Visualizing experiment device and method for porous medium displacement under different gravities

Abstract

The application discloses a kind of visualization test device and method of porous medium displacement under different gravity.The microfluidic chip model module, displacement injection module, image acquisition module and light source module are placed in model box shell, the model box shell is placed in the basket of centrifuge, fluid is stored in displacement injection module, for providing fluid for microfluidic chip model module, displacement injection module is connected with microfluidic chip model module, image acquisition module is used to collect optical image information of microfluidic chip model module in fluid displacement process;Method includes dyeing original fluid, installing microfluidic chip, using injection pump to push plastic syringe to inject fluid into microfluidic chip, and observing the flow migration mode and fluid distribution of fluid displacement process in porous medium.The device of the application is simple and easy to manufacture, easy to operate, and has high stability, uses supergravity and microgravity for model test, realizes real-time observation on two-phase fluid displacement process.

Description

Technical Field

[0001] This invention belongs to the field of porous media fluid displacement model experiments, specifically involving a visualization experimental device and method for porous media displacement under different gravity conditions. Background Technology

[0002] In recent years, with the construction of major energy projects such as underground carbon dioxide geological sequestration and underground hydrogen storage, the long-term displacement process of fluids in pores under the influence of gravity has attracted widespread attention. Taking carbon dioxide geological sequestration as an example, when carbon dioxide is injected 1 kilometer underground, the buoyancy caused by the density difference leads to the upward migration of carbon dioxide. This process is affected by brine and rock. Therefore, understanding the dynamic migration mode of carbon dioxide displacing brine in pore structures is of great significance for assessing the long-term migration and flow process of carbon dioxide in pore structures.

[0003] Currently, in-situ monitoring methods and simulation experiments are insufficient for directly observing the fluid displacement and migration process, making it difficult to study the underground carbon dioxide transport and leakage processes. Furthermore, theoretical assessments suggest that the underground transport of carbon dioxide may take over a thousand years. Since the in-situ high-temperature and high-pressure environment of underground reservoirs makes it difficult to capture such long-term fluid dynamics, and the research costs are high, alternative fluids and accelerated processes using centrifuges are necessary for this study.

[0004] Therefore, how to easily and conveniently observe the displacement and migration process of immiscible fluids in porous structures over a long period of time and effectively shorten the time has become a technical challenge. At present, research and analysis on this process at home and abroad are mostly limited to the simulation level, and there is an urgent need for a set of experimental methods and devices to realize observation and analysis. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention aims to provide a visualized experimental device and method for displacement of porous media under different gravitational conditions. It utilizes the tilt angle of a microfluidic chip to achieve microgravity conditions and the centrifugal force provided by the high-speed rotation of a centrifuge to achieve hypergravity conditions. Large-scale fluid displacement and migration processes can be reconstructed in-situ through scaling and time-lapse effects, and can be observed and analyzed in real time. The experimental method is simple, highly operable, and allows for a deeper understanding of the displacement mechanism of two-phase fluids in porous media, which is of great significance for evaluating the long-term migration and flow process of carbon dioxide in porous structures.

[0006] The technical solution adopted in this invention is as follows:

[0007] I. A visual experimental device for porous media displacement under different gravity conditions:

[0008] The system includes a model housing, a microfluidic chip model module, a displacement injection module, an image acquisition module, and a light source module. All components are housed within the model housing, which is placed inside a centrifuge basket. The displacement injection module stores fluid and is connected to the microfluidic chip model module. The image acquisition module is used to acquire optical image information of the microfluidic chip model module during the fluid displacement process.

[0009] The microfluidic chip model module includes a microfluidic chip, a microfluidic chip fixing fixture, and an adjustable model fixing device. The adjustable model fixing device is installed on the inner bottom surface of the model box shell. The microfluidic chip fixing fixture is installed on the adjustable model fixing device. The adjustable model fixing device is used to adjust the height and angle of the microfluidic chip fixing fixture. The microfluidic chip is installed in the fixing groove of the microfluidic chip fixing fixture. The microfluidic chip includes an injection port, an outlet port, and a porous medium region. The injection port and the outlet port are respectively located on both sides of the porous medium region. The porous medium region is mainly formed by several cylinders of different sizes arranged in a matrix-spaced array.

