3D Visualization Device and Method for Measuring Gas-Water Flow and Resistivity in Karst Caves

Abstract

This invention provides a three-dimensional visualization device and method for measuring the gas-water seepage and resistivity in karst caves. In this device, a three-dimensional visualization measurement model is mounted on a platform to prevent displacement. The three-dimensional visualization measurement model is a transparent model printed using 3D printing technology based on the karst cave core structure. Conductive metal mesh sheets, transparent fluid inlet / outlet channels, and transparent fluid conduit interfaces are respectively provided on its left and right sides. A constant fluid pump is used to inject fluid into the three-dimensional visualization measurement model. A fluid recovery device is used to collect the fluid flowing out of the three-dimensional visualization measurement model. A resistance measuring device is electrically connected to the conductive metal mesh sheets via wires to measure the resistivity of the three-dimensional visualization measurement model. A video recording device records the flow and distribution of fluid within the three-dimensional visualization measurement model. This invention can conduct three-dimensional visualization gas-water displacement experiments, achieving dynamic observation of gas-water seepage characteristics and resistivity measurement under the condition of considering the influence of fluid gravity.

Description

Technical Field

[0001] This invention relates to the field of natural gas exploration and development technology, and more specifically to a three-dimensional visualization device and method for measuring gas-water seepage and resistivity in karst caves. Background Technology

[0002] In the exploration and development of natural gas reservoirs, the study of gas-water two-phase flow and resistivity response characteristics is one of the core aspects of carbonate cavern reservoir evaluation. Since the 1930s, gas-water two-phase flow experiments have gradually gained attention from oil and gas exploration and development personnel. Early gas-water two-phase flow experiments used loose sand deposits or underground rock samples, injecting gas or water into the samples to simulate the gas-water two-phase flow characteristics of gas reservoirs. This method cannot directly observe the gas-water flow inside the rock; it can only indirectly infer the gas-water ratio inside the rock by measuring the fluid volume or weight at the outlet. Subsequently, based on gas-water two-phase flow experiments, rock resistivity measurement experiments based on real rock cores were developed.

[0003] In recent years, with the advancement of core testing techniques, two-dimensional visualization methods for measuring gas-water flow have been developed. This method is based on two-dimensional core slicing or two-dimensional glass engraving techniques, directly creating two-dimensional slices from the core or replicating the pore structure onto two-dimensional slices made of materials such as glass, before performing gas-water displacement and observation. While this method can visualize gas-water flow, the two-dimensional pore space differs significantly from the three-dimensional pore space of a real core, a difference particularly pronounced in cavernous reservoirs. This is because the size of the caverns in cavernous reservoirs is significantly larger than the pore size in conventional reservoirs, resulting in the gravitational influence on the fluid within the cavern being significantly stronger than the influence of surface tension. However, the observation sample prepared by the two-dimensional visualization gas-water flow measurement method is extremely thin, almost completely ignoring the influence of gravity, thus limiting the observation of gas-water flow in cavernous reservoirs. Therefore, there is an urgent need to design a three-dimensional visualization device for measuring gas-water flow and resistivity in cavernous reservoirs to address the shortcomings of existing gas-water two-phase flow and resistivity measurement techniques in terms of both visualization and the influence of fluid gravity. Summary of the Invention

[0004] The purpose of this invention is to provide a three-dimensional visualization device and method for measuring gas-water seepage and resistivity in karst caves. This device and method can conduct three-dimensional visualization gas-water displacement experiments and, under the condition of considering the influence of fluid gravity, realize dynamic observation of gas-water seepage characteristics and resistivity measurement, thereby obtaining the three-dimensional spatial distribution of gas and water in karst cave reservoirs at any water saturation state and the resistivity under the corresponding state.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A three-dimensional visualization device for measuring gas and water seepage and resistivity in karst caves includes: a three-dimensional visualization measurement model, a stage, a constant fluid pump, a resistance measuring device, a fluid recovery device, and a video recording device;

[0007] The three-dimensional visualization measurement model is set on the platform;

[0008] The stage is used to fix the three-dimensional visualization measurement model and prevent the three-dimensional visualization measurement model from shifting.

[0009] The three-dimensional visualization measurement model is a transparent model printed using 3D printing technology based on the rock core cave structure. The left and right sides of the three-dimensional visualization measurement model are respectively provided with conductive metal mesh, transparent fluid inlet and outlet channels and transparent fluid conduit interfaces. The conductive metal mesh is externally connected to wires, the transparent fluid inlet and outlet channels are connected to the transparent fluid conduit interfaces, and the transparent fluid conduit interfaces are externally connected to fluid conduits.

[0010] The constant fluid pump is connected to a transparent fluid conduit interface via a fluid conduit for injecting fluid into the three-dimensional visualization measurement model;

[0011] The fluid recovery device is connected to another transparent fluid conduit via a fluid conduit interface, and is used to collect the fluid flowing out of the three-dimensional visualization measurement model;

[0012] The resistance measuring device is electrically connected to the conductive metal mesh through a wire and is used to measure the resistivity of the three-dimensional visualization measurement model;

[0013] The video recording device is used to record the flow and distribution of fluid in a three-dimensional visualization measurement model from multiple perspectives.

