Visualized experimental apparatus and method for measuring dynamic capillary forces in low permeability tight reservoirs

Abstract

The application discloses a kind of visual experiment device and method for measuring low-permeability tight reservoir dynamic capillary force, belong to oil and gas exploitation experimental technical field, device includes visual microcosmic model, constant-pressure constant-speed displacement unit, pressure detection unit, image acquisition unit, temperature control unit and computer, visual microcosmic model includes transparent shell and its inside porous medium main body, constant-pressure constant-speed displacement unit is connected with visual microcosmic model;Method is to use constant-pressure constant-speed displacement unit to inject fluid into visual microcosmic model, so that its inside forms confining pressure;Pressure detection unit detects the pressure of different positions of visual microcosmic model, and image acquisition unit acquires the image of fluid distribution and displacement process inside visual microcosmic model;Temperature control unit adjusts the temperature of visual microcosmic model, and data is analyzed by computer.The application realizes the dual support of visual observation and accurate pressure data, and can analyze the relationship between dynamic capillary force and pressure change.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction experimental technology, and in particular relates to a visualization experimental device and method for measuring dynamic capillary forces in low-permeability tight reservoirs. Background Technology

[0002] As conventional oil and gas resources account for a smaller and smaller proportion of the total global oil and gas resources, low-permeability oil and gas resources will become an important area for oil and gas exploration and development. my country has a wide distribution and large reserves of low-permeability oil and gas resources, which occupy a very important position in oil and gas exploration and development. The proportion of reserves and production of low-permeability oil and gas fields is increasing year by year, and they have become the main resources for increasing oil and gas reserves and production.

[0003] The exploration and development process of low-permeability tight oil reservoirs differs significantly from that of medium- and high-permeability oil reservoirs. The oil-water distribution and seepage patterns in low-permeability tight oil reservoirs are complex, with features such as an initial pressure gradient and non-Darcy flow. Currently, the development process faces a series of challenges, including low water absorption capacity of injection wells, high initial pressure gradient and injection pressure, slow well activation, and a significant drop in the oil production index after water breakthrough.

[0004] The main reasons for the above problems are that the low-permeability tight reservoir is highly heterogeneous, with uneven pore distribution, and the capillary pressure has a significant impact on fluid flow. The water propulsion speed is uneven, and it is accompanied by severe liquid resistance and Jamin effect. Therefore, the injected water mainly rushes along fractures and large channels, which easily causes flow around and blockage when crude oil seeps in, resulting in a large amount of crude oil retention, reduced oil displacement efficiency, high water content in produced fluid, and increased extraction costs. The interfacial properties have a crucial impact on oil-water flow, especially the capillary pressure, which plays an indispensable role in oil retention and displacement.

[0005] The microscopic interaction forces between the rock wall and the fluid, namely capillary pressure and viscosity, influence macroscopic development characteristics. Low-permeability tight reservoirs have fine pores, ranging from micrometers to nanometers, with large specific surface areas and complex pore structures. The capillary pressure and viscosity within these pores differ significantly from those in medium- and high-permeability reservoirs, significantly impacting fluid distribution and waterflood recovery rates. This leads to high injection pressure, low oil displacement efficiency, and poor development outcomes. Therefore, effectively controlling and utilizing capillary pressure can significantly improve reservoir waterflooding performance.

[0006] Capillary pressure refers to the pressure difference between the unwetting and wetting phases on both sides of a meniscus in a capillary. It can be broadly classified into static capillary pressure, steady-state capillary pressure, and dynamic capillary pressure. For high-permeability and medium-permeability reservoirs, the dynamic capillary effect is negligible. However, for low-permeability tight reservoirs, due to their characteristics, they exhibit complex multi-scale pore structures with strong heterogeneity and significant nano-effects in the matrix pores, leading to complex nonlinear flow behavior. Existing research shows that enhanced heterogeneity strengthens the dynamic capillary effect, and the dynamic capillary effect coefficient increases with decreasing pore size. Therefore, the dynamic capillary effect is strong in low-permeability tight sandstone reservoirs. Thus, accurate measurement of capillary pressure is a necessary step in understanding reservoirs and developing water injection development plans.

