A fracture porous matrix coupling system seepage electromagnetic cooperative testing device and method

Abstract

The application discloses a kind of fracture porous matrix coupling system percolation electromagnetic collaborative testing device and method, comprising: sample module, by the first porous matrix sample and the second porous matrix sample of relative arrangement, form fracture passage between two porous matrix samples;Fracture formation and end control fracture module, for keeping the preset opening of the fracture passage and constituting the boundary basis of end flow acquisition;Integral sealing module, for the integral casting sealing of the periphery of the sample module;Fluid injection and boundary control module, for providing one-way water drive fluid to the fracture passage and the two matrix samples on both sides and switching different flow boundary mode;Outlet shunt acquisition module, for independently exporting and real-time acquisition the outflow of the fracture passage and the porous matrix sample on both sides;Pressure monitoring module, for obtaining the pressure information of injection end and outflow end;Electromagnetic detection module, for collecting electromagnetic response information of fracture region and adjacent matrix sample region.

Description

Technical Field

[0001] This application relates to the field of soil and rock seepage testing and non-destructive testing technology for underground engineering, and in particular to an electromagnetic synergistic testing device and method for seepage in a coupled system of fractured porous matrix. Background Technology

[0002] Cracks and interface defects are widely present in underground engineering and geotechnical media, such as the wellbore cement sheath-stratum interface, tunnel lining-surrounding rock interface, grout-bedrock interface, and layered media contact interface. Once formed, these defects often become dominant channels for fluid transport, thus affecting the sealing performance, service stability, and long-term safety of underground structures. Especially in scenarios such as groundwater seepage, gas and energy storage, wellbore sealing, and underground structure seepage prevention, cracks not only determine the formation and expansion of fluid channels but may also induce problems such as local leakage, pressure anomalies, and structural deterioration. Therefore, research on the flow behavior of cracks and crack-porous matrix systems has significant engineering implications.

[0003] Existing research on fracture seepage typically focuses on the influence of fracture conductivity, pressure-flow differential, or fracture surface roughness on flow characteristics. However, in actual underground media, fractures do not exist in isolation but often form coupled flow systems with the porous matrix on both sides. While fluids migrate along the main channel within the fracture, they also exchange flow rates, transmit pressures, and migrate localized water aquifers with the adjacent matrix, resulting in fracture flow exhibiting significant dynamic, non-uniform, and coupled characteristics. Traditional experimental methods often struggle to simultaneously distinguish between the main fracture channel flow and the fracture-matrix exchange flow, thus making it difficult to accurately reveal the synergistic mechanisms between fracture conductivity, diversion, and exchange.

[0004] On the other hand, the state of a fracture is not merely manifested in changes in geometric opening or spatial location; the internal fluid state, water content distribution, and seepage process also alter the physical properties of the fracture medium, particularly causing changes in dielectric properties and electromagnetic response. High-frequency electromagnetic detection technology is highly sensitive to differences in the electrical properties of the medium, changes in water content, and interfacial discontinuities, thus possessing potential advantages in fracture identification, water anomaly detection, and subsurface interface condition assessment. Mechanistically, the fracture seepage process leads to the continuous evolution of the water content in the fracture and adjacent matrix areas, which directly affects the propagation, reflection, and scattering characteristics of electromagnetic waves. Therefore, fracture seepage behavior and electromagnetic detection response have a clear physical coupling basis and are not two independent technical directions.

[0005] However, in existing technologies, fracture seepage testing devices and electromagnetic detection characterization methods are mostly conducted separately: the former focuses on measuring flow rate, pressure, and conductivity, while the latter focuses on interface identification or analysis of abnormal media responses. There is a lack of experimental devices and testing methods that can simultaneously achieve fracture main channel flow testing, fracture-matrix flow exchange monitoring, and interface electromagnetic response characterization under controllable unidirectional driving conditions. In particular, for fracture systems with rough interfaces, asymmetric permeability matrices, and dynamic water content changes, there is a lack of effective technical means to simultaneously establish the correlation between "fracture structure-seepage behavior-electromagnetic response." Therefore, it is necessary to propose an experimental device and testing method for fracture-porous matrix coupled systems to achieve synergistic research on fracture flow exchange characteristics and their electromagnetic characterization laws. Summary of the Invention

[0006] To address the aforementioned issues, this application provides a device and method for synergistic electromagnetic co-testing of seepage in a coupled fractured porous matrix system, enabling synergistic research on the flow exchange characteristics of fractures and their electromagnetic characterization laws. The technical solution is as follows: This application provides a seepage electromagnetic co-testing device for a fractured porous matrix coupled system, comprising: a sample module, consisting of a first porous matrix sample and a second porous matrix sample arranged opposite to each other, with a fracture channel extending along the main flow direction between the two porous matrix samples; a fracture formation and end control module, disposed at the upstream and downstream ends of the sample module, for maintaining a preset opening of the fracture channel and forming a boundary foundation for end flow acquisition; an integral sealing module, for integrally casting and sealing the periphery of the sample module to form an external sealing structure capable of withstanding injection pressure; and a fluid injection and boundary control module, for injecting fluid into the fracture channel and the... The first and second porous matrix samples on both sides of the fracture channel are provided with unidirectional water-driven fluid and switch between different flow boundary modes. An outlet diversion acquisition module, located downstream of the sample module, consists of multiple independent external receiver structures and is used to independently export and collect in real time the outflow rate of the fracture channel and the porous matrix samples on both sides of the fracture channel. A pressure monitoring module, located upstream and downstream of the sample module, is used to acquire pressure information at the injection and outflow ends. An electromagnetic detection module, arranged on the external test surface of the overall sealing module, is used to collect electromagnetic response information of the fracture region and adjacent matrix sample regions. According to the above embodiment, by integrating the sample module, fracture control module, overall sealing module, fluid injection and boundary control module, outlet diversion acquisition module, pressure monitoring module, and electromagnetic detection module, an integrated seepage-electromagnetic collaborative testing platform for fracture-porous matrix coupled systems is constructed. It can simultaneously conduct flow tests in the main channel of cracks, monitor flow exchange between cracks and the matrix, and collect electromagnetic responses at the interface. This solves the problem of the separation between seepage testing and electromagnetic detection in existing technologies, which makes it difficult to establish a corresponding relationship. It provides a unified experimental basis for studying the correlation between crack structural state, flow behavior and electromagnetic characterization.