[0014] Furthermore, the left side of the three-dimensional visualization measurement model is the fluid injection side, and the constant fluid pump is connected to the transparent fluid conduit interface on the left side of the three-dimensional visualization measurement model through a fluid conduit;

[0015] The right side of the three-dimensional visualization measurement model is the fluid outflow side, and the fluid recovery device is connected to the transparent fluid conduit interface on the right side of the three-dimensional visualization measurement model through a fluid conduit.

[0016] Furthermore, video recording devices are respectively installed above and in front of the three-dimensional visualization measurement model, so that the cave area of ​​the three-dimensional visualization measurement model is completely in the center of the video recording field of view and the captured images are clear and non-overlapping;

[0017] The two recording devices record the fluid flow and distribution in the three-dimensional visualization measurement model from both frontal and top-down views.

[0018] Furthermore, the method for preparing the three-dimensional visualization measurement model includes the following steps:

[0019] Extraction of core cave space: After CT scanning of the cores in the study area, image processing technology was used to obtain the skeleton and cave structure data of the cores, and representative core cave structures were selected and extracted into a cubic area to obtain the cubic core cave space.

[0020] Printing a transparent cave area: Using a cubic core cave space as a template, a transparent and pressure-resistant material is used to print a transparent cave area using 3D printing technology. The transparent cave area contains the core cave structure.

[0021] Fabrication of conductive metal mesh: Fabricate a conductive metal mesh with the same lateral area as the transparent cave area, with a portion extending from the top of the conductive metal mesh as an electrode for connection with a wire;

[0022] Print transparent fluid inlet / outlet channel: Use the same transparent pressure-resistant material as the transparent cave area to make a transparent fluid inlet / outlet channel. One side of the transparent fluid inlet / outlet channel has the same side area as the transparent cave area, and the other side has a hollow cylindrical channel of a certain length.

[0023] Print transparent fluid conduit interface: Use the same transparent pressure-resistant material as the transparent cave area to make the transparent fluid conduit interface. The transparent fluid conduit interface is a hollow cylinder. Its outer diameter is the same as the diameter of the hollow cylindrical channel of the transparent fluid inlet and outlet channel, and its inner diameter is the same as the size of the fluid conduit to ensure that it can be connected to the fluid conduit.

[0024] Assemble the three-dimensional visualization measurement model: Assemble conductive metal mesh sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces on the left and right sides of the transparent cave area to obtain a completely sealed and transparent three-dimensional visualization measurement model.

[0025] On the other hand, the present invention also provides a three-dimensional visualization method for measuring gas-water seepage and resistivity in karst caves, applied to the aforementioned three-dimensional visualization device for measuring gas-water seepage and resistivity in karst caves, comprising the following steps:

[0026] Based on the core karst cave structure of the study area, a transparent three-dimensional visualization measurement model was printed using transparent pressure-resistant material and 3D printing technology. The three-dimensional visualization measurement model includes a transparent karst cave area and conductive metal mesh sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces assembled on the left and right sides of the transparent karst cave area, respectively.

[0027] The three-dimensional visualization measurement model was assembled into a three-dimensional visualization device for measuring gas-water seepage and resistivity in karst caves.

[0028] A gas-water displacement experiment was conducted using a colored salt solution. Based on the images of the salt solution distribution in the frontal and top views captured by a video recording device, the water saturation of the salt solution under the distribution state was obtained.

[0029] The resistance of a three-dimensional visualization measurement model under a certain water saturation state is obtained by using a resistance measuring device, and the corresponding resistivity is obtained by conversion through a pre-measured resistivity scale coefficient K.

[0030] Furthermore, the gas-water displacement experiment using a colored salt solution, based on images of the salt solution distribution from both the frontal and top-down views captured by a video recording device, yields the water saturation of the salt solution under this distribution state. Specifically, this includes:

[0031] Core porosity is calculated using formula (1):

[0032]

[0033] In the formula, Core porosity, %; px pore The pixel count (px) represents the number of pixels corresponding to the core cavity structure obtained during the core cavity spatial extraction process; it is dimensionless. ma The number of pixels in the known core skeleton is dimensionless.

[0034] Based on the images of the salt solution distribution in the frontal and top-down directions captured by the video recording device, the number of pixels in the rock core cave structure occupied by the salt solution is calculated, and then the water saturation under this salt solution distribution state is calculated using formula (2):

[0035]

[0036] In the formula, Sw represents the water saturation level, in %; px w The number of pixels representing the core cavity structure occupied by salt solution, dimensionless; px pore The number of pixels corresponding to the core cave structure is dimensionless.

[0037] Furthermore, the method for measuring the resistivity scale coefficient K is as follows:

[0038] Using the same transparent printing material as the three-dimensional visualization measurement model, a three-dimensional visualization scale model is prepared by 3D printing technology. The transparent hollow area of ​​the three-dimensional visualization scale model is a hollow cube structure with the same external dimensions as the three-dimensional visualization measurement model. The hollow cube structure is the largest inscribed cube of the transparent cave area of ​​the three-dimensional visualization measurement model. The left and right sides of the hollow cube structure are assembled with the same conductive metal mesh, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces as the three-dimensional visualization measurement model.

[0039] Replace the three-dimensional visualization measurement model with a three-dimensional visualization scale model and assemble it into a three-dimensional visualization device for measuring gas and water seepage and resistivity in karst caves.

[0040] After completely filling the 3D visualization scale model with salt solution, the resistance of the 3D visualization scale model is measured using a resistance measuring device. Given the resistivity of the salt solution, the ratio of the two is the resistivity calibration coefficient K, expressed by the formula:

[0041]

[0042] In the formula, K is the resistivity calibration coefficient, m; R w The resistivity of the salt solution is given by r in Ω·m. c The resistance, in Ω, was measured using a three-dimensional visual scale model after the model was completely filled with salt solution.

