A high-temperature and high-pressure sandstone erosion microscopic visualization experiment method

Abstract

This invention relates to a microscopic visualization experimental method for high-temperature and high-pressure sandstone erosion. The method includes: preparing a high-temperature and high-pressure resistant microfluidic chip that can be embedded in real sandstone thin sections; considering the real-time microscopic visualization of the erosion process under high-temperature and high-pressure conditions in a real geological environment; and considering the influence of different injection pressures and flow rates on particle shedding. This invention can provide important erosion-related parameters for numerical simulation, such as critical erosion velocity, pressure, and temperature, and solves the problem of microscopic quantitative characterization of sandstone pore structure changes during erosion.

Description

Technical Field

[0001] This invention relates to the field of sandstone reservoir development technology. In particular, it relates to a microscopic visualization experimental method for high-temperature, high-pressure sandstone erosion. Background Technology

[0002] Water injection is one of the main methods for developing sandstone reservoirs in my country. With increasing development time, sandstone reservoirs generally enter the medium-to-high water-cut stage. During long-term water injection development, sandstone reservoirs undergo prolonged water erosion, weakening the cementation of the framework particles and causing some particles to detach, leading to pore enlargement or pore reduction due to blockage by transported particles. These changes in pore structure significantly affect the subsurface multiphase flow process. Related research is a crucial foundation for understanding development patterns and adjusting development strategies, thus holding significant importance in the field of oilfield development engineering.

[0003] Existing numerical simulation methods can design models based on parameters of different sandstone types, enabling visualization and quantitative description of changes in pore structure and particle flow patterns after continuous erosion and subsequent particle detachment. They also allow for repeatable, batch-based multi-factor sensitivity analysis. However, numerical simulation methods make numerous assumptions, making it difficult to cover the complexity of real-world conditions. Some key parameters, such as critical shear force, critical erosion rate, and pressure, still require verification through real physical experiments.

[0004] Current physical experimental methods typically rely on macroscopic columnar cores. Sandstone cores are placed in core holders and subjected to water flushing. After the experiment, linear CT scans are used to acquire pore-scale images at various time points, comparing the loss of framework particles and changes in pore structure before and after the experiment. However, this method is difficult, has low repeatability, is costly, and lacks visualization and quantification of the microscopic flushing process. Especially under high temperature and pressure, the physical mechanisms such as rock cementation strength and microparticle migration behavior are complex and difficult to observe directly. Furthermore, the evolution of pore structure caused by flushing significantly affects seepage characteristics, but the lack of refined dynamic observation techniques limits a deeper understanding of the flushing process mechanism.

[0005] How to address the shortcomings of existing technologies in considering the long-term erosion of sandstone particles and the time-varying nature of pore structure under real high-temperature and high-pressure conditions is an urgent problem to be solved. Summary of the Invention

[0006] This invention provides a microscopic visualization experimental method for high-temperature and high-pressure sandstone erosion, which addresses the shortcomings of existing technologies in considering the dynamic laws governing particle detachment and migration and the time-varying pore structure of sandstone after long-term erosion under real high-temperature and high-pressure conditions.

[0007] To achieve the above objectives, in a first aspect, the present invention relates to a microscopic visualization experimental method for high-temperature and high-pressure sandstone erosion, comprising:

[0008] Design and fabricate microfluidic chips;

[0009] The intermediate container is filled with the experimental injection fluid for later use, and then the model loading and injection process is carried out.

[0010] First, open the lid of the high-temperature and high-pressure visual reactor. Place the microfluidic chip, embedded with a real rock sample, into the pre-cut groove in the high-temperature and high-pressure visual reactor, and use the built-in threaded retainer to fix the microfluidic chip. The rubber of the retainer will seal the injection and output ports of the microfluidic chip and the injection and output pipeline to prevent leakage. After fixing the microfluidic chip, tighten the lid, the internal temperature sensor, pressure sensor, and the pressure control knob.

