Microfluid model for rock seepage corrosion-deformation visualization experiment, preparation method and test method

Abstract

The invention discloses a microfluid model for a rock seepage corrosion-deformation visualization experiment and a test method thereof. The microfluid model comprises a transparent interface model unit, a circulating fluid supply unit, an automatic switching valve group and an effluent collecting and monitoring unit. The transparent interface model unit forms an interlayer space by upper and lower transparent plates; the circulating fluid supply unit comprises an acid corrosion liquid storage tank and a clear water storage tank; the automatic switching valve group periodically switches the flow path; the effluent monitoring unit collects ion concentration, particle content and seepage parameters in real time. The permeability evolution is inversed by monitoring the pressure difference change, the corrosion rate and the scouring falling amount are calculated in combination with waste liquid analysis, and an accumulated degradation index and a failure threshold value are introduced to realize intelligent judgment. According to the method, the chemical-hydraulic coupling effect in the underground environment can be truly reproduced, the interface degradation mechanism is visually revealed, the long-term durability of the grouting interface is quantitatively evaluated, and a scientific basis is provided for grouting material optimization, mix proportion optimization and engineering life prediction.

Description

Technical Field

[0001] This invention relates to the field of geological science and engineering technology, and in particular to a microfluidic model, preparation method, and testing method for visualizing rock seepage, dissolution, and deformation experiments. Background Technology

[0002] The seepage-erosion process in fractured rock masses is closely related to a series of processes such as oil and gas extraction, carbon dioxide geological storage, and contaminant transport. The permeability of fractured rock masses determines the efficiency of oil and gas extraction, the safety of geological storage, and the dominant pathway for contaminant transport. The permeability of fractured media mainly depends on the geometry of the rock mass. In engineering practice, such as in carbon dioxide geological storage, the geometry of fractures is affected by two factors: first, the seepage and dissolution process of the fractured media causes the rock mass fractures to expand, increasing the rock mass permeability; second, under real conditions, the rock mass is subjected to stress, leading to fracture closure and reducing the rock mass permeability. However, the competitive mechanism and macroscopic impact of stress closure and dissolution expansion are still unclear. Visualization experiments are an important means to reveal the microscopic mechanism of seepage-erosion in fractured rocks. Using visualization experiments, the evolution of the geometric structure of rock fractures under the coupling of seepage, dissolution, and stress, as well as the seepage process within the fractures, can be observed, helping to reveal the microscopic mechanism of seepage-stress-erosion in fractured media.

[0003] Currently, the following research methods are mainly used to study the coupled processes of deformation and seepage / dissolution in real rock fractures:

[0004] (1) High-power transmission technologies such as CT, X-ray, and nuclear magnetic resonance are used to observe the internal spatial geometry or fluid seepage channels of real rock fractures. The main principle is to use the different attenuation of high-energy electromagnetic wave signals between the rock skeleton, fluid, and pores to distinguish the targets of the rock skeleton, fluid, and pores. Its advantage is that it can directly observe the seepage process inside real rocks and the changes in rock pore structure induced by erosion. It is an in-situ testing technology that can observe the evolution of fracture geometry under the combined action of deformation and seepage dissolution. Its disadvantage is that it is difficult to balance imaging speed and observation field of view. The fastest reconstruction rate of standard rock core images (at which the resolution is low, mm level) still takes about 15 minutes. It is difficult to capture the rapid flow process (ms level) in the fractured medium. Moreover, the cost of experimental equipment such as CT is high and the amount of calculation required for data interpretation is large.