[0007] Static capillary pressure and steady-state capillary pressure refer to capillary pressure measured under static or steady-state conditions. However, static capillary pressure needs to be obtained when the fluid flow is very slow and the oil-water interface is nearly static, which usually takes several weeks or even months. Steady-state capillary pressure is obtained when the fluid flow reaches equilibrium and the water saturation does not change over time.

[0008] Under normal conditions, the seepage during water injection is unstable, i.e., a dynamic process. Studying actual dynamic displacement using steady-state capillary pressure introduces errors, while using static capillary pressure results in even greater errors. Fluid flow in an oil reservoir is influenced by the dynamic capillary effect, and the capillary pressure exerted on the fluid flow is the dynamic capillary pressure.

[0009] Dynamic capillary pressure (DCP) refers to the capillary pressure under unstable flow conditions during displacement, and it is of great significance for predicting the two-phase flow behavior in porous media. Dynamic capillary pressure is the capillary pressure measured before equilibrium is reached. Currently, most commonly used methods for measuring dynamic capillary pressure are based on a modified testing device and method developed by Kalaydjian in 1992. This involves placing the core vertically and wrapping it with epoxy resin, with pressure sensor probes covered by a semi-permeable membrane (water-wet or oil-wet) on both sides of the core. The pressure sensors can automatically measure the in-situ pressure of the oil and water phases and the total pressure difference of the core. However, this testing method cannot exceed 10 psi in displacement pressure, making it unsuitable for experiments on low-permeability cores, and it cannot apply reservoir conditions. Furthermore, it lacks a microscopic visualization observation system to compare and observe changes in the liquid level during capillary pressure changes. Therefore, there is an urgent need to design a microscopic visualization device and method for measuring dynamic capillary force. Summary of the Invention

[0010] The purpose of this invention is to provide a visual experimental device and method for measuring dynamic capillary force in low-permeability tight reservoirs. This invention aims to solve the technical problems of existing devices for testing dynamic capillary pressure having low displacement pressure, being unable to conduct experiments on low-permeability cores, being unable to apply reservoir conditions, and being unable to make intuitive observations.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0012] A visualization experimental device for measuring dynamic capillary forces in low-permeability tight reservoirs includes a visualization micro-model, a constant-pressure and constant-rate displacement unit, a pressure detection unit, an image acquisition unit, a temperature control unit, and a computer. The visualization micro-model comprises a transparent outer shell and a porous media body inside, with a water-filled intermediate region between the outer shell and the porous media body capable of creating confining pressure. The constant-pressure and constant-rate displacement unit is connected to the visualization micro-model and is used to inject fluid into the visualization micro-model. The pressure detection unit is used to detect the pressure at different locations within the visualization micro-model. The image acquisition unit is used to acquire images of the fluid distribution and displacement process within the visualization micro-model. The temperature control unit is used to control the temperature of the visualization micro-model. The constant-pressure and constant-rate displacement unit, pressure detection unit, image acquisition unit, and temperature control unit are all connected to the computer.

[0013] Preferably, the outer shell includes an open-top shell and a porous media cover plate and an upper cover plate on its top. The porous media cover plate is disposed on the top of the porous media body, and the two are engaged with each other around their edges. Both the porous media body and the porous media cover plate are disposed inside the shell. The upper cover plate is disposed on the top of the shell, and the edge of the upper cover plate is connected to the four sides of the shell by bolts. The bottom of the shell is provided with a drain port, and two opposite side walls are respectively provided with an inlet and an outlet that can be connected to a constant pressure and constant speed displacement unit. The other two side walls are connected to a pressure detection unit. The top of the upper cover plate is provided with a water injection port that can be connected to the constant pressure and constant speed displacement unit. Water is injected into the confining pressure cavity between the upper cover plate, the shell, and the porous media body through the water injection port to form confining pressure.