[0011] Turn on the LED light and aim the light head at the sapphire area at the bottom of the reactor; align the Leica Z16APO microscopic visualization system of the high-temperature and high-pressure visual reactor with the sapphire observation area on the upper side of the reactor, adjust the focus and position of the microscope head, and at the same time check the video observation area of ​​the high-temperature and high-pressure experimental area to ensure that the microfluidic chip is placed in the center of the field of view and the sample edge is clear;

[0012] Once the temperature is set to a specific temperature, the external heating device will gradually raise the temperature to the specific temperature and transmit the heat to the microfluidic chip inside the reactor.

[0013] Turn on the power to the pressure control room of the high-temperature and high-pressure experimental zone and start the pressure control system; in the equipment software operation area of ​​the high-temperature and high-pressure experimental zone, set the confining pressure to constant pressure mode, with a pressure of 2 MPa, and click start. The confining pressure pump will inject deionized water into the reactor. At the same time, pay attention to the confining pressure value displayed on the software and the situation inside the reactor in the video observation area of ​​the high-temperature and high-pressure experimental zone; when the confining pressure reaches 2 MPa, there are no bubbles in the reactor initially and the edges are clear;

[0014] Set the confining pressure to tracking mode with a pressure difference of 2 MPa. The confining pressure will automatically increase as the injection pressure rises and automatically decrease as the injection pressure falls. The pressure difference is the set value.

[0015] Start injecting fluid by setting the injection to constant flow mode and monitoring the inlet pressure change. Then turn on the back pressure system and set it to constant pressure mode at 3 MPa. If it is an atmospheric pressure experiment, there is no need to turn on the back pressure system and keep the injection pressure below 1 MPa.

[0016] Pay attention to the inlet pressure. The injected fluid will be affected by the outlet back pressure and will rise to a pressure slightly higher than the back pressure to ensure fluid outflow. Setting the back pressure to constant pressure mode will help control the pressure inside the vessel and maintain it at the specific system pressure required for the experiment. Gradually increase the back pressure value by 1 MPa per interval to allow the injection pressure to steadily rise to a high pressure.

[0017] The experiment was conducted under a high temperature and high pressure environment, and the sandstone erosion process under different flow velocities and pressures was recorded in real time through the video observation area of ​​the high temperature and high pressure experimental zone.

[0018] After the experiment is completed, stop the injection and set the confining pressure and back pressure to 0. After the confining pressure and back pressure drop to 0, unscrew the confining pressure valve on the high-temperature and high-pressure visual reactor to release the residual pressure. Only after water vapor stops flowing out can the high-temperature and high-pressure visual reactor be opened.

[0019] Preferably, the design and fabrication of the microfluidic chip specifically includes:

[0020] Schott B270 glass material was selected as the substrate and cover plate of the microfluidic chip; the substrate and the cover plate have the same size, with a length and width of 4cm and a thickness of 2mm; the substrate glass was etched with hydrofluoric acid to form the flow channel, which has a width of 1mm and is connected to the observation area, which has a length of 4mm and a width of 4mm. The flow channel is connected to the observation area and has a depth of 1mm.

[0021] The sandstone sample was first wire-cut to a size of 4mm long, 4mm wide, and 1.5mm thick, and then the sandstone thin slice was ground to a thickness of 0.95mm using a grinding table; a polydimethylsiloxane material with a size of 3.5mm long, 3.5mm wide, and 0.025mm thick was wrapped around the rock thin slice for later use.

[0022] The substrate was cleaned sequentially with isopropanol, ethanol, and deionized water, wiped clean with lint-free paper, and the sandstone thin section was embedded into the groove of the observation area and pressed firmly against the inner wall with tweezers.

[0023] The substrate and another polydimethylsiloxane film (5cm long, 5mm wide, and 0.1mm thick) were simultaneously placed in a plasma cleaner for plasma cleaning. After cleaning, the cleaned side of the polydimethylsiloxane film was aligned with the cleaned side of the substrate and pressure bonded. The treated glass surface and the silicon groups in the polydimethylsiloxane formed covalent bonds, generating silicon-oxygen-silicon bonds, achieving a strong connection. The bonded model was then placed in a 70°C oven for 30 minutes for further deep bonding.