[0007] For example, in one embodiment of the electromagnetic co-testing device for a fractured porous matrix coupled system, the fracture formation and end-crack control module includes a T-shaped spacer disposed in the inlet and outlet region of the fracture channel. The T-shaped spacer is sandwiched between the first porous matrix sample and the second porous matrix sample to maintain a fracture channel with a constant opening. According to the above embodiment, by setting a T-shaped spacer sandwiched between the two matrices in the fracture inlet and outlet region, the fracture opening can be stably controlled and the clarity of the fracture boundary can be ensured. This avoids changes in the fracture opening caused by fluid pressure fluctuations or sample deformation, and improves the repeatability and reliability of the test results.

[0008] For example, in one embodiment of the electromagnetic co-processing testing device for a fractured porous matrix coupled system, the outlet diversion acquisition module includes three independent external receiving collection structures, corresponding to the outlet of the first porous matrix sample, the outlet of the fracture channel, and the outlet of the second porous matrix sample, respectively. According to the above embodiment, by setting three independent external receiving collection structures corresponding to the outlets of the first porous matrix sample, the fracture channel, and the second porous matrix sample, the physical separation and independent acquisition of the outflow from the fracture channel and the outflow from the matrix on both sides are achieved. This enables the quantitative differentiation between the fracture-dominated flow and the fracture-matrix exchange flow, providing a direct measurement method for analyzing the diversion ratio and exchange intensity.

[0009] For example, in one embodiment of the electromagnetic co-testing device for the fractured porous matrix coupled system, the outlet diversion acquisition module further includes: a flow collection box, connected to the end of the sample module, and corresponding to the end regions of the first porous matrix sample, the fracture channel, and the second porous matrix sample, respectively; a silicone sealing gasket, disposed between the flow collection box and the end face of the sample module; wherein the silicone sealing gasket and the bottom of the flow collection box are provided with a grooved air outlet and a flow guide, for realizing independent flow guidance and collection of the three fluids; the three outlet branches are respectively connected to a beaker and an electronic balance to monitor the three outflow rates in real time. According to the above embodiment, through the specific cooperation of the flow collection box, silicone sealing gasket, grooved flow guide structure, and electronic balance, under the condition of ensuring high-pressure sealing at the end, low-interference, high-precision independent flow guidance and real-time weighing of the three fluids are achieved, avoiding the problem of destroying the integrity due to cutting the end of the sample in the traditional method, while improving the sensitivity and accuracy of flow acquisition.

[0010] For example, in one embodiment of the seepage electromagnetic synergistic testing device for a fractured porous matrix coupling system, the integral sealing module is formed by integrally casting and sealing the periphery of the sample module with resin material to form an integral resin sealing structure; before casting, a water-proof acrylic plate is pasted on the inner side of the fracture channel to prevent resin from penetrating into the fracture; the integral resin sealing structure covers the periphery of the first porous matrix sample and the second porous matrix sample, the outer side of the flow collection box at its ends, and the periphery of the T-shaped spacer strip, and the inner side of the fracture channel, the upstream and downstream surfaces of the first porous matrix sample and the second porous matrix sample, and the inlet and outlet areas of the fracture channel are exposed outside the integral resin sealing structure. According to the above embodiment, by using integral resin casting and sealing, and pasting a water-proof acrylic plate on the inner side of the fracture before casting, an integral external sealing structure capable of withstanding high injection pressure is formed, while ensuring that the cavity inside the fracture is not penetrated by resin, thereby improving the pressure resistance of the device and ensuring that the flow exchange between the main fracture channel and the two side matrices is not blocked.

[0011] For example, in one embodiment of the electromagnetic co-current testing device for a fractured porous matrix coupled system, the fluid injection and boundary control module includes a storage unit, a drive pump, an inlet pipe, and independent valve assemblies located at the upstream and downstream ends. The independent valve assemblies control the opening and closing states of the first porous matrix sample branch, the fracture channel branch, and the second porous matrix sample branch, respectively, to achieve switching between a single-fracture flow mode and a fracture-matrix coupled flow mode. According to the above embodiment, by setting valve assemblies that independently control each branch at the upstream and downstream ends, the single-fracture flow mode and the fracture-matrix coupled flow mode can be flexibly switched. Intrinsic fracture flow testing and coupling exchange testing can be performed sequentially on the same sample, eliminating the influence of sample differences on the comparison results and improving experimental efficiency and data comparability.