[0010] The displacement injection module includes a plastic syringe, an injection pump, and a fluid collection device. Both the injection pump and the fluid collection device are installed on the inner bottom surface of the model box shell. The plastic syringe stores fluid. The inlet of the plastic syringe is connected to the injection pump, and the outlet of the plastic syringe is connected to the injection port of the microfluidic chip through a guide tube. The injection pump is connected to an external controller, which controls the injection pump to push the plastic syringe to inject fluid into the microfluidic chip at a certain rate. The outlet of the microfluidic chip is connected to the fluid collection device through a guide tube. The fluid collection device is used to collect the fluid displaced from the microfluidic chip model module during the fluid displacement process.

[0011] The image acquisition module includes an industrial camera and a camera mount. The camera mount mainly consists of a lens support, an industrial camera mount, and a camera base. The front end of the industrial camera is equipped with a lens. The industrial camera and the lens are respectively connected to the industrial camera mount and the lens support. Both the lens support and the industrial camera mount are mounted on the camera base, which is installed on the inner bottom surface of the model box shell. The industrial camera is connected to an external controller.

[0012] The light source module mainly consists of a light source and a light source mounting bracket. The light source is installed inside the model box shell through the light source mounting bracket. The light source is used to provide visible light for imaging of the microfluidic chip model module.

[0013] The device also includes a sealing and heat preservation module, which is mainly composed of a sealing plate and heat preservation material. The sealing plate is installed on the inner surface of the model box shell, and heat preservation material is coated between the inner surface of the model box shell and the sealing plate.

[0014] The microfluidic chip stores the original dyeing fluid, and the plastic syringe of the displacement injection module stores the displacement fluid. The original fluid and the displacement fluid have different densities and viscosities and are immiscible. The original fluid is ethanol, and the displacement fluid is pure carbon dioxide gas or air.

[0015] II. A visual experimental method for displacement of porous media under different gravitational conditions, comprising the following steps:

[0016] Step S1: First, dye the original fluid with dye. Then, load the displacing fluid into another plastic syringe and install it on the injection pump. Install the microfluidic chip in the microfluidic chip fixture. Install the microfluidic chip fixture on the adjustable model fixing device and adjust the installation angle of the microfluidic chip fixture.

[0017] Step S2: Inject the dyed native fluid into the microfluidic chip;

[0018] Step S3: Under different gravity conditions, the controller controls the injection pump to push the plastic syringe to inject displacement fluid into the microfluidic chip at a preset rate;

[0019] Step S4: When the displacing fluid reaches the outlet of the microfluidic chip and flows out to the fluid collection device, the controller receives the image or video information transmitted back by the image acquisition module, and obtains the flow migration mode and fluid distribution of the fluid in the porous medium through the image or video information. Based on the flow migration mode and fluid distribution collected by the simulation test, the analysis of the flow migration mode and fluid distribution under real working conditions is realized.

[0020] The specific steps of S2 are as follows:

[0021] The dyeing native fluid is injected into the microfluidic chip to saturate using a plastic syringe in the displacement injection module. The plastic syringe containing the dyeing native fluid is removed, and another plastic syringe containing the displacement fluid is installed on the injection pump. The outlet of the plastic syringe is connected to the injection port at the bottom of the microfluidic chip through a guide tube, and the outlet at the top of the microfluidic chip is connected to the fluid collection device. The angle and position of the industrial camera in the image acquisition module are adjusted according to the tilt angle of the microfluidic chip.

[0022] Under microgravity conditions, the specific steps of step S3 are as follows:

[0023] The microfluidic chip is adjusted to a preset tilt angle, and then the injection pump is started by the controller. The injection pump pushes the plastic syringe to inject the displacement fluid into the microfluidic chip at a constant speed and pressure. The image acquisition module is used to acquire optical image information of the microfluidic chip in real time during the fluid displacement process.