[0024] After 30 minutes, remove the model and use a 2mm diameter punch to remove the polydimethylsiloxane at the inlet and outlet.

[0025] Clean the other glass cover in sequence with isopropanol, ethanol, and deionized water, and wipe it clean with lint-free paper.

[0026] Peel off the protective film from the other side of the polydimethylsiloxane film and place it in a plasma cleaner along with the glass cover for plasma cleaning. After cleaning, align the cleaned side of the polydimethylsiloxane film with the cleaned side of the glass cover and perform pressure bonding. Place the bonded model in a 70-degree Celsius oven for 30 minutes for further deep bonding.

[0027] After removing the bonded model and cutting off a 1mm wide strip of polydimethylsiloxane around its perimeter, the microfluidic chip is obtained.

[0028] Preferably, the pre-carved groove has a size of 4cm×4cm×4mm.

[0029] The present invention relates to a microscopic visualization experimental method for high-temperature and high-pressure sandstone erosion, which has the following advantages compared with the prior art:

[0030] This invention combines a microfluidic chip, a temperature and pressure control device, and an imaging system to achieve high-resolution real-time tracking of particle shedding, migration, and redeposition processes.

[0031] This invention considers a physical simulation method for studying the erosion evolution of sandstone pore structure under high temperature and pressure. Its key feature is the use of a high-temperature and high-pressure resistant microfluidic chip that can be embedded in real sandstone thin sections. Utilizing a high-temperature and high-pressure microscopic visualization experimental platform, it simulates the actual temperature and pressure environment of the formation, while simultaneously observing the sandstone erosion process in real time, providing crucial erosion-related parameters (critical erosion velocity, pressure, temperature, etc.) for numerical simulation. The advantage of this invention lies in its ability to precisely control relatively high temperatures (25-200℃) and relatively high system pressures (0-70 MPa), ensuring that the chip is not damaged and the images remain clear, while completing microscopic sandstone erosion experiments with different injection parameters. This is currently a unique experimental procedure and yields results. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating a microscopic visualization experimental method for high-temperature and high-pressure sandstone erosion in Example 1.

[0033] Figure 2 A schematic diagram of the high-temperature and high-pressure equipment structure for a microscopic visualization experimental method of high-temperature and high-pressure sandstone erosion in Example 1.

[0034] Figure 3 Example 1 shows a microscopic visualization experiment method for high-temperature and high-pressure sandstone erosion, including the construction of channels with different structures under a microscope and the initial state of the sandstone before erosion during the experiment.

[0035] Figure 4Schematic diagrams of two CAD-designed scour models for a microscopic visualization experimental method for high-temperature and high-pressure sandstone scour in Embodiment 1 of the present invention;

[0036] Figure 5 A schematic diagram of the intermediate channel scouring process in Example 1 of a microscopic visualization experimental method for high-temperature and high-pressure sandstone scouring according to Embodiment 1 of the present invention.

[0037] Figure 6 A schematic diagram of the upper channel scouring process in Example 1 of a microscopic visualization experimental method for high-temperature and high-pressure sandstone scouring according to Embodiment 1 of the present invention.

[0038] Figure 7 A schematic diagram of the numerical simulation comparison and verification process of upper channel scour in Example 2 of the microscopic visualization experimental method for high temperature and high pressure sandstone scour in Embodiment 1 of the present invention. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention and not the entire structure.

[0040] Example 1

[0041] A microscopic visualization experimental method for high-temperature and high-pressure sandstone erosion; please refer to [link / reference]. Figure 1-6 As shown, the present invention provides a microscopic visualization experimental method for high-temperature and high-pressure sandstone erosion, and identification of the flow state of heat flow signals on the wall of a hypersonic wind tunnel, comprising the following steps: S101 to S111.