[0005] (2) Real-time dynamic observation of the spatial geometry of rock fissures based on optical transmission method. This method combines optical transmission technology and Beer-Lambert's law to dynamically capture the evolution of the geometric structure of the seepage and dissolution process inside rock fissures. The principle is to calculate the fissure opening by inversely calculating the light transmission intensity of the dyed fluid. Its advantage is that the reconstruction speed is fast, and it can almost realize real-time observation of the flow and spatial structure inside the fissure (frame rate ~ms). The relevant details have been disclosed in the patent document CN117741107A, "A Device and Method for Visualizing the Coupling Mechanism of Seepage-Dissolution in Rock Fractals". Its disadvantage is that transparent materials (such as sodium chloride) must be used to simulate the fissure model, which makes it difficult to reflect the chemical parameters of the rock (real mineral content, mineral distribution).

[0006] (3) Microfluidic models embedded with real geological materials. By embedding real geological materials in a polydimethylsiloxane (PDMS) cavity mold, the seepage and dissolution process of real rocks (such as limestone, salt rock, sandstone and other common soluble rocks, not limited to transparent pure minerals) can be simulated, thus breaking free from the limitations of ideal transparent materials and revealing the influence of geochemical reactions on the fracture seepage and dissolution process. The fabrication of related models has been disclosed in patent documents such as CN202411075399.X Quantitative Methods and Devices for Chemical and Physical Erosion of Rocks and CN201910238487.X Microfluidic Chips and Fabrication Methods for the Study of Chemical Dissolution in Geological Processes.

[0007] Currently, there are a series of mature methods for model preparation and experimental research on the microscopic mechanism of rock seepage and dissolution processes, such as the aforementioned microfluidic models embedded with real geological materials and the real-time dynamic observation method of rock fracture spatial geometry based on optical transmission methods. However, real rock masses are often located in deep strata and are also subject to fracture deformation and closure caused by stress. There is a complex interaction between seepage and dissolution and deformation. Existing experimental setups that only simulate the seepage and dissolution process are insufficient to reveal the interaction mechanism between seepage and dissolution and deformation in deep rock masses. The main challenges in visualizing the seepage and dissolution-deformation process inside fractured media under the combined action of stress and seepage and dissolution in real rock fractures are reflected in the following two aspects: (1) Incompatibility between stress application equipment and visualization observation equipment in terms of spatial arrangement. For the light transmission method, in addition to using transparent materials as the research object, the observation of the seepage and dissolution process also requires setting up a light source below the model and a high-speed camera above it. The stress device also needs to be arranged in the same position, which leads to a contradiction that is difficult to coordinate between the two.

[0008] (2) Spatial limitations of traditional microfluidic models. The fabrication of microfluidic models is economical, rapid, and highly repeatable. Traditional microfluidic models can achieve dynamic observation of the real rock seepage and dissolution process by simply embedding the object to be observed into the microfluidic model by designing a specific cavity structure. However, due to the constraints of internal space, it is difficult to add additional stress application devices inside the chip, thus making it difficult to simulate the effect of stress.

[0009] To maximize the representation of the physicochemical effects of different minerals in real rocks under stress, this application proposes a microfluidic model, preparation method, and experimental method for visualizing rock seepage dissolution-deformation experiments.

[0010] The aim is to improve existing microfluidic modeling techniques and establish a new microfluidic model preparation technique that can realize stress loading and fracture deformation, thereby enabling the visualization and observation of the coupled process of real rock deformation and seepage-dissolution, and providing a model carrier and experimental method for the microscopic mechanism of seepage-dissolution-deformation in fractured media. Summary of the Invention

[0011] The purpose of this invention is to provide a microfluidic model, preparation method, and experimental method for visualizing rock seepage dissolution-deformation experiments, so as to realize the visualization observation of the coupling process of real rock deformation and seepage dissolution, and provide a model carrier and experimental method for the microscopic mechanism of seepage-dissolution-deformation in fractured media.