[0014] Preferably, the constant pressure and constant speed displacement unit includes a constant pressure and constant speed displacement pump, a pressure control system, and connecting pipelines. The constant pressure and constant speed displacement pump is connected to the inlet of the intermediate container and the shell through the connecting pipelines, and is used to inject fluid into the visualized microscopic model. The outlet of the shell is connected to the liquid sampling container through the connecting pipelines. The pressure control system includes a water injection pump and a pressure controller. The water injection pump is connected to the water injection port on the upper cover plate through the connecting pipelines. The pressure controller is connected to the pressure detection unit and the water injection pump, and is used to monitor the confining pressure in the visualized microscopic model in real time.

[0015] Preferably, the pressure detection unit includes several pressure sensors, and several pressure measurement ports are provided on the two opposite side walls of the housing for installing pressure sensors; the pressure sensors are connected to a pressure controller to monitor pressure changes in different areas inside the housing and collect pressure data.

[0016] Preferably, the image acquisition unit includes a camera and a robotic arm, with the camera positioned at the end of the robotic arm, and the robotic arm used to drive the camera to move above the visualized microscopic model.

[0017] Preferably, the temperature control unit includes a constant temperature chamber and a temperature controller connected thereto, and the visualized microscopic model is disposed on the top of the constant temperature chamber.

[0018] Preferably, the visualized microscopic model is provided with an oleophilic semi-permeable membrane or a hydrophilic semi-permeable membrane. The oleophilic semi-permeable membrane or the hydrophilic semi-permeable membrane is disposed between the inlet of the shell and the porous medium body, so that only the oil phase or water phase enters the porous medium body, for testing the pressure of the oil phase or water phase.

[0019] This invention also provides a visual experimental method for measuring dynamic capillary forces in low-permeability tight reservoirs, comprising the following steps:

[0020] Assemble the above-mentioned visualization experimental setup;

[0021] The initial parameters of the fluid injected into the constant pressure and constant speed displacement unit were set according to the experimental requirements: injection speed and injection volume.

[0022] The pressure detection unit is activated to inject water into the confining pressure chamber of the visualized microscopic model to form confining pressure, and the confining pressure is maintained 5 MPa higher than the displacement pressure.

[0023] The constant pressure and constant speed displacement pump of the constant pressure and constant speed displacement unit is started to sequentially inject saturated formation water and formation crude oil into the visualized micro model;

[0024] The constant pressure and constant speed displacement pump was restarted to inject displacement fluid into the visualized micro model at the set injection rate and volume. The pressure and flow rate of the injected fluid, as well as the pressure of the oil and water phases at each pressure detection port on the visualized micro model, were monitored and the experimental data were recorded. The dynamic capillary force and water saturation in the porous medium were measured.

[0025] Stop when the injected displacement fluid reaches the set injection volume;

[0026] After the experiment, open the drain valve, remove the confining pressure, and disassemble and clean the visualization experimental device for later use.

[0027] Preferably, the pressure difference between the oil phase and the water phase is the dynamic capillary force within the porous medium body. The oil production and water production at the outlet on the shell are measured to obtain the cumulative oil production and cumulative water production; the water saturation is also measured.

[0028] The relationship between dynamic capillary force and water saturation is as follows:

[0029]

[0030] In the formula: Fc is the dynamic capillary force;

[0031] Sw represents water saturation.