[0042] S101 designed and fabricated microfluidic chips;

[0043] S102 fills the intermediate container with the experimental injection fluid for later use, and then proceeds with the model loading and injection process;

[0044] S103 First, open the lid of the high-temperature and high-pressure visual reactor. Place the microfluidic chip embedded with the real rock sample into the pre-cut 4cm×4cm×4mm groove in the high-temperature and high-pressure visual reactor, and use the built-in threaded retainer to fix the microfluidic chip. The rubber of the retainer will seal the injection and output ports of the microfluidic chip and the injection and output pipeline to prevent leakage. After fixing the microfluidic chip, tighten the lid, the internal temperature sensor, pressure sensor and the pressure control knob.

[0045] S104 Turn on the LED light and aim the light head at the sapphire area at the bottom of the reactor; aim the Leica Z16 APO microscopic visualization system of the high-temperature and high-pressure visual reactor at the sapphire observation area on the upper side of the reactor, adjust the focus and position of the microscope head, and at the same time check the video observation area of ​​the high-temperature and high-pressure experimental area to ensure that the microfluidic chip is placed in the center of the field of view and the sample edge is clear.

[0046] S105 sets the temperature to a specific temperature, and the external heating device will gradually heat up to the specific temperature and transmit the temperature to the microfluidic chip inside the vessel.

[0047] S106 Turn on the power to the pressure control room of the high-temperature and high-pressure experimental zone and start the pressure control system; In the equipment software operation area of ​​the high-temperature and high-pressure experimental zone, set the confining pressure to constant pressure mode, with a pressure of 2 MPa, and click start. The confining pressure pump will inject deionized water into the reactor. At the same time, pay attention to the confining pressure value displayed on the software and the situation inside the reactor in the video observation area of ​​the high-temperature and high-pressure experimental zone; When the confining pressure reaches 2 MPa, there are no bubbles in the reactor initially and the edges are clear;

[0048] In this embodiment, activating the pressure control system specifically includes: starting the air compressor, driving the plunger pump, and controlling the pressure by injecting water into the vessel.

[0049] S107 sets the confining pressure to tracking mode with a pressure difference of 2 MPa. The confining pressure will automatically increase as the injection pressure increases and automatically decrease as the injection pressure decreases. The pressure difference is the set value.

[0050] S108 sets the injection to constant flow mode and starts injecting fluid while monitoring inlet pressure changes. Then, it turns on the back pressure system and sets the back pressure to constant pressure mode at 3 MPa. If it is an atmospheric pressure experiment, the back pressure system does not need to be turned on, and the injection pressure is always kept below 1 MPa.

[0051] In this embodiment, the back pressure pump is started, the back pressure system is turned on, and water is injected into the back pressure device. If the injection pressure exceeds the back pressure system pressure, the water can flow through. The back pressure is set to constant pressure mode with a pressure of 3 MPa. At this time, the injection pressure needs to exceed 3 MPa.

[0052] S109 focuses on the inlet pressure. The injected fluid is affected by the outlet back pressure, which will rise to a pressure slightly higher than the back pressure to ensure fluid outflow. Setting the back pressure to constant pressure mode will help control the pressure inside the vessel and maintain it at the experimental system pressure. Gradually increase the back pressure value by 1 MPa per interval to make the injection pressure rise steadily to high pressure; otherwise, it will cause the model to rupture.

[0053] The S110 experiment conducted real-time dynamic visualization observation under high temperature and high pressure environment. The sandstone erosion process under different flow rates and pressures was recorded in real time through the video observation area of ​​the high temperature and high pressure experimental area.

[0054] After the S111 experiment is completed, stop the injection, set the confining pressure and back pressure to 0, and wait for the confining pressure and back pressure to drop to 0. Then, unscrew the confining pressure valve on the high-temperature and high-pressure visual reactor to release the residual pressure. Only after water vapor stops flowing out can the high-temperature and high-pressure visual reactor be opened.