[0043] Furthermore, the formula for calculating the resistivity of the three-dimensional visualization measurement model is as follows:

[0044] R m =K×r m (4)

[0045] In the formula, R m Resistivity of the three-dimensional visualization measurement model at the same water saturation level, in Ω·m; K is the resistivity calibration coefficient, in m; r m The resistance, in Ω, is the resistance of a three-dimensional visualization measurement model under a certain water saturation state.

[0046] According to specific embodiments provided by the present invention, the following technical effects are disclosed: The three-dimensional visualization device and method for measuring gas-water seepage and resistivity in karst caves provided by the present invention includes a three-dimensional visualization measurement model, a stage, a constant fluid pump, a resistance measurement device, a fluid recovery device, and a video recording device; wherein, the three-dimensional visualization measurement model is a transparent model based on the karst cave structure in a rock core, printed using 3D printing technology, which can be used to simulate the three-dimensional spatial structure of a real karst cave reservoir. Using this device to conduct gas-water displacement experiments, the three-dimensional spatial distribution of gas and water in a karst cave reservoir under any water saturation state and the resistivity under the corresponding state can be obtained.

[0047] For core samples from carbonate cavern reservoirs, existing rock electrical experiments can easily obtain their resistivity response, but cannot observe the gas-water seepage state within the cavern space. The device provided by this invention can simultaneously observe the gas-water seepage characteristics within the cavern space while simulating the gas-water seepage and resistivity measurement process.

[0048] Existing visualization displacement models can observe the gas-water seepage state of samples, but most samples are based on two-dimensional cave structures extracted from core two-dimensional photographs, which are very different from the real cave structures. This invention is based on 3D printing technology, which extracts the real three-dimensional cave structure and prepares a transparent model with the same cave space. Combined with simulated gas-water seepage and resistivity measurement experiments, after data conversion, it can reflect the seepage characteristics and resistivity response characteristics of the cave reservoir. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structure of the three-dimensional visualization device for measuring the gas-water seepage and resistivity in karst caves according to the present invention;

[0051] Figure 2 This is a schematic diagram of the three-dimensional visualization measurement model of the present invention, wherein A represents the assembly diagram and B represents the exploded view;

[0052] Figure 3 This is a schematic diagram of the three-dimensional visualization scale model of the present invention, wherein A represents the assembly diagram and B represents the exploded view;

[0053] Figure 4 This is a schematic diagram of the transparent cutout area of ​​the three-dimensional visualization measurement model in an embodiment of the present invention, wherein A represents the front view, B represents the top view, C represents the left side view, and D represents the right side view;

[0054] Figure 5 This is a schematic diagram of the resistivity metal mesh structure in an embodiment of the present invention, wherein A represents the left resistivity metal mesh and B represents the right resistivity metal mesh; taking the left resistivity metal mesh as an example, A-1 represents the front view, A-2 represents the top view, A-3 represents the side view, and A-4 represents the enlarged view of the mesh.

[0055] Figure 6 This is a schematic diagram of the transparent fluid inlet / outlet channel structure in an embodiment of the present invention. In the diagram, A represents the left transparent fluid inlet / outlet channel and B represents the right transparent fluid inlet / outlet channel. Taking the left transparent fluid inlet / outlet channel as an example, A-1 represents the front view, A-2 represents the top view, A-3 represents the left side view, and A-4 represents the right side view.

[0056] Figure 7This is a schematic diagram of the transparent fluid conduit interface structure in an embodiment of the present invention, wherein A represents the left fluid conduit interface and B represents the right fluid conduit interface; taking the left fluid conduit interface as an example, A-1 represents the front view, A-2 represents the top view, A-3 represents the left side view, and A-4 represents the right side view;

[0057] Figure 8 This is a schematic diagram of the three-dimensional visualization scale model structure in an embodiment of the present invention, wherein A represents the front view, B represents the top view, C represents the left side view, and D represents the right side view;

[0058] Explanation of reference numerals in the attached drawings: 1. Three-dimensional visualization measurement model; 2. Stage; 3. Constant fluid pump; 4. Resistance measuring device; 5. Fluid recovery device; 6. Video recording device; 7. Fluid conduit; 8. Wire;

[0059] 1-1. Transparent cavern area; 1-2. Conductive metal mesh sheet; 1-3. Transparent fluid inlet / outlet channel; 1-4. Transparent fluid conduit interface;

[0060] 1-1', Transparent hollow area; 1-2-1, Grid area; 1-2-2, Electrode; 1-3-1, Irregular hexahedral hollow channel; 1-3-2, Hollow cylinder. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] This invention addresses the shortcomings of existing gas-water two-phase flow and resistivity measurement technologies in terms of visualization and the influence of fluid gravity. It provides a three-dimensional visualization device for measuring gas-water flow and resistivity in karst reservoirs. Using this device to conduct gas-water displacement experiments, the three-dimensional spatial distribution of gas and water in karst reservoirs at any water saturation level and the resistivity under the corresponding conditions can be obtained.

[0063] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0064] like Figure 1 and Figure 2 As shown, the three-dimensional visualization device for measuring gas and water seepage and resistivity in karst caves provided by the present invention includes: a three-dimensional visualization measurement model 1, a stage 2, a constant fluid pump 3, a resistance measuring device 4, a fluid recovery device 5, and a video recording device 6.