[0032] Compared with the prior art, the beneficial effects of this invention are as follows:

[0033] This invention utilizes a high-pressure resistant, visualized microscopic model paired with an adjustable image acquisition unit to capture high-definition fluid distribution and displacement processes within a porous medium. Simultaneously, a pressure detection unit monitors and acquires data in real-time from different regions within the visualized microscopic model, providing dual support for both visual observation and precise pressure data. This enables the analysis of the relationship between dynamic capillary force-related fluid behavior and pressure changes, resolving issues of data ambiguity or missing observations in existing methods. Furthermore, a constant-pressure, constant-rate displacement unit precisely controls the injection pressure and flow rate of the displacement fluid, allowing the confining pressure to dynamically change with the displacement pressure. A temperature control system flexibly adjusts the experimental temperature, simulating real-world scenarios under different pressures and temperatures. This overcomes the limitations of existing methods, which rely on single experimental conditions and are difficult to adapt to complex working conditions, thus improving the applicability of the measurement results. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0035] In the attached diagram:

[0036] Figure 1 This is a schematic diagram of the structure of a visualization experimental device for measuring dynamic capillary forces in low-permeability tight reservoirs, provided in an embodiment of the present invention.

[0037] Figure 2 for Figure 1 Process flow diagram of the visual experimental device;

[0038] Figure 3 This is an external view of the visualized microscopic model in an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the structure of the upper cover plate in an embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the shell structure in an embodiment of the present invention;

[0041] Figure 6 This is a schematic diagram showing the arrangement of the porous media body within the housing in an embodiment of the present invention;

[0042] Figure 7 This is a schematic diagram showing the relative positions of the porous medium cover plate and the upper cover plate in an embodiment of the present invention;

[0043] Figure 8 This is a schematic diagram of the bolt pair in an embodiment of the present invention;

[0044] Figure 9 This is a schematic diagram illustrating the installation process of the visualized microscopic model in an embodiment of the present invention;

[0045] Figure 10 This is a schematic diagram illustrating the process of injecting water into a visualized microscopic model to form confining pressure in an embodiment of the present invention;

[0046] Figure 11 The curves showing the dynamic capillary force variation under different water saturation levels;

[0047] In the picture:

[0048] 1-Computer; 2-Camera; 3-Outlet; 4-Liquid collection container; 5-Pressure measurement end; 6-Visual microscopic model; 7-Temperature control unit; 8-Inlet; 9-Water injection pump; 10-Constant pressure and constant speed displacement pump; 11-Intermediate container; 12-Bolt mounting hole; 13-Water injection port; 14-Top cover plate; 15-Shell; 16-Snap-fit ​​structure; 17-Porous media body; 18-Porous media cover plate; 19-Bolt; 20-Nut; 21-Confining pressure chamber; 22-Pressure controller; 23-Robotic arm; 24-Confining pressure detection port. Detailed Implementation

[0049] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. In the following detailed description of the invention, certain specific details are described in detail. However, those skilled in the art will fully understand the invention for any parts not described in detail.

[0050] Furthermore, those skilled in the art should understand that the accompanying drawings are provided only to illustrate the purpose, features, and advantages of the present invention, and are not actually drawn to scale.

[0051] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0052] like Figure 1 , Figure 2 As shown in the figure, an embodiment of the present invention provides a visualization experimental device for measuring dynamic capillary forces in low-permeability tight reservoirs, comprising a visualization micro-model 6, a constant pressure and constant rate displacement unit, a pressure detection unit, an image acquisition unit, a temperature control unit 7, and a computer 1. The visualization micro-model 6 includes a transparent high-pressure resistant outer shell and a porous media body 17 inside. The intermediate region (confining pressure chamber 21) between the outer shell and the porous media body 17 can be injected with water to form confining pressure. The constant pressure and constant rate displacement unit is connected to the visualization micro-model 6 and is used to inject fluid into the visualization micro-model 6. The pressure detection unit is used to detect the pressure at different locations of the visualization micro-model 6. The image acquisition unit is used to acquire images of the fluid distribution and displacement process inside the visualization micro-model 6. The temperature control unit 7 is used to control the temperature of the visualization micro-model 6. The constant pressure and constant rate displacement unit, the pressure detection unit, the image acquisition unit, and the temperature control unit 7 are all connected to the computer 1. A porous medium substrate 17 was used to simulate the core of a low-permeability tight reservoir. The temperature of the visualized micro-model was adjusted by a temperature control unit, and the pressure in different regions of the visualized micro-model was monitored and data was acquired in real time by a pressure detection unit. During the experiment, images of fluid distribution and displacement process in the porous medium substrate of the micro-model were acquired by an image acquisition unit.