[0055] like Figure 2 In the diagram, ①a) video observation area; b) equipment software operation area; c) ISCO pressure plunger pump; d) pressure control chamber; e) LED light source; f) high-temperature and high-pressure reactor; where a, b, c, d, and f are connected, b is the main control interface, controlling a for video observation and controlling c and d to activate the pressure system feedback to f; e is activated independently to provide a transmitted light source for f. ②a) Leica Z16 APO microscopic visualization system (with camera). ③a) Example of a microfluidic chip embedded with a real rock sample. ②a is placed directly above the central window of ①f; focus to observe the specific dynamic processes of the rock in the chip in ③a. Figure 2 The document showcases the components of a high-temperature and high-pressure equipment system and the physical characteristics of a microfluidic chip.

[0056] Figure 3 In the middle, a) fluid channels; b) real sandstone. Figure 3 The diagram shows the channel structures with different features under a microscope and the initial state of sandstone before erosion in the experiment. The fluid flows through points a and b, where erosion and other interactions occur, which are observed and recorded in real time via point ②a.

[0057] In this embodiment, S101 specifically includes S1011 to S1018.

[0058] S1011 uses Schott B270 glass as the substrate and cover plate of the microfluidic chip; the substrate and the cover plate have the same size, with a length and width of 4cm and a thickness of 2mm; the substrate glass is etched with hydrofluoric acid to form the flow channel, which is 1mm wide and has a size of 4mm long and 4mm wide to connect with the observation area, with a depth of 1mm.

[0059] S1012 first used wire cutting to cut the sandstone sample to a size of 4mm long, 4mm wide, and 1.5mm thick, and then used a grinding table to grind the sandstone thin slice to a thickness of 0.95mm; then used polydimethylsiloxane with a size of 3.5mm long, 3.5mm wide, and 0.025mm thick to wrap around the rock thin slice for later use.

[0060] S1013 used isopropanol, ethanol, and deionized water to clean the substrate in sequence, wiped it clean with lint-free paper, and embedded the sandstone thin section into the groove of the observation area, pressing it firmly against the inner wall with tweezers.

[0061] S1014 involves simultaneously placing the substrate and another 5cm long, 5mm wide, and 0.1mm thick polydimethylsiloxane film into a plasma cleaner for plasma cleaning. After cleaning, the cleaned side of the polydimethylsiloxane film is aligned with the cleaned side of the substrate and pressure bonded. The treated glass surface covalently bonds with the silicon groups in the polydimethylsiloxane, forming silicon-oxygen-silicon bonds for a strong connection. The bonded model is then placed in a 70°C oven for 30 minutes for further deep bonding.

[0062] S1015: After 30 minutes, take out the model and use a 2mm diameter punch to remove the polydimethylsiloxane at the inlet and outlet.

[0063] S1016 uses isopropanol, ethanol, and deionized water to clean the other glass cover in sequence, and then wipes it clean with lint-free paper.

[0064] S1017 peels off the protective film on the other side of another polydimethylsiloxane film and puts it into a plasma cleaner along with the glass cover for plasma cleaning. After cleaning, the cleaned side of the polydimethylsiloxane film is aligned with the cleaned side of the glass cover and pressure bonded. The bonded model is then placed in a 70-degree oven for 30 minutes for further deep bonding.

[0065] S1018 Removes the bonded model, cuts off a 1mm wide polydimethylsiloxane border, and obtains the microfluidic chip.

[0066] To further illustrate the present invention, two embodiments are provided: one is a middle flow channel flushing mode, and the other is an upper flow channel flushing mode (e.g., ...). Figure 4 As shown, in Figure 4 In the image, the left side represents the middle flow channel flushing mode; the right side represents the upper flow channel flushing mode. Figure 4 Two CAD-designed flushing models are shown (including the flow channels and visible areas). In both the middle flow channel flushing mode and the upper flow channel flushing mode, fluid is injected from two inlets and flows out from one outlet, ensuring a stable and efficient flushing process.