[0012] For example, in one embodiment of the electromagnetic co-testing device for seepage in a fractured porous matrix coupled system, the electromagnetic detection module is a transceiver integrated step-frequency continuous wave radar probe. When arranged on the external test surface of the device, the electromagnetic wave propagation path sequentially passes through the resin integral sealing structure, the first porous matrix sample, the fracture channel region, the second porous matrix sample, and the resin integral sealing structure outside the second porous matrix sample. According to the above embodiment, by using a transceiver integrated step-frequency continuous wave radar probe and defining the electromagnetic wave propagation path to sequentially pass through the outer sealing layer, the first matrix, the fracture, the second matrix, and the corresponding outer sealing layer, high-resolution non-destructive detection of the water content and interface structure of the fracture region and adjacent matrix can be performed. Moreover, the detection path spatially overlaps with the seepage path, so that the electromagnetic response and seepage behavior have a direct physical correspondence, which facilitates the establishment of a correlation model between the two.

[0013] The second aspect of this application provides a method for electromagnetic co-testing of seepage in a fractured porous matrix coupled system, comprising the following steps: S1: preparing a first porous matrix sample and a second porous matrix sample, forming a preset fracture channel region between the two, assembling a fracture formation and end fracture control module and an outlet flow acquisition module, and then using an integral sealing module to integrally seal the periphery of the sample to form an integrated sample assembly; S2: connecting a fluid injection and boundary control module, a pressure monitoring module, and an electromagnetic detection module to the integrated sample assembly respectively; S3: adjusting the boundary control module according to the test objective, setting it to... S4: Start the drive pump to inject aqueous fluid into the sample inlet at a preset flow rate, forming a unidirectional water-driven process; S5: During fluid injection, collect upstream pressure, downstream pressure, and multi-channel outlet flow data in real time; S6: During seepage, use the electromagnetic detection module to detect the target area of ​​the sample and obtain electromagnetic response information of the fracture area and adjacent matrix area; S7: Perform joint analysis on the collected flow rate, pressure, and electromagnetic response data to establish the correspondence between fracture channel flow, fracture matrix exchange behavior, and interface electromagnetic characterization. According to the above embodiment, by sequentially executing the steps of sample preparation, module connection, boundary mode setting, unidirectional water injection drive, hydraulic parameter acquisition, electromagnetic response acquisition, and joint analysis, the effect is that the functions of each module of the device are transformed into a standardized and repeatable test process, realizing the whole chain operation from sample preparation to data joint analysis, ensuring the feasibility of seepage-electromagnetic synergistic testing and the reproducibility of results.

[0014] For example, in the electromagnetic co-testing method for seepage in a fractured porous matrix coupled system provided in one embodiment, in step S3, the single-fracture flow mode is: only the fracture channel branch is opened upstream, only the outlet of the fracture channel branch is opened downstream, and both matrix sample branches are closed; the fractured matrix coupled flow mode is: the fracture channel branch is opened upstream, and the outlets of the first porous matrix sample branch, the fracture channel branch, and the second porous matrix sample branch are opened simultaneously downstream. According to the above embodiment, by clearly defining that only the fracture branch is opened in the single-fracture mode and that the fracture and both matrix outlet branches are opened simultaneously in the coupled mode, the effect is that it provides specific operating methods for two extreme boundary conditions, enabling operators to clearly perform mode switching, and making the flow rate difference obtained in the two modes directly reflect the degree of fracture-matrix exchange, avoiding experimental errors caused by unclear valve settings.

[0015] For example, in the electromagnetic co-testing method for seepage in a fractured porous matrix coupled system provided in one embodiment, in step S6, electromagnetic detection employs at least one of the following methods: real-time monitoring: continuously or at set time intervals during water drive to track the dynamic evolution of the water-gas interface inside the fracture; steady-state monitoring: after fluid breakthrough or reaching a preset stable state, time-division testing is performed on the sample to analyze the electromagnetic response characteristics corresponding to the fluid distribution state within the fractured dual-matrix structure. According to the above embodiment, by limiting the real-time monitoring method to track the dynamic evolution of the water-gas interface and the steady-state monitoring method to analyze the electromagnetic characteristics corresponding to the fluid distribution state, the effect is that: the detection strategy with flexible temporal and spatial resolution can be selected according to the research objective; it can capture the transient process at the seepage front and obtain a fine electromagnetic image under stable conditions, thereby meeting the research needs of seepage-electromagnetic coupling laws at different scales.

[0016] The electromagnetic co-testing device and method for seepage in a cracked porous matrix coupled system provided in some embodiments of this application have the following significant advantages: (1) A seepage-electromagnetic synergistic testing platform for fracture-porous matrix coupled system was constructed, which can realize the main channel flow test of fracture, flow exchange monitoring of fracture-matrix and electromagnetic response acquisition in the same device. It overcomes the problem that seepage test and electromagnetic detection are separated in the prior art and it is difficult to establish a corresponding relationship, thus providing a unified experimental basis for the study of the correlation between fracture structural state, flow behavior and electromagnetic characterization.

[0017] (2) By setting up independent valve components for upstream and downstream and three independent flow acquisition structures, the fluid boundary mode can be switched controllably. It can realize both single crack flow test and crack-matrix coupled flow test. It can also independently acquire the outflow of the first porous matrix sample, the outflow of the crack channel and the outflow of the second porous matrix sample, thereby realizing the separation measurement of crack channel flow and crack-matrix exchange flow, and improving the ability to identify the coupled seepage mechanism.