[0024] Under hypergravity conditions, the specific steps of step S3 are as follows:

[0025] The centrifuge is started, and when the centrifugal acceleration reaches N times the acceleration due to gravity, the control unit controls the injection pump to push the plastic syringe to inject the displacement fluid into the microfluidic chip at a constant speed and pressure. The image acquisition module is used to collect optical image information of the microfluidic chip in real time during the fluid displacement process.

[0026] This invention provides a device that can utilize a centrifuge to provide high centrifugal acceleration for scaled-down and time-lapse model experiments of porous structures. It can also provide microgravity conditions for porous structure model experiments by customizing an adjustable model fixing module. The device enables real-time observation of the dynamic behavior of two-phase displacement processes in porous structures, allowing analysis of the displacement mechanism of two-phase fluids in porous media to understand and predict in-situ fluid displacement patterns. The device is simple to fabricate, easy to operate, and highly stable. By utilizing both hypergravity and microgravity for model experiments, it achieves real-time observation of two-phase fluid displacement processes.

[0027] This invention utilizes scaled-down models of porous structures under different gravity environments. A transparent microfluidic chip simulates porous media, and an image acquisition module observes the dynamic behavior of the two-phase displacement process in the porous structure in real time. It analyzes the fluid migration patterns and distribution during the displacement process in porous media, providing an easy-to-operate and low-cost experimental method for studying the mechanism of fluid displacement at the pore scale. This invention allows for different experiments by controlling the injection pump to change the injection flow rate, adjusting the microfluidic chip angle to achieve microgravity, and controlling a centrifuge to achieve hypergravity, analyzing the flow pattern transformation modes of fluid displacement in porous media under different conditions.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. This invention utilizes an image acquisition module to visualize the fluid displacement process, making it easy to analyze the fluid flow migration and flow pattern transformation modes generated during this process.

[0030] 2. This invention achieves microgravity by adjusting the angle of the microfluidic chip and achieves hypergravity by using a hypergravity centrifuge to provide high centrifugal acceleration, which can effectively reflect the two-phase fluid displacement process of porous media at the field scale.

[0031] 3. This invention can change the influencing factors of fluid displacement, including injection rate, injection pressure, permeability, gravitational acceleration, etc., and can perform single-phase fluid displacement and multi-phase fluid displacement. The experimental device and method are simple, convenient, highly operable and low in cost.

[0032] 4. This invention utilizes the advantages of microfluidic chips, such as high plasticity and repeatability, to randomly set pore structures and reproduce the pore characteristics of real-world rock masses.

[0033] 5. This invention is of great significance for studying the mechanism of two-phase fluid displacement process in porous media, and has important guiding significance for the safety of carbon dioxide geological storage projects and improving oilfield oil recovery rate. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the operation of the experimental device of the present invention;

[0035] Figure 2 This is a side view of the structure of the device model box of the present invention;

[0036] Figure 3 This is a schematic diagram of the structure of the visualized microfluidic chip model module of the present invention.

[0037] In the diagram: Ⅰ-Model box shell; Ⅱ-Microfluidic chip model module; Ⅲ-Displacement injection module; Ⅳ-Image acquisition module; Ⅴ-Controller; Ⅵ-Centrifuge; Ⅶ-Counterweight; 1-Microfluidic chip fixing fixture; 2-Industrial camera; 3-Plastic syringe; 4-Injection pump; 5-Fluid collection device; 6-Camera mount; 7-Adjustable model fixing device; 8-Light source; 9-Light source mount; 10-Fixing platform; 11-Sealing and insulation module; 12-Guide tube; 13-Bolt; 14-Hexagonal screw; 15-Upper fixing plate; 16-Lens support frame; 17-Injection port; 18-Porous media area; 19-Outlet; 20-Microfluidic chip. Detailed Implementation

[0038] The present invention will be described in detail below with reference to specific implementation examples. These examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way.