[0053] In specific embodiments of the present invention, such as Figure 3-7 As shown, the outer casing includes a shell 15 with an open top and a porous media cover plate 18 and an upper cover plate 14 on its top. The porous media cover plate 18 is disposed on the top of the porous media body 17, and the two are engaged with each other at their four edges. The porous media body 17 and the porous media cover plate 18 are both disposed inside the shell 15. The upper cover plate 14 is disposed on the top of the shell 15, and the edge of the upper cover plate 14 is connected to the four sides of the shell 15 by bolts (such as...). Figure 8The shell 15 is connected to the pressure detection unit. The bottom of the shell 15 has a drain port, and two opposite side walls have inlets 8 and outlets 3 that can be connected to the constant pressure and constant speed displacement unit. The other two side walls are connected to the pressure detection unit. The top of the upper cover 14 has a water inlet 13 that can be connected to the constant pressure and constant speed displacement unit. Water is injected into the confining pressure cavity 21 between the upper cover 14, the shell 15, and the porous media body 17 through the water inlet 13 to form confining pressure. In specific manufacturing, the shell is made of a high-pressure resistant visual material; the inner groove of the shell can accommodate the porous media body, and the shell and the upper cover are connected by a snap-fit ​​interlocking structure to ensure high-pressure sealing. Several bolt mounting holes 12 are provided around the upper cover 14, the porous media cover 18, and the shell 15. During assembly, bolts 19 can be sequentially passed through the bolt mounting holes on the upper cover 14, the porous media cover 18, and the shell 15, and then threaded into the nuts 20. The assembly process of the visual micro-model 6 is as follows: Figure 9 As shown.

[0054] In specific design, such as Figure 6 , 7 As shown, the mating surfaces of the porous medium body 17 and the porous medium cover plate 18 are interlocking snap-fit ​​structures 16. This snap-fit ​​structure enables a tight connection between the shell and the upper cover plate, ensuring the high-pressure sealing performance of the visualized microscopic model.

[0055] In specific embodiments of the present invention, such as Figure 1 As shown, the constant pressure and constant speed displacement unit includes a constant pressure and constant speed displacement pump 10, a pressure control system, and connecting pipelines. The constant pressure and constant speed displacement pump 10 is connected to the intermediate container 11 and the inlet 8 of the shell 15 via the connecting pipelines, and is used to inject fluid into the visualized microscopic model 6. The outlet 3 of the shell 15 is connected to the liquid collection container 4 via the connecting pipelines. The pressure control system includes a water injection pump 9 and a pressure controller 22. The water injection pump 9 is connected to the water injection port 13 on the upper cover plate 14 via the connecting pipelines (the water injection process is as follows). Figure 10 As shown in the figure, the pressure controller 22 is connected to the pressure detection unit and the water injection pump 9, and is used to monitor the confining pressure within the visualized microscopic model 6 in real time. The constant pressure and constant speed displacement pump can accurately control the injection pressure and flow rate of the displacement fluid (such as oil, water, etc.), while the pressure control system and pressure detection unit monitor the experimental displacement pressure in real time, and the confining pressure changes dynamically with the change of displacement pressure.