[0018] (3) The end control and overall sealing structure combining T-shaped custom spacer strip, flow collection box, silicone sealing gasket and resin integral casting external sealing can not only stably control the crack opening and ensure the crack boundary is clear, but also maintain good sealing performance and structural stability under high injection pressure conditions, thereby improving the reliability and repeatability of test results.

[0019] (4) The flow acquisition method adopts three external independent collection tanks and is combined with electronic balance for real-time monitoring. It can realize independent flow acquisition from the two sides of the matrix and the main channel of the crack without cutting and separating the sample end. This structure is conducive to accurately obtaining the three-way flow information while maintaining the integrity and sealing of the sample, and is suitable for studying the flow difference under symmetrical or asymmetrical matrix conditions.

[0020] (5) By setting up upstream and downstream pressure monitoring modules and combining the real-time acquisition results of three flow channels, key hydraulic parameters such as pressure drop, pressure gradient, flow split ratio and exchange intensity can be obtained simultaneously, thereby achieving a comprehensive characterization of the flow conduction capacity of the fracture channel, the overall flow resistance and the fracture-matrix exchange behavior. Compared with traditional methods that only measure the total flow or only measure a single pressure difference, this application is more complete in terms of parameter acquisition dimensions.

[0021] (6) Integrating the high-frequency electromagnetic detection module directly into the fracture seepage testing platform enables real-time or steady-state detection of the fracture region and adjacent matrix region during unidirectional water drive. This allows for both tracking the dynamic changes of the water-air interface during seepage and analyzing the fluid distribution in the fracture-double matrix structure after fluid breakthrough. This technical approach expands electromagnetic detection beyond static geometric identification, enabling it to further serve the non-destructive characterization of the dynamic process of fracture seepage.

[0022] (7) This application is applicable to the testing of crack-matrix systems with different interface roughness, different matrix permeability combinations and different boundary modes. It can study the influence of rough interface, permeability asymmetric structure and flow mode changes on crack flow, diversion exchange and electromagnetic response. Therefore, it has strong scalability and applicability, and can provide technical support for the identification of interface defects in underground engineering, the evaluation of seepage prevention and sealing and related seepage-detection collaborative research.

[0023] In summary, this application not only solves the problems of difficulty in distinguishing between fracture flow and matrix flow and difficulty in simultaneously acquiring flow and detection information in traditional fracture seepage tests, but also provides an experimental equipment and testing method with a well-defined structure, controllable boundaries, and separable data acquisition for the synergistic characterization of fracture interface state, fluid transport process, and electromagnetic response characteristics. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1A schematic diagram of a two-phase flow permeation device for a fractured matrix with dual media. Figure 2 This is a schematic diagram of the sample module structure; Figure 3 This is a schematic diagram of the flow collection box structure; Figure 4 This is a diagram of a co-current electromagnetic testing system for seepage in a fractured porous matrix coupled system. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0028] I. Overall Structure of the Device like Figure 1-4 As shown, this application provides an experimental apparatus for seepage testing and electromagnetic synergistic characterization of a fracture-porous matrix coupled system. The apparatus includes: a sample module 10, a fracture formation and end-crack control module 20, an overall sealing module 30, a fluid injection and boundary control module 40, an outlet diversion acquisition module 50, a pressure monitoring module 60, and an electromagnetic detection module 70.

[0029] II. Specific Implementation Methods of Each Module 2.1 Sample Module The sample module 10 consists of a first porous matrix sample 11 and a second porous matrix sample 12 arranged opposite to each other, forming a crack channel 13 extending along the mainstream direction between them. The dimensions of a single sample are preferably 8cm × 12cm × 20cm, where 20cm is the length in the mainstream direction, 12cm is the width dimension in the crack surface direction, and 8cm is the thickness dimension in the sample direction. The interface between the two samples can be prepared with different roughness levels to simulate the crack-matrix coupling structure under different interface states. The porous matrix is ​​preferably an artificial porous media material prepared using shale ceramsite as aggregate, and sample surfaces with different interface roughness levels are obtained through a pre-fabricated rough substrate molding method.

[0030] 2.2 Crack Formation and End-of-Crack Control Module The crack formation and end-crack control module 20 is located at the upstream and downstream ends of the sample, and preferably uses customized T-shaped spacers to control the crack opening. The T-shaped spacers are positioned in the crack inlet and outlet regions to maintain a preset distance between the two porous substrates, thereby forming a crack channel with a constant opening. In this embodiment, the crack opening is preferably set to 5 mm. The T-shaped spacers not only control the crack geometry but also, in conjunction with the flow acquisition structure, constitute the basic structure for crack control and flow diversion at the sample end, ensuring that the crack opening remains stable under high-pressure injection conditions and maintaining the clear boundaries of each flow branch.

[0031] 2.3 Overall Sealing Module The integral sealing module 30 uses resin material to integrally seal the periphery of the sample, forming an external sealing structure capable of withstanding high injection pressure. To prevent resin material from penetrating into the crack during casting, a waterproof acrylic plate is pre-attached to the corresponding interface of the crack to isolate and protect the inner area of ​​the crack. After casting, the interior of the crack remains a cavity channel, ensuring that the flow exchange between the crack channel and the substrate on both sides is not blocked by the external sealing resin. The integral resin sealing structure does not cover the inner side of the crack, nor does it block the upstream and downstream substrate surfaces or the crack inlet and outlet areas, ensuring that a controlled seepage boundary is established. Through this integral resin external sealing, the sealing performance and pressure resistance of the device can be significantly improved, preferably withstanding an injection pressure of 1 MPa.