[0065] The three-dimensional visualization measurement model 1 is set on the stage 2;

[0066] The stage 2 is used to fix the three-dimensional visualization measurement model 1 and prevent the three-dimensional visualization measurement model 1 from shifting.

[0067] The three-dimensional visualization measurement model 1 is a transparent model printed using 3D printing technology based on the core cave structure. The transparent model includes a transparent cave area, which contains the core cave structure. The left and right sides of the three-dimensional visualization measurement model 1 are respectively provided with a conductive metal mesh sheet 1-2, a transparent fluid inlet / outlet channel 1-3, and a transparent fluid conduit interface 1-4. The conductive metal mesh sheet 1-2 is externally connected to a wire 8. The transparent fluid inlet / outlet channel 1-3 is connected to the transparent fluid conduit interface 1-4. The transparent fluid conduit interface 1-4 is externally connected to a fluid conduit 7.

[0068] The left side of the three-dimensional visualization measurement model 1 is the fluid injection side. The constant fluid pump 3 is connected to the transparent fluid conduit interface 1-4 on the left side of the three-dimensional visualization measurement model 1 through the fluid conduit 7, and is used to inject fluid into the three-dimensional visualization measurement model; for example, the fluid is a gas or a salt solution.

[0069] The right side of the three-dimensional visualization measurement model 1 is the fluid outflow side. The fluid recovery device 5 is connected to the transparent fluid conduit interface 1-4 on the right side of the three-dimensional visualization measurement model 1 through the fluid conduit 7, and is used to collect the fluid flowing out of the three-dimensional visualization measurement model for recycling.

[0070] The resistance measuring device 4 is electrically connected to the conductive metal mesh 1-2 via a wire 8, and is used to measure the resistivity of the three-dimensional visualization measurement model 1;

[0071] The video recording device 6 is used to record the flow and distribution of fluid in the three-dimensional visualization measurement model 1 from multiple perspectives (e.g., frontal and top views);

[0072] The fluid conduit 7 connects the constant fluid pump 3, the fluid recovery device 5, and the three-dimensional visualization measurement model 1, and is used to transport fluid; the wire 8 connects the resistance measuring device 4 and the three-dimensional visualization measurement model 1, and is used to measure the resistivity of the three-dimensional visualization measurement model 1.

[0073] Specifically, video recording devices 6 are respectively set above and in front of the three-dimensional visualization measurement model 1, so that the cave area of ​​the three-dimensional visualization measurement model is completely in the center of the video recording field of view and the captured images are clear and non-overlapping;

[0074] The two recording devices 6 record the fluid flow and distribution in the three-dimensional visualization measurement model 1 from the front view and top view, respectively.

[0075] Specifically, such as Figure 2 As shown, the method for preparing the three-dimensional visualization measurement model 1 includes the following six steps:

[0076] ① Extraction of rock cores from karst cave spaces:

[0077] After CT scanning of the rock cores in the study area, image processing technology was used to obtain the skeleton and cave structure data of the rock cores. Then, representative cave structure areas were selected and extracted into a cubic area to obtain the cubic-shaped rock core cave space.

[0078] ② Printing of transparent cave areas:

[0079] Using the aforementioned cubic-shaped core cave space as a template, transparent pressure-resistant material was used to print the transparent cave area 1-1 using 3D printing technology;

[0080] ③ Fabrication of conductive metal mesh sheets:

[0081] Select a highly conductive metal material (gold, copper, aluminum alloy, etc.) and process it into a thin conductive metal mesh sheet 1-2 with the same lateral area as the transparent cave area. The mesh density inside the conductive metal mesh sheet 1-2 must be appropriate; that is, the conductive metal mesh sheet 1-2 must be in contact with the fluid, but not completely block the inflow and outflow of the fluid. Furthermore, a portion of the top of the conductive metal mesh sheet 1-2 must extend out as an electrode for connection to the wire 8.

[0082] ④ Printing of transparent fluid inlet / outlet channels:

[0083] Using the same transparent pressure-resistant material as the transparent cave area, transparent fluid inlet and outlet channels 1-3 are made. One side of the transparent fluid inlet and outlet channels 1-3 has the same lateral area as the transparent cave area, while the other side has a hollow cylindrical channel of a certain length.

[0084] ⑤ Printing of transparent fluid conduit interfaces:

[0085] Using the same transparent pressure-resistant material as the transparent cave area, transparent fluid conduit interfaces 1-4 are made. Transparent fluid conduit interfaces 1-4 are hollow cylinders with an outer diameter that is the same as the diameter of the hollow cylindrical channel of the transparent fluid inlet and outlet channel, and an inner diameter that is the same as the size of the fluid conduit, to ensure that the fluid conduit 7 can be connected.

[0086] ⑥ Assembly of 3D visualization measurement model:

[0087] Using techniques such as thermocompression bonding, micro-encapsulation bonding, or precision adhesive bonding, the transparent cavity region 1-1, conductive metal mesh sheet 1-2, transparent fluid inlet / outlet channel 1-3, and transparent fluid conduit interface 1-4 of the aforementioned components are assembled together. The contact areas between the components must be completely sealed and kept transparent, ultimately resulting in a three-dimensional visualization measurement model, such as... Figure 2 As shown in Figure A.