[0056] In the specific production process, such as Figure 2As shown, the pressure detection unit includes several pressure sensors (not shown in the figure). The pressure measuring ends 5 on the two opposite sidewalls of the housing 15 are equipped with several pressure measuring ports. Pressure sensors are installed at both the pressure measuring ports and the water inlet. These pressure sensors are all connected to the pressure controller 22, enabling them to monitor pressure changes and confining pressure changes in different areas within the housing 15. Based on the collected pressure data, the water pump is controlled to maintain the confining pressure above the displacement pressure. By installing pressure sensors at the pressure measuring ports of the housing, pressure changes in different areas within the visualized microscopic model can be monitored in real time, and pressure data can be acquired.

[0057] In specific embodiments of the present invention, such as Figure 1 As shown, the image acquisition unit includes a camera 2 and a robotic arm 23. The camera 2 is located at the end of the robotic arm 23, which drives the camera 2 to move above the visualization micro-model 6. The camera includes a high-speed camera and supporting imaging equipment. The robotic arm suspends the camera above the visualization micro-model, allowing for arbitrary adjustment of the camera position. High-resolution images of the fluid distribution and displacement process within the porous medium of the visualization micro-model are acquired for analysis of fluid interface changes and other information.

[0058] As a preferred structure, such as Figure 1 As shown, the temperature control unit 7 includes a constant temperature chamber (not shown in the figure) and a temperature controller connected to it. The visualized microscopic model 6 is located on top of the constant temperature chamber. By inputting temperature parameters into the temperature controller, the temperature of the visualized microscopic model can be adjusted to simulate the core temperature of a low-permeability tight reservoir.

[0059] To further optimize the above structure, the visualization micro-model 6 is equipped with an oleophilic semi-permeable membrane or a hydrophilic semi-permeable membrane. The oleophilic semi-permeable membrane or the hydrophilic semi-permeable membrane is set between the inlet of the shell and the porous medium body, allowing only the oil phase or the water phase to enter the porous medium body, and is used to test the pressure of the oil phase or the water phase respectively.

[0060] This invention also provides a visual experimental method for measuring dynamic capillary forces in low-permeability tight reservoirs, comprising the following steps:

[0061] Assemble the above-mentioned visualization experimental setup;

[0062] The initial parameters of the fluid injected into the constant pressure and constant speed displacement unit were set according to the experimental requirements: injection speed and injection volume.

[0063] The pressure detection unit is activated to inject water into the confining pressure chamber of the visualized micro model 6 to form confining pressure, and the confining pressure is maintained 5 MPa higher than the displacement pressure by the pressure control system.

[0064] Start the constant pressure and constant speed displacement pump 10 and sequentially inject saturated formation water and formation crude oil into the visualized micro model 6;

[0065] Restart the constant pressure and constant speed displacement pump 10 and inject displacement fluid into the visualization micro model 6 according to the set injection speed and injection volume. Monitor the pressure and flow rate of the injected fluid and the pressure of the oil phase and water phase at each pressure detection port on the visualization micro model 6, and record the experimental data. Measure the dynamic capillary force and water saturation in the porous medium body.

[0066] Stop when the injected displacement fluid reaches the set injection volume;

[0067] After the experiment, open the drain valve, remove the confining pressure, and disassemble and clean the visualization experimental device for later use.

[0068] The pressure difference between the oil phase and the water phase is the dynamic capillary force within the porous medium. The oil production and water production at the outlet on the outer shell are measured to obtain the cumulative oil production and cumulative water production.

[0069] The water saturation was obtained using the above measurement data:

[0070] Water saturation is the percentage of water in the pore space of a porous medium, and it changes continuously as the experiment progresses. Water saturation is calculated using the initial bound water saturation, influent volume, produced volume, and produced volume. Bound water saturation is the percentage of water in the pore space of the porous medium after it has been saturated with water and oil before the experiment begins. That is, the initial bound water saturation of the core (porous medium) is the percentage of water remaining in the pore space after a certain percentage of saturated oil has been introduced into the core, which was initially 100% saturated with water. Bound water saturation is a fixed value after the porous medium is fully saturated. As the water-driven oil recovery experiment progresses, the oil in the porous medium gradually decreases, while the water content gradually increases, thus changing the water saturation value within the porous medium.