[0032] 2.4 Fluid Injection and Boundary Control Module The fluid injection and boundary control module 40 includes a storage unit 41, a drive pump 42, an inlet connection pipe 43, and independent valve assemblies 44 located at the upstream and downstream ends. The drive pump 42 is connected to the sample inlet end and provides unidirectional water-driven fluid to the fracture-matrix system. A fracture flow inlet a is located upstream of the fracture channel, and a fracture flow outlet b is located downstream of the fracture channel. Matrix flow inlets c are located upstream of the two matrix samples, and matrix flow outlets d are located downstream of the two matrix samples. The inlet connection pipe 43 is connected to a and c respectively. The upstream and downstream valve assemblies can control the opening and closing states of the fracture branch and the two matrix branches on both sides, thereby achieving switching between different test boundary modes. By independently controlling the valves of each branch at the inlet and outlet ends, the fluid can selectively enter only the fracture channel, or simultaneously enter both the fracture and matrix regions. Similarly, the downstream end can also independently open or close each branch. Therefore, the device can be used for both single-fracture flow testing and fracture-matrix coupled flow testing.

[0033] 2.5 Outlet Diversion Data Acquisition Module The outlet diversion and acquisition module 50 is located at the downstream end of the sample and consists of three independent external receiving and collecting structures connected to the end of the sample. The three outlets are not formed by cutting the sample end, but rather by connecting external flow collection grooves to correspond to the outlets of the first porous matrix sample, the crack channel, and the second porous matrix sample, respectively, to achieve independent outflow and collection of the three fluid streams. The outlet end adopts a flow collection box 51 structure, with a silicone sealing gasket 52 placed between the flow collection box 51 and the matrix surface to enhance the end sealing performance. Grooved air outlets and guide ports are provided on the sealing gasket and the bottom surface of the flow collection box to ensure airtightness while independently guiding and collecting the fluids from the first porous matrix sample, the crack channel, and the second porous matrix sample. Each outlet branch is connected to a beaker 53 and an electronic balance 54 to monitor the three outflow rates in real time, thereby obtaining the outflow rate Q1 of the first porous matrix sample, the flow rate Q2 of the crack channel, and the outflow rate Q3 of the second porous matrix sample, respectively.

[0034] 2.6 Pressure Monitoring Module The pressure monitoring module 60 is positioned upstream and downstream of the sample to acquire pressure information at the injection and effluent ends, respectively. By comparing the upstream and downstream pressures, the pressure drop response of the fracture-matrix coupled system under different boundary modes and flow rates can be obtained, and the pressure gradient, apparent flow resistance, and their evolution characteristics can be further calculated. The pressure monitoring module works in conjunction with the flow rate diversion acquisition module to achieve a comprehensive characterization of the flow conductivity of the fracture main channel, the fracture-matrix exchange strength, and the overall flow response of the coupled system.

[0035] 2.7 Electromagnetic Detection Module The electromagnetic detection module 70 preferably employs the Proceq GP8800 radar, a transceiver integrated step-frequency continuous-wave radar probe. During testing, the electromagnetic probe is positioned on the external test surface of the device. Electromagnetic waves sequentially pass through the resin outer sealing layer, the first porous matrix sample, the crack channel region, the second porous matrix sample, and the corresponding outer sealing layer, thereby acquiring electromagnetic response information of the crack region and adjacent matrix region. The electromagnetic detection module can perform real-time monitoring during seepage to track the dynamic evolution of the water-air interface; it can also select a steady-state point after fluid breakthrough for time-division testing to analyze the fluid distribution state in the crack-double matrix structure and the corresponding differences in electromagnetic response.

[0036] III. Test Method Examples Example 1: Construction of the experimental setup This embodiment provides an experimental apparatus for co-testing seepage and electromagnetic interference in a fracture-porous matrix coupled system. The specific construction steps are as follows: The first and second porous matrix samples were prepared as block-shaped porous media specimens, arranged opposite each other along the thickness direction, with a crack region formed between their interfaces. Each specimen measures 8cm × 12cm × 20cm. The interfaces between the two specimens can be prepared with different roughness levels.

[0037] To prevent resin material from penetrating the cracks during subsequent overall casting, waterproof acrylic sheets are pre-attached to the opposing surfaces of the two specimens where cracks are to be formed, providing temporary isolation and protection for the inside of the cracks. Subsequently, customized T-shaped spacers are placed at the upstream and downstream ends of the specimens to control the spacing between the two specimens and form a crack channel with a preset opening. In this embodiment, the crack opening is preferably set to 5 mm. The T-shaped spacers are placed in the inlet and outlet areas of the crack.

[0038] Flow collection boxes are installed at the upstream and downstream ends of the sample, respectively communicating with the end regions of the first porous matrix sample, the crack channel, and the second porous matrix sample. A silicone sealing gasket is placed between the flow collection box and the sample end face, fitting snugly to the bottom of the flow collection box and featuring a recessed air outlet and a flow guide to ensure end sealing while enabling independent flow guidance and collection of the three fluid streams. The T-shaped spacer and the flow collection boxes on both sides together constitute an integrated crack control and flow diversion assembly at the sample end.

