement of pore water-oil, such as... Figure 1 As shown, it includes: constant pressure pump channel and observation channel;

[0075] An air compressor 1 and a constant pressure pump 3 are sequentially installed on the constant pressure pump channel; the constant pressure pump 3 has real-time response capability to ensure that the system pressure is accurately established and cut off in an instant, so as to achieve controllable droplet length.

[0076] The observation channel is sequentially equipped with a microfluidic chip 6, a capillary model 7, and a drain outlet.

[0077] 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.

[0078] A water storage tank 5 and a four-way connector 14 are sequentially installed on the water channel;

[0079] The four-way connector 14 is connected to the water storage tank 5, the microfluidic chip 6, the constant speed pump 9, and the capillary model 7 respectively.

[0080] An oil storage tank 4 is installed on the oil channel.

[0081] A waste liquid pool 13 is also provided below the drain outlet.

[0082] The microfluidic chip 6 includes a microfluidic chip water inlet 601, a microfluidic chip oil inlet 602, and a microfluidic chip liquid outlet 603;

[0083] The microfluidic chip water inlet 601 and microfluidic chip oil inlet 602 are respectively connected to the water channel and the oil channel;

[0084] The microfluidic chip outlet 603 is connected to the capillary model 7.

[0085] The constant speed pump 9 is equipped with a micro-injector.

[0086] A first pressure sensor 10 is installed between the four-way connector 14 and the capillary model 7, and a second pressure sensor 11 is installed between the capillary model 7 and the drain port, for monitoring pressure changes at both ends of the capillary model 7.

[0087] The first pressure sensor 10 is connected to the observation pipeline via the second tee connector 24;

[0088] The second pressure sensor 11 is connected to the observation pipeline via the first tee connector 8.

[0089] A first one-way valve 15 and a first check valve 17 are sequentially arranged between the oil storage tank 4 and the microfluidic chip 6;

[0090] A second one-way valve 16 and a second check valve 18 are sequentially installed between the water storage tank 5 and the four-way connector 14.

[0091] A third check valve 19 is provided between the constant speed pump 9 and the four-way connector 14;

[0092] A fourth check valve 20 is provided between the four-way connector 14 and the microfluidic chip 6;

[0093] A fifth check valve 21 is provided between the four-way connector 14 and the first pressure sensor 10.

[0094] Preferably, the microfluidic chip 6, capillary model 7, and waste liquid pool 13 are mounted on an optical flat plate for shock absorption and height adjustment.

[0095] Preferably, an industrial camera 12 is mounted above the optical flat plate to capture experimental images.

[0096] Preferably, a planar light source 23 is provided next to the optical flat plate to provide a light source for the industrial camera 12; the industrial camera 12 controls the field of view of the industrial camera 12 through a slide table to realize image acquisition of the microfluidic chip 6 and the capillary model 7.

[0097] 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.

[0098] Preferably, the microfluidic chip 6 is connected to the second tee connector 24 via an L-shaped stainless steel pin.

[0099] Preferably, a pressure gauge 2 is installed between the air compressor 1 and the constant pressure pump 3 to monitor the pressure provided by the air compressor 1.

[0100] The air compressor 1, pressure gauge 2, and constant pressure pump 3 are connected by PU air pipes with an inner diameter of 4mm. The constant pressure pump 3 is also connected to the oil storage tank 4 and the water storage tank 5 by PU air pipes with an inner diameter of 4mm.

[0101] The oil and water channels are both made of PTFE with an inner diameter of 0.8 mm.

[0102] Furthermore, in the microfluidic chip 6, the channel depth is 50μm and the width is 250μm.

[0103] 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.

[0104] Example 2:

[0105] This embodiment uses the experimental setup provided in Example 1 to simulate the visualized constant-rate displacement of pore water-oil. The specific steps are as follows:

[0106] S1. Preprocessing:

[0107] Clean the experimental setup, connect the computer 22, adjust the industrial camera 12 and the light source, and inject formation water into the water storage tank 5 and oil sample into the oil storage tank 4.

[0108] S2, Expel air bubbles:

[0109] 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; 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 drain outlet.

[0110] Close the first check valve 17, the second check valve 18, and the fourth check valve 20; open the third check valve 19 and the fifth check valve 21; turn off the air compressor 1 and the constant pressure pump 3; turn on the constant speed pump 9; inject formation water into the observation channel through the micro-injector of the constant speed pump 9 until there are no air bubbles in the pipeline.

[0111] Close the second check valve 18, the third check valve 19, the fourth check valve 20, and the fifth check valve 21; open the first check 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 from the oil storage tank 4 into the oil sample inlet of the microfluidic chip 6.

[0112] S3. Calculate the preset length of the oil droplet inside the microfluidic chip 6:

[0113] The preset length of the oil sample droplet in the microfluidic chip 6 is calculated based on the preset length of the oil sample droplet in the capillary model 7.