[0039] like Figure 1 As shown, the device includes a model box shell I, a microfluidic chip model module II, a displacement injection module III, an image acquisition module IV, and a light source module. The microfluidic chip model module II is used to simulate the displacement process of two-phase fluid in a porous medium. The microfluidic chip model module II, the displacement injection module III, the image acquisition module IV, and the light source module are all placed inside the model box shell I, which is placed inside the basket of centrifuge VI. The displacement injection module III stores fluid and is connected to the microfluidic chip model module II to provide fluid to the microfluidic chip model module II. The image acquisition module IV is used to acquire optical image information of the microfluidic chip model module II during the fluid displacement process.

[0040] Centrifuge VI comprises two baskets and a base. The two baskets are fixedly mounted on opposite sides of the centrifuge VI base via rotating arms, initially pointing vertically downwards. The model box shell I is placed inside one basket of centrifuge VI, while the counterweight VII is placed in the basket on the other side. A control unit V is electrically connected to centrifuge VI and drives centrifuge VI to rotate. As centrifuge VI rotates, the baskets slowly rise to a horizontal position. The rotating arms then drive the baskets to rotate together, providing high centrifugal acceleration. Centrifuge VI provides a hypergravity environment equivalent to high gravitational acceleration, enabling the reconstruction of large-scale fluid displacement processes in real-world conditions using a scaled-down and time-lapse effect. Counterweight VII balances model box I to maintain the mass balance of the baskets on both sides of centrifuge VI.

[0041] like Figure 3 As shown, the microfluidic chip model module II includes a microfluidic chip 20, a microfluidic chip fixing fixture 1, and an adjustable model fixing device 7. The adjustable model fixing device 7 is installed on the inner bottom surface of the model box shell I via a fixing platform 10. The microfluidic chip fixing fixture 1 is installed on the adjustable model fixing device 7 via hexagonal screws 14. The adjustable model fixing device 7 is used to adjust the height and angle of the microfluidic chip fixing fixture 1. A fixing groove is provided in the middle of the microfluidic chip fixing fixture 1. The microfluidic chip 20 is installed in the fixing groove of the microfluidic chip fixing fixture 1. The microfluidic chip 20 includes an injection port 17, an outlet port 19, and a porous medium region 18. The injection port 17 and the outlet port 19 are respectively located on the lower and upper sides of the porous medium region 18. The porous medium region 18 is mainly formed by several cylinders of different sizes arranged in a matrix-spaced array.

[0042] The microfluidic chip 20 is a key component of the device of this invention, and is fabricated using a transparent glass material through an etching process. Based on the designed microfluidic channel planar pattern, microfluidic channels (i.e., porous media region 18) are etched to simulate the pores between particles in real rock or soil, thus mimicking the actual working conditions of real rock or soil. The designed microfluidic channels aim to reproduce the internal structure of real rock or soil, allowing for detailed studies of fluid displacement and migration within the rock or soil. For different fluids such as water, oil, and organic solvents, the chip material needs to be selected, and targeted chemical modifications or coatings are required. The adjustable model fixing device 7 is used to fix the microfluidic chip 20, ensuring that the microfluidic chip 20 and the industrial camera 2 are on the same horizontal plane.

[0043] like Figure 2As shown, the displacement injection module III includes a plastic syringe 3, an injection pump 4, and a fluid collection device 5. Both the injection pump 4 and the fluid collection device 5 are mounted on the inner bottom surface of the model box shell I via a fixed platform 10. The plastic syringe 3 stores fluid. The inlet of the plastic syringe 3 is connected to the injection pump 4, and the outlet of the plastic syringe 3 is connected to the injection port 17 of the microfluidic chip 20 via a guide tube 12. The injection pump 4 is externally connected to a controller V, which controls the injection pump 4 to push the plastic syringe 3 to inject displacement fluid into the microfluidic chip 20 at a certain rate. The outlet 19 of the microfluidic chip 20 is connected to the fluid collection device 5 via the guide tube 12. The fluid collection device 5 is used to collect the fluid displaced from the microfluidic chip model module II during the fluid displacement process.