[0012] To achieve the above objectives, this application provides a microfluidic model for a visualization experiment of rock seepage, dissolution and deformation, comprising a transparent substrate, an intermediate functional plate and a transparent cover plate stacked and sealed from bottom to top, wherein the intermediate functional plate is provided with a device cavity and a rock stress-deformation simulation component is installed in the device cavity. The rock stress-deformation simulation component includes a rock sample, a force transmission component, and a first pressure loading element. A force transmission component is installed and fixed at one or both ends of the rock sample. A first pressure loading element is installed on the side of the force transmission component away from the rock sample. The first pressure loading element is used to apply confining pressure stress to the rock sample. The transparent cover plate is provided with a fluid inlet and an outlet. The middle functional plate is provided with an inflow channel connecting the inlet to one side of the rock sample, and an outflow channel connecting the other side of the rock sample to the outlet.

[0013] The force transmission component is divided into multiple independent loading units, each unit corresponding to a local rock sample area, and each unit is connected to an independent first pressure loading element to achieve the application of a non-uniform stress field.

[0014] The first pressure loading element is a spring, a rubber column, or a shape memory alloy. One end of the first pressure loading element abuts against the force transmission component, and the other end abuts against the device cavity.

[0015] The transparent substrate and the transparent cover plate are respectively provided with placement grooves on opposite sides, and a second pressure loading element is installed in the placement groove. The second pressure loading element is used to apply top and / or bottom lateral pressure stress to the rock sample.

[0016] The second pressure loading element is a strip-shaped piezoelectric ceramic, which is positioned away from the center of the rock sample.

[0017] The second pressure loading element is a transparent piezoelectric ceramic, which covers the upper and lower sides of the rock sample.

[0018] Each side of the transparent piezoelectric ceramic consists of multiple small pieces, each of which can independently apply lateral compressive stress to the rock sample.

[0019] The inner wall of the device cavity of the intermediate functional plate is provided with slide rail grooves on both sides of the inlet channel and the outlet channel, and slide rails are installed in the slide rail grooves.

[0020] A method for preparing a microfluidic model includes the following steps: S1. Align and machine fastening holes on the transparent substrate, intermediate functional plate and transparent cover plate, drill fluid inlet and outlet on the transparent cover plate, and machine inlet channel, outlet channel and device cavity on the intermediate functional plate; S2. The rock sample and the force transmission component are bonded together with epoxy resin adhesive, the first pressure loading element is installed, and the rock stress-deformation simulation component is assembled. S3. Embed the rock stress-deformation simulation component into the device cavity of the intermediate functional plate; S4. Stack the transparent substrate, intermediate functional board and transparent cover plate, tighten the bolts after passing them through the fastening holes, and apply sealant between the layers to complete the sealing; S5. Connect the fluid inlet to the fluid supply system, inject the reactive solution, and activate the high-speed camera system located on the upper or lower side of the microfluidic model for synchronous observation.

[0021] An experimental method based on the aforementioned microfluidic model is used to study the microscopic evolution mechanism of fractured rock masses under the coupling of seepage, dissolution, and stress fields. The experimental method includes the following steps: S1. Inject an acidic solution into the fluid inlet, controlling the flow rate to be 0.1-10 mL / min; S2. Apply confining pressure stress to the rock sample through the first pressure loading element, and continuously record the surface dissolution morphology, crack propagation path and displacement changes of the force transmission components through the transparent substrate and transparent cover plate using a high-speed camera or microscopic imaging system. S3. Based on image processing algorithms, extract the growth rate of dissolution area, the rate of change of crack opening and stress response curves, and quantitatively analyze the coupling relationship of the three fields of seepage-dissolution-deformation.

[0022] An experimental method based on the aforementioned microfluidic model is used to study the microscopic evolution mechanism of fractured rock masses under the coupling of seepage, dissolution, and stress fields. The experimental method includes the following steps: S1. Inject an acidic solution into the fluid inlet, controlling the flow rate to be 0.1-10 mL / min; S2. Apply confining pressure stress to the rock sample through the first pressure loading element, and simultaneously apply top and / or bottom lateral pressure stress to the rock sample through the second pressure loading element; use a high-speed camera or microscopic imaging system to continuously record the surface dissolution morphology, crack propagation path and displacement changes of force transmission components through a transparent substrate and a transparent cover plate. S3. Based on image processing algorithms, extract the growth rate of dissolution area, the rate of change of crack opening and stress response curves, and quantitatively analyze the coupling relationship of the three fields of seepage-dissolution-deformation.