[0088] On the other hand, the present invention also provides a three-dimensional visualization method for measuring gas-water seepage and resistivity in karst caves, applied to the aforementioned three-dimensional visualization device for measuring gas-water seepage and resistivity in karst caves, comprising the following steps:

[0089] S1. Based on the core cave structure of the study area, a transparent three-dimensional visualization measurement model was printed using transparent pressure-resistant material and 3D printing technology. The three-dimensional visualization measurement model includes a transparent cave area and conductive metal mesh sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces assembled on the left and right sides of the transparent cave area, respectively.

[0090] The specific preparation method of the three-dimensional visualization measurement model is as described above, consisting of six steps.

[0091] S2, assemble the three-dimensional visualization measurement model into the three-dimensional visualization karst cave gas-water seepage and resistivity measurement device;

[0092] S3, a gas-water displacement experiment was conducted using a colored salt solution. Based on images of the salt solution distribution from the front and top views captured by a video recording device, the water saturation under this salt solution distribution state was obtained. Specifically, the porosity and water saturation were calculated as follows:

[0093] During the extraction of karst cave space from rock cores, the number of pixels (px) corresponding to the actual karst cave space structure in the rock core can be obtained. pore ), and the number of pixels (px) corresponding to the core skeleton is known. ma The core porosity can be calculated using formula (1):

[0094]

[0095] In the formula, Core porosity, %; px pore px represents the number of pixels in the cave, dimensionless. ma The number of pixels in the core skeleton is dimensionless.

[0096] By using salt solutions of a specific color for gas-water displacement experiments, the distribution of the salt solution within the cavern space of a three-dimensional visualization measurement model can be easily observed. Based on images of the salt solution distribution taken from the frontal and top-down views using a video recording device, the number of pixels (px) occupying the cavern space by the salt solution can be calculated. w Then, the water saturation (Sw) of the salt solution distribution state can be calculated using formula (2):

[0097]

[0098] In the formula, Sw represents the water saturation level, in %; px w px represents the number of pixels in the salt solution, dimensionless. pore The number of pixels in the core karst cave is dimensionless.

[0099] S4. Using a resistance measuring device, the resistance corresponding to a three-dimensional visualization measurement model under a certain water saturation state is obtained, and the corresponding resistivity is obtained by conversion through a pre-measured resistivity scale coefficient K.

[0100] The method for measuring the resistivity calibration coefficient K is as follows:

[0101] like Figure 3 As shown, a three-dimensional visualization scale model is prepared using the same transparent printing material as the three-dimensional visualization measurement model and 3D printing technology. The transparent hollow area 1-1' of the three-dimensional visualization scale model is a hollow cube structure, as shown. Figure 4 As shown, its external dimensions are the same as those of the three-dimensional visualization measurement model. The hollow cube structure is the largest inscribed cube of the transparent cave area of ​​the three-dimensional visualization measurement model. The left and right sides of the hollow cube structure are equipped with the same conductive metal mesh, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces as those of the three-dimensional visualization measurement model.

[0102] Replace the three-dimensional visualization measurement model with a three-dimensional visualization scale model and assemble it into a three-dimensional visualization device for measuring gas and water seepage and resistivity in karst caves.

[0103] After completely filling the 3D visualization scale model with salt solution, the resistance of the 3D visualization scale model is measured using a resistance measuring device. Given the resistivity of the salt solution, the ratio of the two is the resistivity calibration coefficient K, expressed by the formula:

[0104]

[0105] In the formula, K is the resistivity calibration coefficient, m; R w The resistivity of the salt solution is given by r in Ω·m. c The resistance, in Ω, was measured using a three-dimensional visual scale model after the model was completely filled with salt solution.

[0106] Using a resistance measuring device, the resistance r corresponding to a three-dimensional visualization measurement model under a certain water saturation state is obtained. m Then, using formula (4), the resistivity R corresponding to the three-dimensional visualization measurement model under this water saturation state is obtained. m ; Resistivity (R) of a three-dimensional visualization measurement model m This can be approximated by the true resistivity of the core (R). t The formula for calculating the resistivity of the three-dimensional visualization measurement model is as follows:

[0107] R m =K×r m (4)

[0108] In the formula, R m Resistivity of the three-dimensional visualization measurement model at the same water saturation level, in Ω·m; K is the resistivity calibration coefficient, in m; r m The resistance, in Ω, is the resistance of a three-dimensional visualization measurement model under a certain water saturation state.

[0109] The significance of the aforementioned three-dimensional visualization scale model is as follows:

[0110] The raw experimental data obtained from the 3D visualization measurement model is resistance, which needs to be converted to resistivity using a resistivity scale factor K. The resistivity scale factor K is related to the structure of the 3D visualization measurement model and can be obtained through the 3D visualization scale model. For a fixed-size 3D visualization measurement model, only one 3D visualization scale model of the same size needs to be made. Under constant external conditions, the resistivity scale factor K of the same 3D visualization measurement model remains constant; therefore, the resistivity (R) of the salt solution only needs to be measured once in the entire experiment. w ) and the resistance of the calibrated model completely filled with salt solution (r c This avoids the tedious process of measuring resistivity in salt solutions and three-dimensional visualization scale models.