[0044] In practice, the constant speed and pressure characteristics of the syringe pump 4 can be used to precisely control the flow rate of fluid entering the microfluidic chip 20, ensuring that the fluid passes through the microfluidic channel of the microfluidic chip 20 at a stable rate during the experiment. The fluid collection device 5 includes an L-shaped bracket and centrifuge tubes. The L-shaped bracket is fixedly connected to the fixed platform 10 by bolts 13. The fixed platform 10 is fixed to the inner bottom surface of the model box shell I. The centrifuge tubes are tied to the L-shaped bracket by straps to prevent the rotation of the centrifuge VI from affecting fluid collection.

[0045] Image acquisition module IV includes an industrial camera 2 and a camera mount 6. The camera mount 6 mainly consists of a lens support frame 16, an industrial camera mount, and a camera base. The front end of the industrial camera 2 is equipped with a lens. The industrial camera 2 and the lens at the front end of the industrial camera 2 are respectively connected to the industrial camera mount and the lens support frame 16. The lens support frame 16 and the industrial camera mount are both mounted on the camera base. The camera base is mounted on the inner bottom surface of the model box shell I through a fixing platform 10. The industrial camera 2 is connected to an external control unit V.

[0046] The lens support 16 is connected to the middle of the lens. The shooting angle of the industrial camera 2 can be changed by adjusting the height of the lens support 16, ultimately ensuring that the microfluidic chip model module II is centered in the field of view. The image acquisition module IV is mainly used to capture the two-phase fluid displacement process and obtain the displacement mechanism of the fluid in the porous medium. The displacement injection module III is used to inject the original fluid and the displacement fluid during the experiment.

[0047] The light source module mainly consists of a light source 8 and a light source mounting bracket 9. The light source 8 is installed inside the model box shell I through the light source mounting bracket 9. The light source 8 is used to provide visible light for imaging of the microfluidic chip model module II.

[0048] Light source 8 is used to provide uniform and stable light intensity during the experiment. Light source 8 uses LEDs arranged in multiple points. Light source mounting bracket 9 is installed on the inner bottom surface of the model box shell I via mounting platform 10. Light source mounting bracket 9 is used to fix light source 8 to the back of microfluidic chip model module II, so that the center of light source 8 is aligned with the center of microfluidic chip model module II.

[0049] The device also includes a sealing and heat preservation module 11, which is mainly composed of a sealing plate and heat preservation material. The sealing plate is installed on the inner surface of the model box shell I, and heat preservation material is coated between the inner surface of the model box shell I and the sealing plate. The sealing and heat preservation module 11 is used for light shielding and heat preservation during the test.

[0050] The fixed platform 10 is used to form an experimental system in conjunction with the camera mount 6, the adjustable model fixing device 7, the displacement injection module III, and the sealing and insulation module 11. The camera mount 6, the adjustable model fixing device 7, and the displacement injection module III are all connected to the fixed platform 10 by bolts 13. The injection pump 4 is connected to the control center of the control unit V via wires and the centrifuge optical transceiver. The image acquisition module IV is connected to the control center of the control unit V via wires.

[0051] The adjustable model fixing device 7 is used to fix the microfluidic chip 20, ensuring that the microfluidic chip 20 and the industrial camera 2 are on the same horizontal line. The adjustable model fixing device 7 includes a front fixing plate and an upper fixing plate 15. The front fixing plate has side openings to fix the microfluidic chip fixing fixture 1. The specific opening angle can be determined by the distance between the side openings of the microfluidic chip fixing fixture 1 and the desired microgravity value, allowing the microfluidic chip 20 to be tilted at a certain angle for fluid displacement experiments under microgravity conditions. The acceleration under microgravity conditions is less than the acceleration under normal gravity g, specifically gsinθ, where θ is the angle between the microfluidic chip 20 and the ground, which can be achieved by tilting the microfluidic chip 20 at a certain angle. The upper fixing plate 15 is used to connect and fix the front fixing plate and the light source fixing bracket 9, avoiding disturbances during the experiment. The base of the adjustable model fixing device 7 can be adjusted forward and backward to make the camera capture clearer images.