[0023] Compared with the prior art, the above-conceptual technical solution conceived in this application has the following beneficial effects: 1. This application utilizes a sandwich structure with both upper and lower layers made of optically transparent materials, enabling high-speed cameras or microscopic imaging systems to observe in real-time, continuously, and non-destructively the evolution of dissolution morphology, fracture opening and closing behavior, and displacement response of force-transmitting components in rock samples under the action of reactive fluids. This transforms the previously invisible seepage-dissolution-deformation coupling process into a high spatiotemporal resolution image sequence, providing direct visual evidence for mechanistic research.

[0024] 2. This application constructs a bidirectional or even near-triaxial composite stress state within a microfluidic chip by setting up a first pressure loading element and a second pressure loading element to apply horizontal lateral confining pressure and vertical top / bottom pressure, respectively. This design overcomes the limitation of traditional micro-models that can only simulate unidirectional uniformly distributed stress, and can more realistically reproduce the complex mechanical environment of the underground rock mass under the combined action of overlying self-weight stress and tectonic lateral pressure. When the second pressure loading element adopts a partitioned transparent piezoelectric ceramic array, it can also realize spatially programmable non-uniform stress distribution to simulate typical geological structural scenarios such as stress difference between fault sides and gradient stress in fold limbs, greatly enhancing the geological representativeness of the experiment. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0026] Figure 1 This is a schematic diagram of the microfluidic model of the present invention.

[0027] Figure 2 This is a schematic diagram of the rock stress-deformation simulation component in this invention.

[0028] Figure 3 This is a schematic diagram of the structure of the second pressure loading element in the microfluidic model of the present invention, which is a strip-shaped piezoelectric ceramic.

[0029] Figure 4 This is a schematic diagram of the structure of the second pressure loading element in the microfluidic model of the present invention, which is a multi-piece piezoelectric ceramic.

[0030] Figure label: 1. Transparent substrate, 2. Intermediate functional plate, 3. Rock stress-deformation simulation component, 4. Transparent cover plate, 5. Fastening hole, 6. Bolt, 7. Inlet, 8. Outlet, 9. Inlet channel, 10. Device cavity, 11. Outlet channel, 12. Slide rail groove, 13. Slide rail, 14. First pressure loading element, 15. Force transmission component, 16. Rock sample, 17. Placement groove, 18. Second pressure loading element. Detailed Implementation

[0031] To more clearly illustrate the purpose, technical solution, and beneficial effects of this application, a further detailed description of this application is provided below in conjunction with illustrations and specific embodiments. It should be specifically noted that the specific embodiments described below are only for illustrating the technical content of this application and do not constitute a limitation on the scope of protection of this application.

[0032] Regarding the explanation of terminology: In this application, "and / or" is used to describe the relationship between related objects, covering three possible situations: taking "A and / or B" as an example, it can indicate the situation where only A exists, A and B exist simultaneously, or only B exists; the symbol " / " indicates the "or" relationship between related objects, such as "A / B" which refers to A or B.

[0033] Regarding the description of the embodiments: The terms "exemplary" and "for example" appearing in this application are only used to illustrate the technical solutions through specific examples. It should be particularly emphasized that any implementation method or design scheme marked as "exemplary" or "for example" should not be construed as having an advantage over other solutions. Such expressions are only used to present the technical concepts more intuitively.