[0111] Structure and preparation of the three-dimensional visualization scale model:

[0112] like Figure 3 As shown, a three-dimensional visualization scale model was prepared using the same transparent printing material as the transparent cave area. The difference between the three-dimensional visualization measurement model and the three-dimensional visualization scale model sample is that the transparent hollow area of ​​the three-dimensional visualization scale model sample is a hollow cube structure. Its external dimensions are the same as those of the three-dimensional visualization measurement model, while its internal dimensions are the largest inscribed cube of the cave space in the three-dimensional visualization measurement model. All other parts are exactly the same. Furthermore, the parts are assembled according to the same combination techniques and requirements as the three-dimensional visualization measurement model to finally obtain the three-dimensional visualization scale model.

[0113] Example

[0114] The specific embodiments of the three-dimensional visualization method for measuring gas-water seepage and resistivity in karst caves described in this invention are as follows:

[0115] (1) Preparation and structure of three-dimensional visualization measurement model

[0116] Complete the preparation of the three-dimensional visualization measurement model by following the aforementioned six steps.

[0117] ① Core extraction from karst caves

[0118] Core samples from a karst-type carbonate reservoir in a certain region were selected. After CT scanning, a core data area measuring 4cm in length, 4cm in width, and 4cm in height was extracted. Image processing techniques were used to obtain the core's framework and karst structure data. After segmenting out representative karst structures, they were extracted to the center of a cubic region measuring 4cm in length, 6cm in width, and 6cm in height, thus obtaining a cubic karst space.

[0119] ② Printing of transparent cave areas

[0120] Using the aforementioned cubic cave space as a template, and employing transparent, pressure-resistant material, a transparent cave area measuring 4cm in length, 6cm in width, and 6cm in height was printed using 3D printing technology. Figure 4 Part 1-1.

[0121] ③ Fabrication of conductive metal mesh sheets

[0122] like Figure 5 As shown, copper is chosen as the material for the conductive metal. First, a conductive metal sheet is made, 6cm long, 8cm high, and 0.05cm thick. Then, the conductive metal sheet is cut and processed, extending 3cm inwards from the top edge, and then extending 1cm inwards from the remaining three edges. Each individual grid strip is 4cm long, 0.2cm wide, and 0.05cm thick. The overall area is a grid region of 4cm long, 4cm wide, and 0.05cm thick (e.g., ...). Figure 5 Part 1-2-1), and allows the mesh to contact the fluid without completely blocking its inflow and outflow; a 1cm long, 2cm high, and 0.05cm thick section is cut from the center of the upper edge of the metal sheet to serve as an electrode. Figure 5 Parts 1-2-2) are used to obtain the final conductive metal mesh sheet. Figure 5 Parts 1-2).

[0123] ④ Printing of transparent fluid inlet / outlet channels

[0124] like Figure 6As shown, the same transparent pressure-resistant material as the transparent cave area is used to construct the transparent fluid inlet / outlet channel 1-3. The transparent fluid inlet / outlet channel 1-3 has a total length of 2cm, a width of 6cm, and a height of 6cm. One side of the interior is an irregular hexahedral hollow channel 1-3-1 with a central circle of 1cm in diameter and a central rectangle of 4cm in length and 4cm in width as the top and bottom bases and a height of 1.5cm. At the same time, the other side of the interior has a hollow cylindrical channel of a certain length, which is a hollow cylinder 1-3-2 with a diameter of 1cm and a length of 0.5cm.

[0125] ⑤ Printing of transparent fluid conduit interfaces

[0126] like Figure 7 As shown, transparent fluid conduit interfaces 1-4 are fabricated using the same transparent pressure-resistant material as the transparent cave area. Transparent fluid conduit interfaces 1-4 are hollow cylinders with an outer diameter of 1 cm, an inner diameter of 0.6 cm, and a length of 2 cm.

[0127] ⑥ Assembly of 3D Visualization Measurement Model

[0128] Using high-temperature bonding technology, the above parts are assembled according to... Figure 2 As shown in Figure B, the parts are assembled from left to right to ensure that the contact areas between the parts are completely sealed; all channels and areas printed are unobstructed and remain transparent, ultimately resulting in a three-dimensional visualization measurement model.

[0129] (2) Structure and preparation of three-dimensional visualization scale model

[0130] like Figure 8 As shown, a three-dimensional visualization scale model was created using the same transparent pressure-resistant material as the transparent cave area. The difference between the three-dimensional visualization measurement model and the three-dimensional visualization scale model lies in the fact that the transparent hollow area 1-1' of the three-dimensional visualization scale model is a hollow cube structure. Its outer cube dimensions are 4cm, width 6cm, and height 6cm, while the inner hollow cube dimensions are 4cm, width 4cm, and height 4cm. All other parts are identical. Furthermore, using the same bonding techniques and requirements as the three-dimensional visualization measurement model, all parts are assembled according to… Figure 3 As shown in Figure B, the various parts are assembled to obtain a three-dimensional visualization scale model.

[0131] (3) Assembly structure

[0132] according to Figure 1The diagram shows the setup for simulating gas-water seepage and resistivity measurement in a karst cave reservoir. The stage 2 is horizontally fixed, and the 3D visualization measurement model 1 is fixed at the center of stage 2. A constant fluid pump 3 is connected to an external fluid conduit 7, which is then connected to the fluid conduit interface in the fluid inlet area of ​​the 3D visualization measurement model 1. Similarly, a fluid recovery device 5 is also connected to an external fluid conduit, which is then connected to the fluid conduit interface in the fluid outlet area of ​​the 3D visualization measurement model. One end of a wire 8 is connected to the resistance measuring device 4, and the other end is clamped to the electrode of the conductive metal mesh in the 3D visualization measurement model 1. Recording devices 6 are installed directly above and in front of the 3D visualization measurement model 1, ensuring that the karst cave area of ​​the 3D visualization measurement model is completely centered in the recording field of view and that the captured images are clear and non-overlapping. During the experiment, to determine the resistivity calibration coefficient K, the 3D visualization measurement model can be replaced with a 3D visualization calibration model, with the same connection method.