[0052] The microfluidic chip 20 stores the dyed native fluid, and the plastic syringe 3 of the displacement injection module III stores the displacement fluid. The native fluid and the displacement fluid have different densities and viscosities and are immiscible. The native fluid is dyed ethanol, and the displacement fluid is pure carbon dioxide gas or air.

[0053] Embodiments of the present invention include the following steps:

[0054] Step S1: First, dye the original fluid (ethanol) with dye. Then, load a displacing fluid (carbon dioxide or air) that is different in density and viscosity from the original fluid and is immiscible into another plastic syringe and install the plastic syringe on the injection pump 4. Install the microfluidic chip 20 in the microfluidic chip fixing fixture 1. Install the microfluidic chip fixing fixture 1 with the microfluidic chip 20 on the adjustable model fixing device 7 and adjust the installation height and angle of the microfluidic chip fixing fixture 1 according to the preset angle.

[0055] Step S2: Inject the dyed native fluid into the microfluidic chip 20;

[0056] Step S3: Under different gravity conditions, the control unit V controls the injection pump 4 to push the plastic syringe 3 to inject the displacement fluid into the microfluidic chip 20 at a certain rate;

[0057] Step S4: When the displacing fluid reaches the outlet 19 of the microfluidic chip 20 and flows out to the fluid collection device 5, the porous media displacement test under different gravity conditions ends. The controller V receives the image or video information transmitted back by the image acquisition module IV, and obtains the flow migration mode and fluid distribution of the fluid in the porous media displacement process through the image or video information. Based on the flow migration mode and fluid distribution collected by the simulation test, the analysis of the flow migration mode and fluid distribution under real working conditions is realized.

[0058] Step S2 is as follows:

[0059] The dyeing native fluid is injected into the microfluidic chip 20 to saturate using the plastic syringe 3 in the displacement injection module III. The plastic syringe 3 containing the dyeing native fluid is removed, and another plastic syringe 3 containing the displacement fluid is switched and installed on the injection pump 4. The outlet of the plastic syringe 3 is connected to the injection port 17 at the bottom of the microfluidic chip 20 through the guide tube 12, and the outlet port 19 at the top of the microfluidic chip 20 is connected to the fluid collection device 5. The light source 8 in the light source module is turned on, and the angle and position of the industrial camera 2 in the image acquisition module IV are adjusted according to the tilt angle of the microfluidic chip 20 to calibrate the image of the industrial camera 2. The sealing plate is closed using bolts 13.

[0060] Under microgravity conditions, the specific steps of step S3 are as follows:

[0061] Adjust the microfluidic chip (20) to a preset tilt angle, start the injection pump 4 using the controller V, so that the injection pump 4 pushes the plastic syringe 3 to inject the displacement fluid into the microfluidic chip 20 at a constant speed and pressure, and use the image acquisition module IV to acquire the optical image information of the microfluidic chip 20 in real time during the fluid displacement process;

[0062] Under hypergravity conditions, the specific steps of step S3 are as follows:

[0063] Centrifuge VI is started. When the centrifugal acceleration reaches N times the gravitational acceleration, the control unit V controls the injection pump 4 to push the plastic syringe 3 to inject the displacement fluid into the microfluidic chip 20 at a constant speed and pressure. The image acquisition module IV is used to acquire optical image information of the microfluidic chip 20 in real time during the fluid displacement process.

[0064] The displacing fluid enters through the inlet 17 at the bottom of the microfluidic chip 20 via the guide tube 12. The displacement process of the fluid inside the microfluidic chip 20 is influenced by gravity, viscous force, and capillary force, ultimately selecting the optimal path for displacement. The image acquisition module IV can acquire the fluid displacement process inside the microfluidic chip 20 in real time. This invention can conduct experiments under different conditions by changing the angle of the microfluidic chip 20, the fluid velocity, the entry pressure, and the gravitational acceleration. It can analyze the flow pattern transformation mode of the fluid displacement process in the porous medium under different conditions, and then draw an analogy to the fluid displacement mode at the field scale.

