Three-dimensional visual karst cave gas-water seepage and resistivity measuring device and method

Abstract

The invention provides a three-dimensional visual karst cave gas-water seepage and resistivity measurement device and method, and the device is characterized in that a three-dimensional visual measurement model is arranged on an objective table, and is prevented from deviating; the three-dimensional visual measurement model is a transparent model obtained by printing through a 3D printing technology based on a rock core karst cave structure, and the left side and the right side of the three-dimensional visual measurement model are respectively provided with a conductive metal grid sheet, a transparent fluid access channel and a transparent fluid conduit interface; the constant fluid pump is used for injecting fluid into the three-dimensional visual measurement model; the fluid recovery device is used for collecting fluid flowing out of the three-dimensional visual measurement model; the resistance measuring device is electrically connected with the conductive metal grid sheet through a wire, and is used for measuring the resistivity of the three-dimensional visual measurement model; and the video recording device records the flowing and distribution conditions of the fluid in the three-dimensional visual measurement model. According to the invention, a three-dimensional visual gas-water displacement experiment can be carried out, and gas-water seepage characteristic dynamic observation and resistivity measurement are realized under the condition of considering the influence of fluid gravity.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas exploration and development, and more specifically, to a three-dimensional visualization device and method for gas-water seepage and resistivity measurement in karst caves. Background Art

[0002] During the exploration and development of natural gas reservoirs, the study of the gas-water two-phase seepage and resistivity response characteristics is one of the cores of carbonate karst reservoir evaluation. Since the 1930s, gas-water two-phase seepage experiments have gradually attracted the attention of oil and gas exploration and development personnel. In the early gas-water two-phase seepage experiments, loose sand grain accumulations or underground rock samples were used, and gas or water was injected into the samples to simulate the gas-water two-phase seepage characteristics of gas reservoirs. This method could not directly observe the gas-water seepage inside the rock, and could only indirectly infer the gas-water ratio inside the rock by measuring the volume or weight of the fluid at the outlet end. Subsequently, based on the gas-water two-phase seepage experiment, a rock resistivity measurement experiment based on real cores was developed.

[0003] In recent years, with the progress of core experiment technology, a two-dimensional visualization gas-water seepage measurement method has been developed. This method is based on two-dimensional core slices or two-dimensional glass engraving technology. The core is directly made into two-dimensional slices or the pore structure is replicated into two-dimensional slices of materials such as glass, and then gas-water displacement and observation are carried out. Although this method can visually observe gas-water seepage, there are obvious differences between the two-dimensional pore space and the three-dimensional pore space of the real core, and this difference is particularly obvious in karst reservoirs. The reason is that the size of the karst caves in karst reservoirs is significantly larger than the size of the pores in conventional reservoirs, resulting in the gravitational influence on the fluid in the karst caves being significantly stronger than the influence of the fluid surface tension. However, the thickness of the observation samples prepared by the two-dimensional visualization gas-water seepage measurement method is extremely small, almost completely ignoring the influence of gravity, making the observation of gas-water seepage in karst reservoirs have certain limitations. Therefore, there is an urgent need to design a three-dimensional visualization device for gas-water seepage and resistance measurement in karst reservoirs to solve the deficiencies of the existing gas-water two-phase seepage and resistivity measurement technologies in terms of visualization and the influence of fluid gravity. Summary of the Invention

[0004] The purpose of the present invention is to provide a three-dimensional visualization device and method for gas-water seepage and resistivity measurement in karst caves, which can carry out three-dimensional visualization gas-water displacement experiments, and can dynamically observe gas-water seepage characteristics and measure resistivity under the condition of considering the influence of fluid gravity, so as to obtain the three-dimensional gas-water space distribution at any water saturation state of the karst reservoir and the resistivity under the corresponding state.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] A three-dimensional visualization device for measuring gas-water seepage and resistivity in karst caves, comprising: 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;

[0007] The three-dimensional visualization measurement model is arranged on the stage;

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

[0009] The three-dimensional visualization measurement model is a transparent model printed by 3D printing technology based on the core karst cave structure. Conductive metal grid sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces are respectively arranged on the left and right sides of the three-dimensional visualization measurement model. The conductive metal grid sheets are externally connected with wires, the transparent fluid inlet and outlet channels are communicated with the transparent fluid conduit interfaces, and the transparent fluid conduit interfaces are externally connected with fluid conduits;

[0010] The constant fluid pump is communicated with one of the transparent fluid conduit interfaces through a fluid conduit and is used to inject fluid into the three-dimensional visualization measurement model;

[0011] The fluid recovery device is communicated with the other transparent fluid conduit interface through a fluid conduit and is used to collect the fluid flowing out of the three-dimensional visualization measurement model;

[0012] The resistance measurement device is electrically connected with the conductive metal grid sheets through wires 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 the fluid in the three-dimensional visualization measurement model from multiple perspectives.

[0014] Further, the left side of the three-dimensional visualization measurement model is the fluid injection side, and the constant fluid pump is communicated with 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 communicated with the transparent fluid conduit interface on the right side of the three-dimensional visualization measurement model through a fluid conduit.