[0034] Example 1: See Figure 1 , 2 The present invention provides a microfluidic model for visualization experiments of rock seepage, dissolution and deformation, comprising a transparent substrate 1, an intermediate functional plate 2 and a transparent cover plate 4 stacked and sealed from bottom to top, the intermediate functional plate 2 having a device cavity 10, and a rock stress-deformation simulation component 3 installed in the device cavity 10. The rock stress-deformation simulation component 3 includes a rock sample 16, a force transmission component 15, and a first pressure loading element 14. The force transmission component 15 is installed and fixed at one or both ends of the rock sample 16. The first pressure loading element 14 is installed on the side of the force transmission component 15 away from the rock sample 16. The first pressure loading element 14 is used to apply confining pressure stress to the rock sample 16. The transparent cover plate 4 is provided with a fluid inlet 7 and an outlet 8. The intermediate functional plate 2 is provided with an inflow channel 9 that connects the inlet 7 to one side of the rock sample 16, and an outflow channel 11 that connects the other side of the rock sample 16 to the outlet 8.

[0035] By employing a sandwich structure with optically transparent materials on both the top and bottom, combined with a transparent flow channel design, an external high-speed camera or microscopic imaging system can observe the evolution of the dissolution morphology of rock sample 16 under the action of reactive fluid in real time and without damage, such as crack widening, pore formation, and displacement or closure behavior driven by stress, thus transforming the originally invisible seepage-dissolution-deformation coupling process into visible image data.

[0036] The first pressure loading element 14 is used to apply continuous confining pressure stress to the rock sample 16. When the rock sample 16 is reduced in volume or the cracks open due to dissolution, the component can be moved and the first pressure loading element 14 dynamically adjusts the force, thereby realistically reproducing the positive and negative feedback mechanism of dissolution weakening the rock mass strength, stress redistribution, and crack closure or expansion in nature, and improving the geomechanical fidelity of the experiment.

[0037] In this embodiment, see Figure 2 Rock sample 16 has three-dimensional fractures in the middle.

[0038] In the preferred embodiment, the force transmission component 15 is divided into multiple independent loading units, each corresponding to a local rock sample area, and each unit is connected to an independent first pressure loading element 14 to achieve the application of a non-uniform stress field. The in-situ stress in natural rock masses usually has spatial non-uniformity, such as stress concentration near faults, coexistence of tectonic compression and tension zones, and differences in vertical and horizontal stress. Uniformly distributed loading cannot reflect such complex stress states, while multi-unit independent loading can set the stress magnitude and direction of different areas as needed, approximating real geological conditions.

[0039] In this embodiment, the first pressure loading element 14 is a spring, a rubber column, or a shape memory alloy. One end of the first pressure loading element 14 abuts against the force transmission member 15, and the other end abuts against the device cavity 10.

[0040] In this embodiment, the inner wall of the device cavity 10 of the inter-functional plate 2 is provided with slide rail grooves 12 on both sides of the inflow channel 9 and the outflow channel 11, and slide rails 13 are installed in the slide rail grooves 12.

[0041] During the dissolution process, rock sample 16 may experience volume shrinkage, fissure opening, or local disintegration, resulting in a slight displacement of its overall position. The slide rail 13 and the slide rail groove 12 form a guide pair, restricting the rock stress-deformation simulation component 3 to move only along the direction perpendicular to the fluid flow direction, i.e., parallel to the normal direction of the fissure surface, preventing it from lateral deflection or jamming.

[0042] Example 2: Based on Example 1, see Figure 1 The transparent substrate 1 and the transparent cover plate 4 are respectively provided with placement grooves 17 on opposite sides. A second pressure loading element 18 is installed in the placement groove 17. The second pressure loading element 18 is used to apply top and / or bottom lateral pressure stress to the rock sample 16.

[0043] The second pressure loading element 18 can apply additional compressive stress to the rock sample 16 from the top and bottom directions, i.e., parallel to the fluid flow direction or perpendicular to the plane of the rock sample 16, thereby constructing a bidirectional or even near-triaxial stress state, thus more realistically reproducing the three-dimensional mechanical environment of the underground rock mass, and supporting the study of problems such as confining pressure effect, effective stress control, and asymmetric loading.