[0133] (4) Measurement data processing

[0134] ① Calculation of porosity and water saturation

[0135] During the extraction of karst cave space from rock cores, the number of pixels (px) corresponding to the actual karst cave space structure in the rock core can be obtained. pore =28590396), and the number of pixels (px) corresponding to the core skeleton is known. ma =775766604), the core porosity can be calculated using formula (5). (Round to three decimal places):

[0136]

[0137] In the formula, Core porosity, %; px pore px represents the number of pixels in the cave, dimensionless. ma The number of pixels in the core skeleton is dimensionless.

[0138] By selecting a salt solution of a specific color for the gas-water displacement experiment, the distribution of the salt solution within the cavern space of the three-dimensional visualization measurement model can be easily observed. Based on the images of the salt solution distribution taken from the front and top views using a video recording device, the number of pixels (px) occupying the cavern space by the salt solution can be calculated. w =16060860), and then the water saturation of the salt solution under the distribution state can be calculated by formula (6) (Sw is rounded to three decimal places):

[0139]

[0140] In the formula, Sw represents the water saturation level, in %; pxw px represents the number of pixels in the salt solution, dimensionless. pore The number of pixels in the core karst cave is dimensionless.

[0141] ② Determination of resistivity scale factor K

[0142] After completely filling the three-dimensional visualization scale model with salt solution, the resistance (r) of the three-dimensional visualization scale model was measured using a resistance measuring device. c =2.304Ω); and the resistivity of the salt solution (R) is known. w =0.053Ω.m), the ratio of the two is the resistivity scale coefficient K, which is expressed by formula (7):

[0143]

[0144] In the formula, K is the resistivity calibration coefficient, m; R w The resistivity of the salt solution is given by r in Ω·m. c The resistance, in Ω, of a three-dimensional visualized scale model after the surface is completely filled with salt solution.

[0145] ③ Three-dimensional visualization measurement model resistivity R m Sure

[0146] Using a resistance measuring device, the resistance (r) corresponding to the three-dimensional visualization measurement model under the water saturation state obtained by formula (6) is obtained. m =581.164Ω); then using formula (8), the resistivity (R) corresponding to the three-dimensional visualization measurement model under this water saturation state is obtained. m (Retain three decimal places); resistivity (R) of a three-dimensional visualization measurement model. m This can be approximated by the true resistivity of the core (R). t ).

[0147] R m =K×r m =0.023 × 581.164 = 13.367 (8)

[0148] In the formula, R m Resistivity of the three-dimensional visualization measurement model at the same water saturation level, in Ω·m; K is the resistivity calibration coefficient, in m; r m The resistance, in Ω, is the resistance of a three-dimensional visualization measurement model under a certain water saturation state.

[0149] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A three-dimensional visualization method for measuring the seepage and resistivity of gas and water in karst caves, characterized in that, The device is applied to the measurement of gas and water seepage and resistivity in karst caves under three-dimensional visualization. The device includes: a three-dimensional visualization measurement model, a stage, a constant fluid pump, a resistance measurement device, a fluid recovery device, and a video recording device. The three-dimensional visualization measurement model is set on the platform; The stage is used to fix the three-dimensional visualization measurement model and prevent the three-dimensional visualization measurement model from shifting. The three-dimensional visualization measurement model is a transparent model printed using 3D printing technology based on the rock core cave structure. The left and right sides of the three-dimensional visualization measurement model are respectively provided with conductive metal mesh, transparent fluid inlet and outlet channels and transparent fluid conduit interfaces. The conductive metal mesh is externally connected to wires, the transparent fluid inlet and outlet channels are connected to the transparent fluid conduit interfaces, and the transparent fluid conduit interfaces are externally connected to fluid conduits. The constant fluid pump is connected to a transparent fluid conduit interface via a fluid conduit for injecting fluid into the three-dimensional visualization measurement model; The fluid recovery device is connected to another transparent fluid conduit via a fluid conduit interface, and is used to collect the fluid flowing out of the three-dimensional visualization measurement model; The resistance measuring device is electrically connected to the conductive metal mesh through a wire and is used to measure the resistance of the three-dimensional visualization measurement model; The video recording device is used to record the flow and distribution of fluid in a three-dimensional visualization measurement model from multiple perspectives; The measurement method of the three-dimensional visualization karst cave gas-water seepage and resistivity measurement device includes the following steps: Based on the core karst cave structure of the study area, a transparent three-dimensional visualization measurement model was printed using transparent pressure-resistant material and 3D printing technology. The three-dimensional visualization measurement model includes a transparent karst cave area and conductive metal mesh sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces assembled on the left and right sides of the transparent karst cave area, respectively. The three-dimensional visualization measurement model was assembled into a three-dimensional visualization device for measuring gas-water seepage and resistivity in karst caves. A gas-water displacement experiment was conducted using a colored salt solution. Based on the images of the salt solution distribution in the frontal and top views captured by a video recording device, the water saturation of the salt solution under the distribution state was obtained. Using a resistance measuring device, the resistance of a three-dimensional visualization measurement model under a certain water saturation state is obtained, and the resistance is then measured using a pre-measured resistivity calibration coefficient. K The corresponding resistivity is obtained by conversion; The formula for calculating the resistivity of the three-dimensional visualization measurement model is as follows: （4） In the formula, Resistivity, in Ω·m, of the three-dimensional visualization measurement model under the same water saturation. K The resistivity scale factor is m; The resistance, in Ω, of a three-dimensional visualization measurement model under a certain water saturation state; （3） In the formula, K The resistivity scale factor is m; ρ is the resistivity of the salt solution, in Ω·m; The resistance, in Ω, was measured using a three-dimensional visual scale model after the model was completely filled with salt solution.