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

[0017] The two video recording devices respectively record the flow and distribution of the fluid in the three-dimensional visualization measurement model from the front view and the top view directions.

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

[0019] Extract the core karst cave space: After CT scanning the cores in the study area, obtain the skeleton and karst cave structure data of the cores through image processing technology, and select representative core karst cave structures and extract them into a cubic area to obtain a core karst cave space in cubic form;

[0020] Print the transparent karst cave area: Using the core karst cave space in cubic form as a template, adopt a transparent compressive material and use 3D printing technology to print out the transparent karst cave area, and the transparent karst cave area contains the core karst cave structure;

[0021] Fabricate a conductive metal mesh sheet: Fabricate a conductive metal mesh sheet with the same lateral area as the transparent karst cave area, and extend a part of the top of the conductive metal mesh sheet as an electrode for connecting with a wire;

[0022] Print the transparent fluid inlet and outlet channels: Adopt the same transparent compressive material as the transparent karst cave area to fabricate the transparent fluid inlet and outlet channels. One side of the transparent fluid inlet and outlet channels has the same lateral area as the transparent karst cave area, and the other side has a hollow cylindrical channel with a certain length;

[0023] Print the transparent fluid conduit interface: Adopt the same transparent compressive material as the transparent karst cave area to fabricate the transparent fluid conduit interface. The transparent fluid conduit interface is a hollow cylinder, whose outer diameter is the same as the diameter of the hollow cylindrical channel of the transparent fluid inlet and outlet channels, and its inner diameter is the same as the size of the fluid conduit to ensure that the fluid conduit can be connected;

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

[0025] On the other hand, the present invention also provides a method for measuring the gas-water seepage and resistivity of a three-dimensional visualization karst cave, which is applied to the above-mentioned three-dimensional visualization gas-water seepage and resistivity measurement device for a karst cave, and includes the following steps:

[0026] Based on the core karst cave structure in the study area, adopt a transparent compressive material and print through 3D printing technology to obtain a three-dimensional visualization measurement model in a transparent state. The three-dimensional visualization measurement model includes a transparent karst cave area and the conductive metal mesh sheet, the transparent fluid inlet and outlet channels, and the transparent fluid conduit interface assembled on the left and right sides of the transparent karst cave area respectively;

[0027] Assemble the three-dimensional visualization measurement model into the three-dimensional visualization gas-water seepage and resistivity measurement device for a karst cave;

[0028] A gas-water displacement experiment is carried out using a colored salt solution. Based on the images of the salt solution distribution states in the front view and top view directions captured by a video recording device, the water saturation under this salt solution distribution state is obtained.

[0029] Through a resistance measuring device, the resistance corresponding to the three-dimensional visualization measurement model under a certain water saturation state is obtained, and the corresponding resistivity is obtained by converting through the pre-measured resistivity calibration coefficient K.

[0030] Furthermore, the method of carrying out the gas-water displacement experiment using a colored salt solution and obtaining the water saturation under this salt solution distribution state based on the images of the salt solution distribution states in the front view and top view directions captured by a video recording device specifically includes:

[0031] Calculate the core porosity through formula (1):

[0032]

[0033] In the formula, is the core porosity, %; px pore is the number of pixel points corresponding to the core cave structure obtained during the extraction of the core cave space, dimensionless; px ma is the number of pixel points of the known core skeleton, dimensionless;

[0034] Based on the images of the salt solution distribution states in the front view and top view directions captured by a video recording device, calculate the number of pixel points of the core cave structure occupied by the salt solution, and then calculate the water saturation under this salt solution distribution state through formula (2):

[0035]

[0036] In the formula, Sw is the water saturation, %; px w is the number of pixel points of the core cave structure occupied by the salt solution, dimensionless; px pore is the number of pixel points corresponding to the core cave structure, dimensionless.

[0037] Furthermore, the measurement method of the resistivity calibration coefficient K is:

[0038] Use the same transparent printing material as the three-dimensional visualization measurement model, and prepare a three-dimensional visualization calibration model through 3D printing technology. The transparent hollow area of the three-dimensional visualization calibration model is a hollow cube structure, and 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 assembled with conductive metal grid sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces that are the same as those of the three-dimensional visualization measurement model;

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

[0040] After the three-dimensional visualization calibration model is completely filled with salt solution, use a resistance measurement device to measure the resistance of the three-dimensional visualization calibration model. Given the resistivity of the salt solution, the ratio of the two is the resistivity calibration coefficient K, which is expressed by the formula:

[0041]

[0042] In the formula, K is the resistivity calibration coefficient, m; R w is the resistivity of the salt solution, Ω·m; r c is the resistance of the three-dimensional visualization calibration model measured after it is completely filled with salt solution, Ω.

[0043] Furthermore, the calculation formula for 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 is the resistivity of the three-dimensional visualization measurement model under the same water saturation, Ω·m; K is the resistivity calibration coefficient, m; r m is the resistance of the three-dimensional visualization measurement model under a certain water saturation state, Ω.