[0044] In one of the solutions, see Figure 3 The second pressure loading element 18 is a strip-shaped piezoelectric ceramic, which is positioned away from the center of the rock sample 16. Without sacrificing visualization performance, lateral compressive stress is applied to the edge of the rock sample 16, upgrading the originally simplified uniaxial stress model into a multiaxial stress system with vertical loading capability.

[0045] In another option, see Figure 4 The second pressure loading element 18 is a transparent piezoelectric ceramic, which covers the upper and lower sides of the rock sample 16. Transparent piezoelectric ceramic is a functional material that combines optical transparency and piezoelectric effect. It allows light to pass through, enabling high-speed cameras or microscopes to directly observe the dissolution and deformation process of the rock sample 16 through the second pressure loading element 18.

[0046] Further, see Figure 4 Each side of the transparent piezoelectric ceramic comprises multiple small pieces, each capable of independently applying lateral compressive stress to the rock sample 16. The voltage of each small piezoelectric ceramic piece can be independently adjusted, thereby applying local pressure of different magnitudes at different locations on the surface of the rock sample 16. This can simulate complex mechanical environments commonly found in real geology, such as stress concentration zones, stress gradient zones, differential stress on both sides of faults, and uneven compaction of fold limbs.

[0047] Example 3: Based on Example 1, this example proposes a method for preparing a microfluidic model, including the following steps: S1. Align and machine fastening holes 5 on transparent substrate 1, intermediate functional plate 2 and transparent cover plate 4, and drill fluid inlet 7 and outlet 8 on transparent cover plate 4, and machine inlet channel 9, outlet channel 11 and device cavity 10 on intermediate functional plate 2. S2. The rock sample 16 is bonded to the force transmission component 15 with epoxy resin adhesive, the first pressure loading element 14 is installed, and the rock stress-deformation simulation component 3 is assembled. S3. Embed the rock stress-deformation simulation component 3 into the device cavity 10 of the intermediate functional plate 2; S4. Stack the transparent substrate 1, the intermediate functional board 2 and the transparent cover plate 4, tighten the bolts 6 after passing through the fastening holes 5, and apply sealant between the layers to complete the sealing. S5. Connect the fluid inlet 7 to the fluid supply system, inject the reactive solution, and activate the high-speed camera system located on the upper or lower side of the microfluidic model for synchronous observation.

[0048] The above steps enable the production and fabrication of microfluidic models.

[0049] Example 4: Based on Example 1, this example proposes an experimental method based on the microfluidic model to study the microscopic evolution mechanism of fractured rock masses under the coupling of seepage, dissolution, and stress. The experimental method includes the following steps: S1. Inject an acidic solution into fluid inlet 7, controlling the flow rate to be 0.1-10 mL / min.

[0050] By setting the acidic solution, such as dilute hydrochloric acid, and the flow rate range, seepage reaction environments of varying intensities, from slow groundwater dissolution to engineering acid fracturing, can be simulated.

[0051] S2. Apply confining pressure stress to rock sample 16 through first pressure loading element 14, and continuously record the surface erosion morphology, crack propagation path and displacement change of force transmission component 15 of rock sample 16 through transparent substrate 1 and transparent cover plate 4 using high-speed camera or microscopic imaging system.

[0052] S3. Based on image processing algorithms, extract the growth rate of dissolution area, the rate of change of crack opening and stress response curves, and quantitatively analyze the coupling relationship of the three fields of seepage-dissolution-deformation.

[0053] The rate of increase in dissolved area characterizes the chemical reaction rate, the rate of change in fissure aperture reflects the evolution of mechanical deformation and permeability, and the stress response curve reveals the effective stress adjustment process. A quantitative relationship between these three fields is established: using time series data, models such as the relationship between dissolved rate and stress level, the evolution of fissure aperture and cumulative dissolved amount, and the feedback model between permeability and effective stress can be constructed.