[0067] Example 1:

[0068] like Figure 5-6 As shown, Figure 5 The image shows the microscopic scouring process and particle shedding effect in the intermediate flow channel mode. Figure 6 The image shows the microscopic scouring process and particle shedding effect in the upper channel mode.

[0069] Intermediate Channel Mode: Example 1 used sandstone from the Shaximiao Formation in Sichuan Province; injection flow rate: 20 mL / min; pressure: 20 MPa; confining pressure: 20 MPa; temperature: 100℃. In the intermediate channel mode, water was injected from the middle channel at the bottom of the model, passed through the intermediate scouring zone, and flowed out from the upper middle channel. Initially, there was no particle migration. As the scouring time increased, the process involved the ejection of fine particles, the ejection of coarse particles, the detachment of coarse particles, and the disintegration of the sandstone's porous cementation structure. Complete observation records were kept of the particle detachment state and process of sandstone under continuous scouring at each time point.

[0070] Example 2:

[0071] Upper channel mode: Example 2 used sandstone from the Shaximiao Formation in Sichuan Province; injection flow rate: 20 mL / min; injection pressure: 20 MPa; confining pressure: 20 MPa; temperature: 100℃. In the upper channel mode, water was injected from the upper left channel of the model, passed through the middle scouring zone, and flowed out from the upper right channel. Initially, there was no particle migration. As the scouring time increased, it went through steps such as coarse particle flushing and detachment. Complete observation records were made of the particle detachment state and process of sandstone under continuous scouring at each time point. Then, by coupling the particle scouring and detachment experiment with a high-temperature and high-pressure visualization experimental device and high-precision CFD simulation, the dynamic capture and critical threshold quantification of the local shear stress at the moment of particle detachment were realized, and the critical pressure and flow rate of particle detachment and the detachment location (e.g., Figure 7 As shown, this demonstrates the effect of coupling microscopic shedding physics experiments with high-precision CFD simulation.

[0072] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0073] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A microscopic visualization experimental method for high-temperature and high-pressure sandstone erosion, characterized in that, include: Design and fabricate microfluidic chips; The intermediate container is filled with the experimental injection fluid for later use, and then the model loading and injection process is carried out. First, open the lid of the high-temperature and high-pressure visual reactor, place the microfluidic chip embedded with the real rock sample into the pre-cut groove of the high-temperature and high-pressure visual reactor, and fix the microfluidic chip with the built-in threaded retainer; after fixing the microfluidic chip, tighten the lid, the internal temperature sensor, the pressure sensor, and the confining pressure knob. Turn on the LED light and aim the light head at the sapphire area at the bottom of the reactor; align the Leica Z16 APO microscopic visualization system of the high-temperature and high-pressure visual reactor with the sapphire observation area on the upper side of the reactor, adjust the focus and position of the microscope head, and at the same time check the video observation area of ​​the high-temperature and high-pressure experimental area to ensure that the microfluidic chip is placed in the center of the field of view and the sample edge is clear; Once the temperature is set to a specific temperature, the external heating device will gradually raise the temperature to the specific temperature and transmit the heat to the microfluidic chip inside the reactor. Turn on the power to the pressure control room of the high-temperature and high-pressure experimental zone and start the pressure control system; in the equipment software operation area of ​​the high-temperature and high-pressure experimental zone, set the confining pressure to constant pressure mode, with a pressure of 2 MPa, and click start. The confining pressure pump will inject deionized water into the reactor. At the same time, pay attention to the confining pressure value displayed on the software and the situation inside the reactor in the video observation area of ​​the high-temperature and high-pressure experimental zone; when the confining pressure reaches 2 MPa, there are no bubbles in the reactor initially and the edges are clear; Set the confining pressure to tracking mode with a pressure difference of 2 MPa. The confining pressure will automatically increase as the injection pressure rises and automatically decrease as the injection pressure falls. The pressure difference is the set value. Start injecting fluid by setting the injection to constant flow mode and monitoring the inlet pressure change. Then turn on the back pressure system and set it to constant pressure mode at 3 MPa. If it is an atmospheric pressure experiment, there is no need to turn on the back pressure system and keep the injection pressure below 1 MPa. Pay attention to the inlet pressure. The injected fluid will be affected by the outlet back pressure and will rise to a pressure higher than the back pressure to ensure fluid outflow. Setting the back pressure to constant pressure mode will help control the pressure inside the vessel and maintain it at the specific system pressure required for the experiment. Gradually increase the back pressure value by 1 MPa per interval to allow the injection pressure to steadily rise to a high pressure. The experiment was conducted under high temperature and high pressure conditions, and real-time dynamic visualization observation was carried out. The sandstone erosion process under different flow velocities and pressures was recorded in real time through the video observation area of ​​the high temperature and high pressure experimental zone.