[0114] S4. Generate oil droplets:

[0115] 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, and turn on the air compressor 1 and the constant pressure pump 3 to 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.

[0116] Turn off constant speed pump 9, and close first stop valve 17, third stop valve 19, and fifth stop valve 21; turn on constant pressure pump 3, and open second stop valve 18 and fourth stop valve 20 to inject formation water from water storage tank 5 into the observation channel to cut off oil sample droplets until the oil sample droplets enter the observation area of ​​industrial camera 12.

[0117] S5. Aging of oil droplets:

[0118] Turn off the constant pressure pump 3 and let the oil sample droplet stand for aging until the pressure difference across the capillary model 7 is 0.

[0119] S6: Displacement Experiment

[0120] Choose either constant pressure pump 2 or constant speed pump 9 for displacement based on the actual situation until the oil sample droplets flow out from the drain port.

[0121] 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.

[0122] In the capillary model 7, the oil droplet is capsule-shaped, comprising a central cylinder and two hemispheres. Therefore, in step S3, the preset length of the oil droplet within the microfluidic chip 6 is:

[0123]

[0124] Among them, L chip The preset length of the oil droplet in the microfluidic chip 6 is μm; A is the diameter of the central cylinder of the droplet, μm; B is the width of the oil droplet in the microfluidic chip 6, μm; C is the depth of the oil droplet in the microfluidic chip 6, μm; L total θ is the total length of the oil sample droplet in capillary model 7, which is the sum of the length of the central cylinder of the droplet and the height of the two droplet hemispheres, in μm; θ is the contact angle of the oil sample droplet in capillary model 7.

[0125] Among them, A=100μm, θ=60°, B=250μm, C=50μm, L total =800μm;

[0126] ;

[0127] .

[0128] The oil channel pressure is 200 mbar, and the water channel pressure is 200 mbar.

[0129] In step S5, the oil sample droplet is aged for 4 hours to simulate the aging process of oil in formation pores.

[0130] In step S5, before the oil sample droplets are allowed to stand for aging, the first check valve 17, the second check valve 18, and the fourth check valve 20 are closed, and the third check valve 19 and the fifth check valve 21 are opened.

[0131] In step S6, the constant speed pump 9 is turned on, and formation water is injected through the micro-injector inside the constant speed pump 9 for displacement.

[0132] like Figure 3The figure shows the effect of different oil droplet lengths and displacement velocities on the pressure difference during droplet transport. The horizontal axis represents the oil droplet length, and the vertical axis represents the maximum pressure difference across the glass capillary during displacement. In laminar flow, the increased flow velocity leads to an increased internal shear rate, resulting in a linear increase in viscous drag. Therefore, viscous drag increases linearly with flow velocity.

[0133] Example 3:

[0134] This embodiment uses the experimental setup provided in Example 1 to simulate the visualized constant-pressure displacement of pore water-oil. The specific experimental procedure is the same as in Example 2, except that...

[0135] In step S5, before the oil sample droplets are allowed to stand for aging, the first check valve 17, the third check valve 19, and the fourth check valve 20 are closed, and the second check valve 18 and the fifth check valve 21 are opened.

[0136] In step S6, the air compressor 1 and constant pressure pump 3 are turned on, and the formation water in the water storage tank 5 is used for displacement.

[0137] like Figure 4 The figure shows the effect of different oil droplet lengths on the pressure difference during droplet migration. The pressure difference across capillary model 7 was studied with migration time when the oil droplet lengths were 2.23, 3.69, 4.08, and 6.34 mm. When the oil droplet is stationary, the Laplace pressures of the two menisci are equal and balanced with the static contact angle with the inner wall of the capillary, resulting in a zero pressure difference. During the process from stationary to migration, the oil droplet needs to overcome the resistance of contact angle hysteresis and the dynamic changes in the curvature of the menisci, causing fluctuations in the pressure difference curve. The longer the oil droplet, the longer the liquid column that needs to be displaced, resulting in a larger distance and area of ​​viscous force, leading to a linear increase in resistance and thus a larger pressure difference.

[0138] The constant pressure pump works by adjusting the output through feedback from the built-in pressure sensor. There is a response time. During the displacement process, different states of oil droplet movement will generate different forces. The response time reflects this phenomenon and is therefore fluctuating. When the state of oil droplet movement is stable, the pressure value is also stable.