[0054] This experimental method bridges the key gap between microscopic experimental phenomena and macroscopic engineering laws, providing an experimental research paradigm for major needs such as deep karst development prediction, CO2 geological storage safety assessment, shale gas acidification production enhancement optimization, and karst collapse disaster early warning.

[0055] Example 5: Based on Example 2, this example provides an experimental method based on the microfluidic model to study the microscopic evolution mechanism of fractured rock masses under the coupling of seepage, dissolution, and stress fields. The experimental method includes the following steps: S1. Inject acidic solution into fluid inlet 7, controlling the flow rate to be 0.1-10 mL / min; S2. Apply confining pressure stress to rock sample 16 through first pressure loading element 14, and apply top and / or bottom lateral pressure stress to rock sample 16 through second pressure loading element 18; use a high-speed camera or microscopic imaging system to continuously record the surface dissolution morphology, crack propagation path and displacement change of force transmission component 15 of rock sample 16 through transparent substrate 1 and transparent cover plate 4. S3. Based on image processing algorithms, extract the growth rate of dissolution area, the rate of change of crack opening and stress response curves, and quantitatively analyze the coupling relationship of the three fields of seepage-dissolution-deformation.

[0056] This embodiment adds a second pressure loading element 18 to apply top and / or bottom lateral pressure stress to the rock sample 16, which works in conjunction with the first pressure loading element 14 to construct a multi-directional stress environment that more closely resembles the real strata. This enables the study of the microscopic evolution mechanism of fractured rock masses under the multi-field coupling of seepage-dissolution-stress.

[0057] The first pressure loading element 14 provides horizontal lateral confining pressure to simulate tectonic compression or lateral in-situ stress. The second pressure loading element 18 provides vertical top / bottom pressure, and the top and bottom loading forces can be independently controlled to simulate vertical stress gradients caused by tilted strata, fault drag, or injection-production disturbances. The combination of the two can simulate biaxial or even near-triaxial stress states, approximating the actual stress environment of underground rock masses.

[0058] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0059] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A microfluidic model for visualizing rock seepage, dissolution, and deformation experiments, characterized in that: It includes a transparent substrate (1), an intermediate functional plate (2) and a transparent cover plate (4) stacked and sealed from bottom to top. The intermediate functional plate (2) has a device cavity (10) and a rock stress-deformation simulation component (3) is installed in the device cavity (10). The rock stress-deformation simulation component (3) includes a rock sample (16), a force transmission component (15), and a first pressure loading element (14). The force transmission component (15) is fixed at one or both ends of the rock sample (16). The first pressure loading element (14) is installed on the side of the force transmission component (15) away from the rock sample (16). The first pressure loading element (14) is used to apply confining pressure stress to the rock sample (16). The transparent cover plate (4) is provided with a fluid inlet (7) and an outlet (8). The intermediate functional plate (2) is provided with an inflow channel (9) connecting the inlet (7) and one side of the rock sample (16), and an outflow channel (11) connecting the other side of the rock sample (16) and the outlet (8).

2. The microfluidic model for visualizing rock seepage, dissolution, and deformation experiments according to claim 1, characterized in that, The force transmission component (15) is divided into multiple independent loading units, each unit corresponding to a local rock sample area, and connected to an independent first pressure loading element (14) to achieve the application of a non-uniform stress field.

3. The microfluidic model for visualizing rock seepage dissolution-deformation experiments according to claim 1 or 2, characterized in that: The first pressure loading element (14) is a spring, a rubber column, or a shape memory alloy. One end of the first pressure loading element (14) abuts against the force transmission member (15), and the other end abuts against the device cavity (10).

4. The microfluidic model for visualizing rock seepage, dissolution, and deformation experiments according to claim 1, characterized in that, The transparent substrate (1) and the transparent cover plate (4) are respectively provided with placement grooves (17) on opposite sides. A second pressure loading element (18) is installed in the placement groove (17). The second pressure loading element (18) is used to apply top and / or bottom lateral pressure stress to the rock sample (16).