[0039] After assembling the sample, spacer, flow collection box, and sealing gasket, the sample is integrally sealed with resin material to form a monolithic external seal structure. This integral resin seal covers the porous substrate, the outer side of the end flow collection box, and the outer side of the T-shaped spacer, but does not block the internal channels of the cracks or cover the actual upstream and downstream inflow / outflow areas. This integrally cast structure can withstand injection pressures not exceeding 1 MPa.

[0040] Example 2: Fluid Injection and Boundary Control Structure The fluid injection assembly includes a liquid storage container, a drive pump, and an inlet pipe connected to the sample inlet end. The boundary control assembly includes independent valve assemblies respectively arranged at the upstream and downstream ends of the sample. The valve assemblies correspond to the first porous matrix sample branch, the crack channel branch, and the second porous matrix sample branch, respectively, to achieve independent opening and closing control of each branch on the inlet and outlet sides.

[0041] By controlling the upstream valve assembly, it is possible to select whether the injected fluid enters only the fracture channel or simultaneously enters the fracture and the matrix regions on both sides; by controlling the downstream valve assembly, it is possible to select whether only the fracture channel outlet is opened or all three outlet branches are opened simultaneously. Therefore, the device can achieve at least the following two testing modes: Single-fracture flow test mode: Only the fracture branch is opened upstream, and only the fracture outlet branch is opened downstream; all other matrix branches are closed. The injected fluid mainly flows along the main fracture channel to determine the fracture's intrinsic conductivity, pressure drop response, and flow characteristics.

[0042] Crack-matrix coupled flow test mode: The crack branch is opened upstream, and the first porous matrix sample outlet branch, the crack outlet branch, and the second porous matrix sample outlet branch are opened simultaneously downstream. As the fluid advances within the crack, it exchanges flow with the porous matrix on both sides, forming three independent outflows downstream. This is used to determine the coupling characteristics between the main crack channel flow and the crack-matrix exchange flow.

[0043] Preferably, before performing coupled flow testing, a single-fracture flow test is first performed on the same sample to obtain the baseline flow response of the main channel of the fracture; then, the coupled flow mode is switched to carry out fracture-matrix exchange testing to avoid the accuracy of the single-fracture flow baseline test being affected by residual water content in the matrix after the sample has undergone coupled seepage.

[0044] Example 3: Outlet diversion data collection and pressure monitoring Three independent outlet sampling branches are set up downstream, corresponding to the outflow of the first porous matrix sample, the outflow of the main channel of the crack, and the outflow of the second porous matrix sample, respectively. Each outlet branch is connected to a beaker and an electronic balance to acquire the mass change data of the corresponding branch in real time, and convert it into the flow rates of the three branches, which are denoted as Q1, Q2 and Q3, respectively.

[0045] Pressure sensors are installed upstream and downstream of the sample to acquire pressure information at the injection and effluent ends. By collecting upstream and downstream pressure data, the pressure drop of the sample under different test modes and injection conditions can be calculated, and the pressure gradient can also be calculated by combining the effective distance between the two measuring points.

[0046] Example 4: Electromagnetic Detection Structure and Acquisition Method The electromagnetic detection component preferably uses the Proceq GP8800 structural radar. During testing, the radar probe is placed on the external test surface of the sample and detection is performed along a predetermined test line or at a target location. The electromagnetic wave propagation path sequentially passes through the resin outer sealing layer, the first porous matrix sample, the crack region, the second porous matrix sample and its outer sealing layer, thereby obtaining the electromagnetic response information of the crack region and the adjacent matrix region.

[0047] Preferably, electromagnetic detection can employ two acquisition methods: Real-time monitoring method: Electromagnetic response is continuously or intermittently collected during unidirectional water drive to track the dynamic changes of the water-air interface within the crack area.

[0048] Steady-state point monitoring method: After the fluid breaks through and reaches a preset steady state, phased data collection is carried out to characterize the fluid distribution state and its corresponding electromagnetic characteristics in the crack-double matrix structure.

[0049] Example 5: Test Procedure

[0050] Based on the above-described apparatus, this embodiment provides a method for co-testing seepage and electromagnetic flux in a crack-porous matrix coupled system, specifically including the following steps: Step 1, Sample Preparation. Select the first and second porous matrix samples with corresponding interface roughness and permeability combinations according to the test objectives. Attach the waterproof acrylic sheet to the interface area where cracks are to be formed, assemble the T-shaped spacer strip, flow collection box, and silicone sealing gasket, and complete the overall resin casting to form an integrated sample assembly.

[0051] Step 2, Device Connection. Install the drive pump, inlet pipeline, upstream and downstream independent valves, three outlet beakers and electronic balance, upstream and downstream pressure sensors, and electromagnetic probe in sequence, and check the sealing and continuity of each connection.

[0052] Step 3, Boundary Setting. First, set the flow to single-crack test mode, only opening the upstream and downstream branches corresponding to the main crack channel and closing the matrix branch. After the single-crack flow test is completed, switch to the crack-matrix coupled flow test mode, opening the three downstream branches to obtain the coupling characteristics of the flow in the main crack channel and the exchange flow in the matrix.

[0053] Step 4, unidirectional water injection drive. Start the drive pump to continuously inject aqueous fluid into the sample inlet at the set flow rate. Tests can be conducted at multiple flow rates to study the flow response under different drive conditions. For a 5 mm crack opening, 20 mL / min, 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min, 500 mL / min, 800 mL / min, and 1000 mL / min can be selected as representative test flow rates.