2. The method for measuring the three-dimensional visualization of gas-water seepage and resistivity in karst caves according to claim 1, characterized in that, The left side of the three-dimensional visualization measurement model is the fluid injection side, and the constant fluid pump is connected to the transparent fluid conduit interface on the left side of the three-dimensional visualization measurement model through a fluid conduit. The right side of the three-dimensional visualization measurement model is the fluid outflow side, and the fluid recovery device is connected to the transparent fluid conduit interface on the right side of the three-dimensional visualization measurement model through a fluid conduit.

3. The method for measuring the three-dimensional visualization of gas-water seepage and resistivity in karst caves according to claim 1, characterized in that, The recording devices are respectively set at the top and front of the three-dimensional visualization measurement model, so that the cave structure area of ​​the three-dimensional visualization measurement model is completely in the center of the recording field of view and the captured images are clear and non-overlapping; The two recording devices record the fluid flow and distribution in the three-dimensional visualization measurement model from both frontal and top-down views.

4. The method for measuring the three-dimensional visualization of gas-water seepage and resistivity in karst caves according to claim 1, characterized in that, The method for preparing the three-dimensional visualization measurement model includes the following steps: Extraction of core cave space: After CT scanning of the cores in the study area, image processing technology was used to obtain core skeleton and cave structure data, and representative core cave structures were selected and extracted into a cubic area to obtain a cubic core cave space; Printing a transparent cave area: Using a cubic core cave space as a template, a transparent and pressure-resistant material is used to print a transparent cave area using 3D printing technology. The transparent cave area contains the core cave structure. Fabrication of conductive metal mesh: Fabricate a conductive metal mesh with the same lateral area as the transparent cave area, with a portion extending from the top of the conductive metal mesh as an electrode for connection with a wire; Print transparent fluid inlet / outlet channel: Use the same transparent pressure-resistant material as the transparent cave area to make a transparent fluid inlet / outlet channel. One side of the transparent fluid inlet / outlet channel has the same side area as the transparent cave area, and the other side has a hollow cylindrical channel of a certain length. Print transparent fluid conduit interface: Use the same transparent pressure-resistant material as the transparent cave area to make the transparent fluid conduit interface. The transparent fluid conduit interface is a hollow cylinder. Its outer diameter is the same as the diameter of the hollow cylindrical channel of the transparent fluid inlet and outlet channel, and its inner diameter is the same as the size of the fluid conduit to ensure that it can be connected to the fluid conduit. Assemble the three-dimensional visualization measurement model: Assemble conductive metal mesh sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces on the left and right sides of the transparent cave area to obtain a completely sealed and transparent three-dimensional visualization measurement model.

5. The method for measuring the three-dimensional visualization of gas-water seepage and resistivity in karst caves according to claim 1, characterized in that, The gas-water displacement experiment using a colored salt solution, based on images of the salt solution distribution from both frontal and top-down views captured by a video recording device, yields the water saturation of the salt solution under this distribution state. Specifically, this includes: Core porosity is calculated using formula (1): （1） In the formula, The core porosity is %; The number of pixels corresponding to the core cavity structure obtained during the core cavity spatial extraction process is dimensionless. The number of pixels in the known core skeleton is dimensionless. Based on the images of the salt solution distribution in the frontal and top-down directions captured by the video recording device, the number of pixels in the rock core cave structure occupied by the salt solution is calculated, and then the water saturation under this salt solution distribution state is calculated using formula (2): （2） In the formula, Sw The water saturation level is %; The number of pixels representing the core cavity structure occupied by salt solution, dimensionless; The number of pixels corresponding to the core karst cave structure is dimensionless.

6. The method for measuring the three-dimensional visualization of gas-water seepage and resistivity in karst caves according to claim 1, characterized in that, The resistivity scale coefficient K The measurement method is as follows: Using the same transparent printing material as the three-dimensional visualization measurement model, a three-dimensional visualization scale model is prepared by 3D printing technology. The transparent hollow area of ​​the three-dimensional visualization scale model is a hollow cube structure with the same external dimensions as the three-dimensional visualization measurement model. The hollow cube structure is the largest inscribed cube of the transparent cave area of ​​the three-dimensional visualization measurement model. The left and right sides of the hollow cube structure are assembled with the same conductive metal mesh, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces as the three-dimensional visualization measurement model. Replace the three-dimensional visualization measurement model with a three-dimensional visualization scale model and assemble it into a three-dimensional visualization device for measuring gas and water seepage and resistivity in karst caves. After completely filling the 3D visualization scale model with salt solution, the resistance of the 3D visualization scale model is measured using a resistance measuring device. Since the resistivity of the salt solution is known, the ratio of the two is the resistivity calibration coefficient. K .

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