5. The microfluidic model for visualizing rock seepage, dissolution, and deformation according to claim 4, characterized in that, The second pressure loading element (18) is a strip-shaped piezoelectric ceramic, which is placed in a position away from the center of the rock sample (16).

6. The microfluidic model for visualizing rock seepage, dissolution, and deformation experiments according to claim 4, characterized in that, The second pressure loading element (18) is a transparent piezoelectric ceramic, which covers the upper and lower sides of the rock sample (16).

7. The microfluidic model for visualizing rock seepage, dissolution, and deformation experiments according to claim 6, characterized in that, Each side of the transparent piezoelectric ceramic comprises multiple small pieces, each of which can independently apply lateral compressive stress to the rock sample (16).

8. The microfluidic model for visualizing rock seepage, dissolution, and deformation according to claim 1, characterized in that, The inner wall of the device cavity (10) of the intermediate functional plate (2) is provided with slide rail grooves (12) on both sides of the inflow channel (9) and the outflow channel (11), and slide rails (13) are installed in the slide rail grooves (12).

9. A method for preparing a microfluidic model as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Align and machine fastening holes (5) on the transparent substrate (1), the intermediate functional plate (2) and the transparent cover plate (4), and drill fluid inlet (7) and outlet (8) on the transparent cover plate (4), and machine inlet channel (9), outlet channel (11) and device cavity (10) on the intermediate functional plate (2). S2. The rock sample (16) and the force transmission component (15) are bonded together with epoxy resin adhesive, the first pressure loading element (14) is installed, and the rock stress-deformation simulation component (3) is assembled. S3. Embed the rock stress-deformation simulation component (3) into the device cavity (10) of the intermediate functional plate (2); S4. Stack the transparent substrate (1), the intermediate functional board (2) and the transparent cover plate (4), tighten the bolts after passing through the fastening holes (5), and apply sealant between the layers to complete the sealing; S5. Connect the fluid inlet (7) to the fluid supply system, inject the reactive solution, and start the high-speed camera system located on the upper or lower side of the microfluidic model for synchronous observation.

10. An experimental method based on the microfluidic model of claim 1, characterized in that, To study the microscopic evolution mechanism of fractured rock masses under the coupling of seepage, dissolution, and stress, the experimental method includes the following steps: S1. Inject acidic solution into fluid inlet (7) and control the flow rate to 0.1–10 mL / min; S2. Apply confining pressure stress to the rock sample (16) through the first pressure loading element (14), and continuously record the surface dissolution morphology, crack propagation path and displacement change of the force transmission component (15) of the rock sample (16) through the transparent substrate (1) and transparent cover plate (4) using a high-speed camera or microscopic imaging system. S3. Based on image processing algorithms, extract the growth rate of dissolution area, the rate of change of crack opening and stress response curves, and quantitatively analyze the coupling relationship of the three fields of seepage-dissolution-deformation.

11. An experimental method based on the microfluidic model according to any one of claims 4 to 7, characterized in that, To study the microscopic evolution mechanism of fractured rock masses under the coupling of seepage, dissolution, and stress, the experimental method includes the following steps: S1. Inject acidic solution into fluid inlet (7) and control the flow rate to 0.1–10 mL / min; S2. Apply confining pressure stress to the rock sample (16) through the first pressure loading element (14), and apply top and / or bottom lateral pressure stress to the rock sample (16) through the second pressure loading element (18); use a high-speed camera or microscopic imaging system to continuously record the surface dissolution morphology, crack propagation path and displacement changes of the force transmission component (15) of the rock sample (16) through the transparent substrate (1) and the transparent cover plate (4); S3. Based on image processing algorithms, extract the growth rate of dissolution area, the rate of change of crack opening and stress response curves, and quantitatively analyze the coupling relationship of the three fields of seepage-dissolution-deformation.

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