[0071] For example, in a porous medium initially saturated with 100% water, if 80% saturated oil enters, the remaining 20% ​​represents the initial bound water saturation of the core. During the experiment, the amount of water entering the porous medium is equivalently inferred from the oil production at the outlet. If 10% oil is extracted, the calculated water that replaces that oil, plus the initial bound water saturation of 20%, equals the current water saturation of 30%. All percentages are by volume.

[0072] The following table shows the change of dynamic capillary force over time, obtained from the analysis of experimental data:

[0073]

[0074] The curve of dynamic capillary force changing with water saturation is as follows: Figure 11As shown, the relationship between dynamic capillary force and water saturation is as follows:

[0075]

[0076] In the formula: Fc is the dynamic capillary force;

[0077] Sw represents water saturation.

[0078] In summary, this invention, through a high-pressure resistant, visualized microscopic model paired with an adjustable-position high-speed camera, can capture the fluid distribution and displacement process within a porous medium in high definition. Simultaneously, a pressure detection unit monitors the pressure in different regions within the visualized microscopic model in real time and acquires data, achieving dual support from visualized observation and precise pressure data. This enables the analysis of the relationship between dynamic capillary force-related fluid behavior and pressure changes, solving the problems of data ambiguity or missing observations in existing methods. Furthermore, the constant-pressure, constant-rate displacement unit precisely controls the injection pressure and flow rate of the displacement fluid, making the confining pressure dynamically change with the displacement pressure. The temperature control system flexibly adjusts the experimental temperature, simulating real-world scenarios under different pressures and temperatures. This overcomes the limitations of existing methods, which rely on single experimental conditions and are difficult to adapt to complex working conditions, thus improving the scenario applicability of the measurement results.

[0079] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A visualized experimental method for measuring dynamic capillary forces in low permeability tight reservoirs, characterized in that, The method comprises the following steps: Assembling the visualization experimental device; Setting initial parameters of the fluid injection according to experimental requirements: injection rate and injection volume; Starting the pressure detection unit to inject water into the confining pressure cavity of the visualization microcosmic model to form confining pressure, and keeping the confining pressure higher than the displacement pressure by 5 MPa; Starting the constant pressure and constant speed displacement pump of the constant pressure and constant speed displacement unit to sequentially inject saturated formation water and formation crude oil into the visualization microcosmic model; Starting the constant pressure and constant speed displacement pump again to inject displacement fluid into the visualization microcosmic model according to the set injection rate and injection volume, and monitoring the pressure, flow rate of the injected fluid, and the pressure of the oil phase and water phase at each pressure detection port of the visualization microcosmic model, and recording experimental data; Measuring the dynamic capillary force and water saturation in the porous medium body; The pressure difference between the oil phase and the water phase is the dynamic capillary force in the porous medium body, the oil production and water production at the outlet of the shell are measured to obtain the cumulative oil production and cumulative water production, and the water saturation is measured; The relationship between the dynamic capillary force and the water saturation is as follows: In the formula: Fc is dynamic capillary force; Sw is water saturation; stop when the injection of displacement fluid reaches the set injection amount; after the experiment ends, open the drainage valve, unload the confining pressure, disassemble and clean the visualization experiment device for standby; the visualization experiment device comprises a visualization microcosmic model, a constant-pressure constant-speed displacement unit, a pressure detection unit, an image acquisition unit, a temperature control unit and a computer, the visualization microcosmic model comprises a transparent shell and a porous medium body in the shell, and an intermediate region between the shell and the porous medium body can be filled with water to form a confining pressure; The constant pressure and constant speed displacement unit is connected with the visualization microcosmic model, and is used for injecting fluid into the visualization microcosmic model; the pressure detection unit is used for detecting the pressure at different positions of the visualization microcosmic model; the image acquisition unit is used for acquiring images of the fluid distribution and displacement process in the visualization microcosmic model; and the temperature control unit is used for controlling the temperature of the visualization microcosmic model; the constant pressure and constant speed displacement unit, the pressure detection unit, the image acquisition unit, and the temperature control unit are all connected with the computer; The shell comprises a shell body with an open top, a porous medium cover plate at the top of the shell body, and an upper cover plate; the porous medium cover plate is arranged at the top of the porous medium body and is clamped and matched with the four edges thereof; the porous medium body and the porous medium cover plate are arranged in the shell body; and the upper cover plate is arranged at the top of the shell body, and the edges of the upper cover plate are connected with the four side walls of the shell body through a bolt pair. The matching surfaces of the four edges of the porous medium body and the porous medium cover plate are clamping structures with concave-convex engagement; the shell is made of a high-pressure visualization material; the groove in the shell body can accommodate the porous medium body; and the shell and the upper cover plate are clamped and matched through an inlay structure to ensure high-pressure sealing.