Claims

1. An experimental apparatus for visually displacing water and oil in porous microchannels, characterized in that, include: Constant pressure pump channel, observation channel; An air compressor (1) and a constant pressure pump (3) are sequentially arranged on the constant pressure pump channel; a microfluidic chip (6), a capillary model (7), and a drain 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. A water storage tank (5) and a four-way connector (14) are sequentially arranged on the water channel; the four-way connector (14) is connected to the water storage tank (5), the microfluidic chip (6), the constant speed pump (9), and the capillary model (7) respectively; an oil storage tank (4) is arranged on the oil channel. A first pressure sensor (10) is provided between the four-way connector (14) and the capillary model (7), and a second pressure sensor (11) is provided between the capillary model (7) and the drain port. A first check valve (15) and a first check valve (17) are sequentially arranged between the oil storage tank (4) and the microfluidic chip (6); a second check valve (16) and a second check valve (18) are sequentially arranged between the water storage tank (5) and the four-way connector (14); a third check valve (19) is arranged between the constant speed pump (9) and the four-way connector (14); a fourth check valve (20) is arranged between the four-way connector (14) and the microfluidic chip (6); and a fifth check valve (21) is arranged between the four-way connector (14) and the first pressure sensor (10). The experimental device for visualizing water-oil displacement in the pore-level microchannel also includes an industrial camera (12) for image acquisition of the microfluidic chip (6) and the capillary model (7). The microfluidic chip (6) includes a water inlet (601), an oil inlet (602), and a liquid outlet (603). The microfluidic chip water inlet (601) and microfluidic chip oil inlet (602) are respectively connected to the water channel and the oil channel; The microfluidic chip outlet (603) is connected to the capillary model (7).

2. The experimental apparatus according to claim 1, characterized in that, A waste liquid pool (13) is also provided below the drain outlet; A micro-injector is installed inside the constant speed pump (9).

3. The experimental apparatus according to claim 2, characterized in that, The microfluidic chip (6), capillary model (7), and waste liquid pool (13) are mounted on an optical flat plate; A planar light source (23) is placed next to the optical flat plate to provide a light source for the industrial camera (12); The industrial camera (12) controls the field of view of the industrial camera (12) through a slide table; The first pressure sensor (10), the second pressure sensor (11), and the industrial camera (12) are all connected to the computer (22); A pressure gauge (2) is installed between the air compressor (1) and the constant pressure pump (3).

4. The experimental apparatus according to claim 1, characterized in that, The first pressure sensor (10) is connected to the observation pipeline between the microfluidic chip (6) and the capillary model (7) through the second tee connector (24), and the second pressure sensor (11) is connected to the observation pipeline between the capillary model (7) and the drain port through the first tee connector (8). The microfluidic chip (6) is connected to the second tee connector (24) via an L-shaped stainless steel pin.

5. The experimental apparatus according to claim 1, characterized in that, The capillary model (7) can be set as a single glass capillary or two or more capillary tubes connected in parallel.

6. An experimental method for visually displacing water-oil using the experimental apparatus described in any one of claims 1-5, comprising: S1. Preprocessing: Clean the experimental setup, 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, Expel 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); close the constant speed pump (9), and open the air compressor (1) and the constant pressure pump (3) to inject the formation water in the water storage tank (5) into the observation channel until formation water appears at the drain outlet; 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), and turn on the constant speed pump (9). 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 check valve (18), the third check valve (19), the fourth check valve (20), and the fifth check valve (21), open the first check 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 droplet inside the microfluidic chip (6): The preset length of the oil sample droplet in the microfluidic chip (6) is calculated based on the preset length of the oil sample droplet in the capillary model (7); S4. Generate oil 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), and 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), and open the second stop valve (18) and the fourth stop valve (20) to 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 droplets: Turn off the air compressor (1) and constant pressure pump (3), and let the oil sample droplets stand for aging until the pressure difference between the two ends of the capillary model (7) is 0; S6: Displacement Experiment Choose a constant pressure pump (3) or a constant speed pump (9) to displace the oil sample until the oil droplets flow out of the drain port.

7. The experimental method according to claim 6, characterized in that, In the capillary model (7), the oil droplet is capsule-shaped, including a central cylinder and two droplet hemispheres. Therefore, in step S3, the preset length of the oil droplet in the microfluidic chip (6) is: Among them, L chip The preset length of the oil droplet in the microfluidic chip (6) is μm; A is the diameter of the central cylinder of the droplet, μm; B is the width of the oil droplet in the microfluidic chip (6), μm; C is the depth of the oil droplet in the microfluidic chip (6), μm; L total θ is the total length of the oil sample droplet in the capillary model (7), which is the sum of the length of the central cylinder of the droplet and the height of the two droplet hemispheres, in μm; θ is the contact angle of the oil sample droplet in the capillary model (7).

8. The experimental method according to claim 6, characterized in that, 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 check valve (17), the second check valve (18), and the fourth check valve (20) are closed, and the third check valve (19) and the fifth check 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 check valve (17), the third check valve (19), and the fourth check valve (20) are closed, and the second check valve (18) and the fifth check valve (21) are opened. In step S6, the air compressor (1) and constant pressure pump (3) are turned on to displace the formation water in the water storage tank (5).

9. The experimental method according to claim 6, characterized in that, The oil channel pressure range is 20~200 mbar, and the water channel pressure range is 70~200 mbar.

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