[0065] This invention utilizes scaled-down model experiments of porous structures under different gravity environments. By leveraging the scaling and time-lapse effects of hypergravity fields, it recreates the large-scale fluid displacement and migration process in the field. Real-time observation and recording methods are used to understand the displacement mechanism of two-phase fluids in porous media. This is of great significance for evaluating the long-term migration and flow process of carbon dioxide in porous structures.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A visual experimental method for displacement of porous media under different gravitational conditions, characterized in that, The method employs a visualization experimental device, which includes a model box shell (Ⅰ), a microfluidic chip model module (Ⅱ), a displacement injection module (Ⅲ), an image acquisition module (Ⅳ), and a light source module. The microfluidic chip model module (Ⅱ), the displacement injection module (Ⅲ), the image acquisition module (Ⅳ), and the light source module are all placed inside the model box shell (Ⅰ). The model box shell (Ⅰ) is placed inside the basket of a centrifuge (Ⅵ). The displacement injection module (Ⅲ) stores fluid and is connected to the microfluidic chip model module (Ⅱ). The image acquisition module (Ⅳ) is used to acquire optical image information of the microfluidic chip model module (Ⅱ) during the fluid displacement process. The microfluidic chip model module (II) includes a microfluidic chip (20), a microfluidic chip fixing fixture (1), and an adjustable model fixing device (7); the adjustable model fixing device (7) is installed on the inner bottom surface of the model box shell (I), the microfluidic chip fixing fixture (1) is installed on the adjustable model fixing device (7), the adjustable model fixing device (7) is used to adjust the height and angle of the microfluidic chip fixing fixture (1), the microfluidic chip (20) is installed in the fixing groove of the microfluidic chip fixing fixture (1), the microfluidic chip (20) includes an injection port (17), an outlet port (19), and a porous medium region (18), the injection port (17) and the outlet port (19) are respectively set on both sides of the porous medium region (18), the porous medium region (18) is mainly formed by several cylinders of different sizes arranged in a matrix interval array; The device also includes a sealing and heat preservation module (11), which is mainly composed of a sealing plate and heat preservation material. The inner surface of the model box shell (I) is equipped with a sealing plate, and heat preservation material is coated between the inner surface of the model box shell (I) and the sealing plate. The microfluidic chip (20) stores the original dyeing fluid, and the plastic syringe (3) of the displacement injection module (Ⅲ) stores the displacement fluid. The original fluid and the displacement fluid have different densities and viscosities and are immiscible. The original fluid is ethanol, and the displacement fluid is pure carbon dioxide gas or air. The microfluidic chip (20) is made of transparent glass material by etching process; The adjustable model fixing device (7) includes a front fixing plate and an upper fixing plate (15). The front fixing plate has a side opening to fix the microfluidic chip fixing fixture (1). The specific opening angle is determined by the side opening distance of the microfluidic chip fixing fixture (1) and the value of the desired microgravity, so that the microfluidic chip (20) is tilted at a certain angle to conduct a fluid displacement test under microgravity conditions. The acceleration under microgravity conditions is less than the acceleration under normal gravity g, which is achieved by tilting the microfluidic chip (20) at a certain angle. The method includes the following steps: Step S1: First, dye the original fluid with dye, then load the displacing fluid into another plastic syringe and install it on the injection pump (4), install the microfluidic chip (20) in the microfluidic chip fixing fixture (1), install the microfluidic chip fixing fixture (1) on the adjustable model fixing device (7), and adjust the installation angle of the microfluidic chip fixing fixture (1); Step S2: Inject the dyed native fluid into the microfluidic chip (20); Step S3: Under different gravity conditions, the controller (V) controls the injection pump (4) to push the plastic syringe (3) to inject the displacement fluid into the microfluidic chip (20) at a preset rate; Step S4: When the displacing fluid reaches the outlet (19) of the microfluidic chip (20) and flows out to the fluid collection device (5), the controller (V) receives the image or video information transmitted back by the image acquisition module (Ⅳ), and obtains the flow migration mode and fluid distribution of the fluid in the porous medium through the image or video information. Based on the flow migration mode and fluid distribution collected by the simulation test, the analysis of the flow migration mode and fluid distribution under real working conditions is realized. Under microgravity conditions, the specific steps of step S3 are as follows: Adjust the microfluidic chip (20) to a preset tilt angle, then use the controller (V) to start the injection pump (4), so that the injection pump (4) pushes the plastic syringe (3) to inject the displacement fluid into the microfluidic chip (20) at a constant speed and pressure, and use the image acquisition module (IV) to acquire the optical image information of the microfluidic chip (20) in the fluid displacement process in real time; Under hypergravity conditions, the specific steps of step S3 are as follows: Start the centrifuge (VI). When the centrifugal acceleration reaches N times the gravitational acceleration, use the controller (V) to control the injection pump (4) to push the plastic syringe (3) to inject the displacement fluid into the microfluidic chip (20) at a constant speed and pressure. Use the image acquisition module (IV) to collect the optical image information of the microfluidic chip (20) in real time during the fluid displacement process.