[0054] Step 5, Hydraulic parameter acquisition. At each test flow rate level, after the flow reaches the preset stable condition, real-time data from three electronic balances and upstream and downstream pressure data are recorded. The outflow rate, total outflow rate, pressure drop, and pressure gradient are calculated for each channel. By comparing the magnitudes of Q1, Q2, and Q3, the flow characteristics of the main fracture channel and the degree of fracture-matrix exchange are analyzed. By comparing the pressure drop and flow splitting differences of different samples under the same injection conditions, the influence of the combination of interface roughness and matrix permeability on the coupled flow behavior is analyzed.

[0055] Step 6, Electromagnetic Response Acquisition. During the seepage process, the Proceq structural radar GP8800 is used to detect the sample surface. In real-time monitoring mode, electromagnetic responses are continuously acquired or acquired at set time intervals during the seepage process to track the migration of the water-air interface in the crack region. In steady-state monitoring mode, acquisition is performed after fluid breakthrough or after reaching the set steady-state conditions to analyze the differences in electromagnetic responses between the crack region and the adjacent matrix region under different flow states.

[0056] Step 7, Joint Analysis. The hydraulic data (flow rate, pressure difference, and pressure gradient) obtained from the seepage test are analyzed in conjunction with the electromagnetic detection results to establish the correlation between fracture structural state, flow exchange characteristics, local water content changes, and electromagnetic response.

[0057] Example 6: Typical Application In one typical application, two porous matrices with the same permeability level are selected and prepared as smooth, relatively rough, or rough interfaces, respectively, to compare the effects of changes in interface roughness on the flow in the main channel of the fracture, the flow exchange between the fracture and the matrix, and the electromagnetic response.

[0058] In another typical application, two porous matrices with different permeability levels are selected to form an asymmetric crack-matrix structure to analyze the influence of the permeability difference between the two matrices on the downstream diversion characteristics, exchange intensity and electromagnetic response distribution.

[0059] IV. Working Principle In the sample module, a fracture channel with a preset opening is formed between the first porous matrix sample and the second porous matrix sample. Under the action of the fluid injection and boundary control module, the aqueous fluid enters the sample from upstream under unidirectional drive. By adjusting the opening and closing states of the upstream and downstream valve assemblies, the fluid can be made to flow only along the main fracture channel, or the fluid can be made to exchange flow with the porous matrix on both sides while advancing along the main fracture channel. After the fluid enters the fracture, part of the fluid continues to move along the fracture direction and flows out through the fracture outlet branch, while the other part of the fluid seeps into the interior of the first and second porous matrix samples under the action of pressure difference and flows out through the corresponding matrix outlet branches, thus forming a split flow state downstream where the outflow from the main fracture channel and the outflow from the two matrix sides coexist. By independently acquiring the flow rates of the three outlets, the flow in the main fracture channel and the fracture-matrix exchange flow can be distinguished; by synchronously monitoring the upstream and downstream pressures, the pressure drop response and pressure gradient change law under different flow modes and different injection conditions can be obtained.

[0060] The principle of electromagnetic characterization lies in the fact that as the aqueous fluid propagates, remains, and exchanges within the fracture and adjacent matrix, the water content of the fracture region and the surrounding porous media continuously evolves, leading to changes in dielectric properties. High-frequency electromagnetic waves are sensitive to differences in the electrical properties of the medium and changes in the water content. When an electromagnetic probe is placed on the test surface of the sample and scans or probes the target area, electromagnetic response information related to the fracture location, the fluid state inside the fracture, and the fracture-matrix exchange process can be obtained. By correlating the electromagnetic response results with three-channel flow rate, pressure difference, and their time evolution, a synergistic characterization of the fracture interface state, flow channel characteristics, and local fluid distribution can be achieved.

[0061] In summary, through the different implementation methods described above, this application not only solves the problems of difficulty in distinguishing between fracture flow and matrix flow and the difficulty in simultaneously acquiring flow and detection information in traditional fracture seepage tests, but also provides a well-defined, boundary-controllable, and data-separately-acquired experimental equipment and testing method for the synergistic characterization of fracture interface states, fluid transport processes, and electromagnetic response characteristics. This application is applicable to the study of fracture-porous matrix coupling systems under various fracture interface states, matrix permeability combinations, and boundary control conditions, and has strong adaptability and scalability.

[0062] Although the embodiments of this application have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this application. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this application is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A co-current electromagnetic testing device for seepage in a fractured porous matrix coupled system, characterized in that, include: The sample module consists of a first porous matrix sample and a second porous matrix sample arranged opposite to each other, with a crack channel extending along the mainstream direction between the two porous matrix samples. The crack formation and end crack control module is located at the upstream and downstream ends of the sample module to maintain the preset opening of the crack channel and form the boundary basis for end flow acquisition. An integral sealing module is used to integrally cast and seal the periphery of the sample module to form an outer sealing structure that can withstand injection pressure. The fluid injection and boundary control module is used to provide unidirectional water-driven fluid to the crack channel and the first porous matrix sample and the second porous matrix sample on both sides of the crack channel and to switch different flow boundary modes. The outlet diversion acquisition module is located at the downstream end of the sample module. It consists of multiple independent external receiving acquisition structures and is used to independently export and collect the outflow of the crack channel and the porous matrix sample on both sides of the crack channel in real time. A pressure monitoring module is located in the upstream and downstream regions of the sample module to acquire pressure information at the injection end and the outlet end. An electromagnetic detection module is arranged on the external test surface of the overall sealing module to collect electromagnetic response information of the crack area and the adjacent substrate sample area.