2. The visualized experimental method for measuring dynamic capillary forces in low permeability tight reservoirs according to claim 1, characterized in that: The bottom of the shell body is provided with a liquid discharge port, the opposite two side walls are respectively provided with an inlet and an outlet that can be connected with the constant pressure and constant speed displacement unit, and the other two side walls are connected with the pressure detection unit; the top of the upper cover plate is provided with a water injection port that can be connected with the constant pressure and constant speed displacement unit, and water is injected into the confining pressure cavity between the upper cover plate, the shell body, and the porous medium body through the water injection port to form confining pressure.

3. The visualized experimental method for measuring dynamic capillary forces in low permeability tight reservoirs according to claim 2, characterized in that: The constant pressure and constant speed displacement unit comprises a constant pressure and constant speed displacement pump, a pressure control system, and connecting pipelines; the constant pressure and constant speed displacement pump is connected with an intermediate container and the inlet of the shell body through the connecting pipelines, and is used for injecting fluid into the visualization microcosmic model; the outlet of the shell body is connected with a liquid collection container through the connecting pipelines; the pressure control system comprises a water injection pump and a pressure controller; the water injection pump is connected with the water injection port on the upper cover plate through the connecting pipelines; and the pressure controller is connected with the pressure detection unit and the water injection pump, and is used for monitoring the confining pressure in the visualization microcosmic model in real time.

4. The visualized experimental method for measuring dynamic capillary forces in low permeability tight reservoirs according to claim 3, characterized in that: The pressure detection unit comprises a plurality of pressure sensors, a plurality of pressure measuring ports are arranged on two opposite side walls of the shell for mounting the pressure sensors; the pressure sensors are connected with a pressure controller for monitoring pressure changes in different areas in the shell and collecting pressure data.

5. The visualized experimental method for measuring dynamic capillary forces in low permeability tight reservoirs of claim 1, wherein: The image acquisition unit comprises a camera and a mechanical arm, the camera is arranged at the end of the mechanical arm, and the mechanical arm is used for driving the camera to move above the visual micro model.

6. The visualized experimental method for measuring dynamic capillary forces in low permeability tight reservoirs of claim 1, wherein: The temperature control unit comprises a thermostat and a temperature controller connected therewith, and the visual micro model is arranged at the top of the thermostat.

7. The visualized experimental method for measuring dynamic capillary forces in low permeability tight reservoirs of claim 1, wherein: An oleophilic semi-permeable membrane or a hydrophilic semi-permeable membrane is arranged in the visual micro model, the oleophilic semi-permeable membrane or the hydrophilic semi-permeable membrane is arranged between the inlet of the shell and the porous medium body, and only the oil phase or the water phase enters the porous medium body, which is used for testing the pressure of the oil phase or the water phase.

Images