2. The visual experimental method for displacement of porous media under different gravity conditions according to claim 1, characterized in that: The specific steps of S2 are as follows: The dyeing native fluid is injected into the microfluidic chip (20) to saturate using the plastic syringe (3) in the displacement injection module (Ⅲ). The plastic syringe (3) containing the dyeing native fluid is removed, and another plastic syringe containing the displacement fluid is installed on the injection pump (4). The outlet of the plastic syringe (3) is connected to the injection port (17) at the bottom of the microfluidic chip (20), and the outlet (19) at the top of the microfluidic chip (20) is connected to the fluid collection device (5). The angle and position of the industrial camera (2) in the image acquisition module (Ⅳ) are adjusted according to the tilt angle of the microfluidic chip (20).

3. The visual experimental method for displacement of porous media under different gravity conditions according to claim 1, characterized in that: The displacement injection module (Ⅲ) includes a plastic syringe (3), an injection pump (4), and a fluid collection device (5). The injection pump (4) and the fluid collection device (5) are both installed on the inner bottom surface of the model box shell (Ⅰ). The plastic syringe (3) stores fluid. The inlet of the plastic syringe (3) is connected to the injection pump (4). The outlet of the plastic syringe (3) is connected to the injection port (17) of the microfluidic chip (20) through the guide tube (12). The injection pump (4) is connected to an external controller (Ⅴ). The controller (Ⅴ) is used to control the injection pump (4) to push the plastic syringe (3) to inject fluid into the microfluidic chip (20). The outlet (19) of the microfluidic chip (20) is connected to the fluid collection device (5) through the guide tube (12). The fluid collection device (5) is used to collect the fluid displaced from the microfluidic chip model module (Ⅱ) during the fluid displacement process.

4. The visual experimental method for displacement of porous media under different gravity conditions according to claim 1, characterized in that: The image acquisition module (Ⅳ) includes an industrial camera (2) and a camera mount (6). The camera mount (6) is mainly composed of a lens support frame (16), an industrial camera mount and a camera base. The front end of the industrial camera (2) is equipped with a lens. The industrial camera (2) and the lens are respectively connected to the industrial camera mount and the lens support frame (16). The lens support frame (16) and the industrial camera mount are both installed on the camera base. The camera base is installed on the inner bottom surface of the model box shell (Ⅰ). The industrial camera (2) is connected to an external controller (Ⅴ).

5. The visual experimental method for displacement of porous media under different gravity conditions according to claim 1, characterized in that: The light source module mainly consists of a light source (8) and a light source mounting bracket (9). The light source (8) is installed inside the model box shell (Ⅰ) through the light source mounting bracket (9). The light source (8) is used to provide visible light for imaging of the microfluidic chip model module (Ⅱ).

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