2. The electromagnetic co-current testing device for seepage in a fractured porous matrix coupled system according to claim 1, characterized in that, The crack formation and end crack control module includes a T-shaped spacer strip disposed in the inlet and outlet area of ​​the crack channel. The T-shaped spacer strip is sandwiched between the first porous matrix sample and the second porous matrix sample to maintain a crack channel with a constant opening.

3. The electromagnetic co-testing device for seepage in a cracked porous matrix coupled system according to claim 2, characterized in that, The outlet diversion acquisition module includes three independent external receiving acquisition structures, corresponding to the outlet of the first porous matrix sample, the outlet of the crack channel, and the outlet of the second porous matrix sample, respectively.

4. The electromagnetic co-testing device for seepage in a cracked porous matrix coupled system according to claim 3, characterized in that, The outlet diversion acquisition module also includes: The flow collection box is connected to the end of the sample module and corresponds to the end region of the first porous matrix sample, the end region of the crack channel, and the end region of the second porous matrix sample, respectively. A silicone sealing gasket is disposed between the flow collection box and the end face of the sample module; The silicone sealing gasket and the bottom of the flow collection box are provided with a grooved air outlet and a flow guide to realize the independent flow and collection of the three fluids; the three outlet branches are respectively connected to a beaker and an electronic balance to monitor the flow rate of the three outlets in real time.

5. The electromagnetic co-testing device for seepage in a cracked porous matrix coupled system according to claim 4, characterized in that, The integral sealing module is formed by integrally casting and sealing the periphery of the sample module with resin material to form an integral resin sealing structure; before casting, a water-proof acrylic plate is pasted on the inner side of the crack channel to prevent resin from penetrating into the crack; the integral resin sealing structure covers the periphery of the first porous matrix sample and the second porous matrix sample, the outer side of the flow collection box at its end, and the periphery of the T-shaped spacer strip, and the inner side of the crack channel, the upstream and downstream surfaces of the first porous matrix sample and the second porous matrix sample, and the inlet and outlet areas of the crack channel are exposed outside the integral resin sealing structure.

6. The electromagnetic co-testing device for seepage in a fractured porous matrix coupled system according to claim 5, characterized in that, The fluid injection and boundary control module includes a liquid storage unit, a drive pump, an inlet pipeline, and independent valve assemblies located at the upstream and downstream ends. The independent valve assemblies control the opening and closing states of the first porous matrix sample branch, the fracture channel branch, and the second porous matrix sample branch, respectively, to achieve the switching between the single fracture flow mode and the fracture matrix coupled flow mode.

7. The electromagnetic co-testing device for seepage in a fractured porous matrix coupled system according to claim 6, characterized in that, The electromagnetic detection module is a transceiver integrated step-frequency continuous wave radar probe. When it is placed on the external test surface of the device, the electromagnetic wave propagation path passes sequentially through the resin integral sealing structure, the first porous matrix sample, the crack channel region, the second porous matrix sample, and the resin integral sealing structure outside the second porous matrix sample.

8. A method for electromagnetic co-current testing of seepage in a cracked porous matrix coupled system based on the device described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Prepare a first porous matrix sample and a second porous matrix sample, form a preset crack channel area between the two, assemble a crack formation and end crack control module and an outlet diversion and acquisition module, and then use an overall sealing module to cast and seal the periphery of the sample to form an integrated sample assembly. S2: Connect the fluid injection and boundary control module, pressure monitoring module, and electromagnetic detection module to the integrated sample assembly respectively; S3: Adjust the boundary control module according to the experimental purpose and set it to single-crack flow mode or crack-matrix coupled flow mode. S4: Start the drive pump to inject aqueous fluid into the sample inlet at a preset flow rate, forming a one-way water drive process; S5: During the fluid injection process, upstream pressure, downstream pressure, and multi-outlet flow data are collected in real time; S6: During the seepage process, the electromagnetic detection module is used to detect the target area of ​​the sample and obtain the electromagnetic response information of the crack area and the adjacent matrix area. S7: Jointly analyze the collected flow rate, pressure, and electromagnetic response data to establish the correspondence between fracture channel flow, fracture matrix exchange behavior, and interface electromagnetic characterization.

9. The method according to claim 8, characterized in that, In S3, the single-crack flow mode is: only the crack channel branch is opened upstream, only the crack channel branch outlet is opened downstream, and the two matrix sample branches are closed; the crack-matrix coupled flow mode is: the crack channel branch is opened upstream, and the outlets of the first porous matrix sample branch, the crack channel branch, and the second porous matrix sample branch are opened simultaneously downstream.

10. The method according to claim 8, characterized in that, In step S6, electromagnetic detection employs at least one of the following methods: Real-time monitoring method: Electromagnetic response is continuously collected or collected at set time intervals during the water drive process to track the dynamic evolution of the water-air interface inside the fracture. Steady-state point monitoring method: After the fluid breaks through or reaches a preset steady state, the sample is tested in a time-sharing manner to analyze the electromagnetic response characteristics corresponding to the fluid distribution state in the cracked double matrix structure.

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