2. The experimental method for microscopic visualization of high-temperature and high-pressure sandstone erosion according to claim 1, characterized in that, After the experiment is completed, the following steps are also taken: stop the injection, set the confining pressure and back pressure to 0, and after the confining pressure and back pressure drop to 0, unscrew the confining pressure valve on the high-temperature and high-pressure visual reactor to release the residual pressure. Only after water vapor stops flowing out can the high-temperature and high-pressure visual reactor be opened.

3. The experimental method for microscopic visualization of high-temperature and high-pressure sandstone erosion according to claim 1, characterized in that, The design and fabrication of the microfluidic chip specifically includes: Schott B270 glass material was selected as the substrate and cover plate of the microfluidic chip; the substrate and the cover plate have the same size, with a length and width of 4cm and a thickness of 2mm; the substrate glass was etched with hydrofluoric acid to form the flow channel, which has a width of 1mm and is connected to the observation area, which has a length of 4mm and a width of 4mm. The flow channel is connected to the observation area and has a depth of 1mm. The sandstone sample was first wire-cut to a size of 4mm long, 4mm wide, and 1.5mm thick, and then the sandstone thin slice was ground to a thickness of 0.95mm using a grinding table; a polydimethylsiloxane material with a size of 3.5mm long, 3.5mm wide, and 0.025mm thick was wrapped around the rock thin slice for later use. The substrate was cleaned sequentially with isopropanol, ethanol, and deionized water, wiped clean with lint-free paper, and the sandstone thin section was embedded into the groove of the observation area and pressed firmly against the inner wall with tweezers. The substrate and another polydimethylsiloxane film (5cm long, 5mm wide, and 0.1mm thick) were simultaneously placed in a plasma cleaner for plasma cleaning. After cleaning, the cleaned side of the polydimethylsiloxane film was aligned with the cleaned side of the substrate and pressure bonded. The treated glass surface and the silicon groups in the polydimethylsiloxane formed covalent bonds, generating silicon-oxygen-silicon bonds, achieving a strong connection. The bonded model was then placed in a 70°C oven for 30 minutes for further deep bonding. After 30 minutes, remove the model and use a 2mm diameter punch to remove the polydimethylsiloxane at the inlet and outlet. Clean the other glass cover in sequence with isopropanol, ethanol, and deionized water, and wipe it clean with lint-free paper. Peel off the protective film from the other side of the polydimethylsiloxane film and place it in a plasma cleaner along with the glass cover for plasma cleaning. After cleaning, align the cleaned side of the polydimethylsiloxane film with the cleaned side of the glass cover and perform pressure bonding. Place the bonded model in a 70-degree Celsius oven for 30 minutes for further deep bonding. After removing the bonded model and cutting off a 1mm wide strip of polydimethylsiloxane around its perimeter, the microfluidic chip is obtained.

4. The experimental method for microscopic visualization of high-temperature and high-pressure sandstone erosion according to claim 1, characterized in that, The pre-carved groove measures 4cm × 4cm × 4mm.

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