[0046] According to the specific embodiments provided by the present invention, the following technical effects are disclosed: The three-dimensional visualization gas-water seepage and resistivity measurement device and method provided by the present invention. 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. Among them, the three-dimensional visualization measurement model is a transparent model printed by 3D printing technology based on the core karst cave structure, and can be used to simulate the three-dimensional karst cave space structure of a real karst reservoir. Using this device to carry out gas-water displacement experiments, the three-dimensional gas-water spatial distribution under any water saturation state of the karst reservoir and the resistivity under the corresponding state can be obtained.

[0047] For the core of carbonate karst reservoirs, existing rock electricity experiments can easily obtain their resistivity responses, but the gas-water seepage state in the karst cave space cannot be observed. The device provided by the present invention can simultaneously observe the gas-water seepage characteristics in the karst cave 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. However, most samples are two-dimensional karst cave structures extracted from two-dimensional core photos, which are very different from real karst cave structures. Based on 3D printing technology, the present invention extracts real three-dimensional karst cave structures and prepares transparent models with the same karst cave space. By combining simulated gas-water seepage and resistivity measurement experiments and performing data conversion, the seepage characteristics and resistivity response characteristics of karst cave reservoirs can be reflected. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0050] Figure 1 It is a schematic structural diagram of a three-dimensional visualization karst cave gas-water seepage and resistivity measurement device of the present invention;

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

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

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

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

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

[0056] Figure 7Schematic diagram of the interface structure of the transparent fluid conduit in the embodiment of the present invention. Herein, 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 Schematic diagram of the three-dimensional visualization scale model in the embodiment of the present invention. Herein, 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: 1. Three-dimensional visualization measurement model; 2. Carriage; 3. Constant fluid pump; 4. Resistance measurement device; 5. Fluid recovery device; 6. Video recording device; 7. Fluid conduit; 8. Conducting wire;

[0059] 1-1. Transparent karst cave area; 1-2. Conductive metal grid sheet; 1-3. Transparent fluid inlet and outlet channel; 1-4. Transparent fluid conduit interface;

[0060] 1-1'. Transparent hollowed-out area; 1-2-1. Grid area; 1-2-2. Electrode; 1-3-1. Irregular hexahedron hollow channel; 1-3-2. Hollow cylinder. Detailed implementation manners

[0061] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0062] Aiming at the shortcomings of the existing gas-water two-phase seepage and resistivity measurement technologies in terms of visualization and the influence of fluid gravity, the present invention provides a three-dimensional visualization gas-water seepage and resistivity measurement device for karst cave reservoirs. By using this device to carry out gas-water displacement experiments, the three-dimensional gas-water spatial distribution at any water saturation state of the karst cave reservoir and the resistivity in the corresponding state can be obtained.

[0063] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

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

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

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

[0067] The three-dimensional visualization measurement model 1 is a transparent model printed by 3D printing technology based on the core karst cave structure. The transparent model includes a transparent karst cave area, and the core karst cave structure is included in the transparent karst cave area; Conductive metal mesh sheets 1-2, transparent fluid inlet / outlet channels 1-3 and transparent fluid conduit interfaces 1-4 are respectively arranged on the left and right sides of the three-dimensional visualization measurement model 1. The conductive metal mesh sheet 1-2 is externally connected to a wire 8. The transparent fluid inlet / outlet channel 1-3 is communicated with the transparent fluid conduit interface 1-4, and 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 communicated with the transparent fluid conduit interface 1-4 on the left side of the three-dimensional visualization measurement model 1 through the fluid conduit 7 for injecting fluid into the three-dimensional visualization measurement model; Exemplarily, the fluid is gas or 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 communicated with the transparent fluid conduit interface 1-4 on the right side of the three-dimensional visualization measurement model 1 through the fluid conduit 7 for collecting the fluid flowing out of the three-dimensional visualization measurement model, which can be used for recycling;

[0070] The resistance measurement device 4 is electrically connected to the conductive metal mesh sheet 1-2 through the wire 8 for measuring 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 the fluid in the three-dimensional visualization measurement model 1 from multiple perspectives (for example, two directions of front view and top view);

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

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

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

[0075] Specifically, as Figure 2 shown, the preparation method of the three-dimensional visualization measurement model 1 includes the following six steps:

[0076] ① Core karst cave space extraction:

[0077] After CT scanning the core in the study area, the skeleton and karst cave structure data of the core are obtained through image processing technology; then, a representative karst cave structure area is selected and extracted into a cubic area to obtain the core karst cave space in cubic form.

[0078] ② Transparent karst cave area printing:

[0079] Using the core karst cave space in cubic form as a template, a transparent compressive material is used, and 3D printing technology is used to print out the transparent karst cave area 1-1;

[0080] ③ Conductive metal grid sheet production:

[0081] A metal material with strong conductivity (such as gold, copper, aluminum alloy, etc.) is selected and processed into a conductive metal grid sheet 1-2 with the same lateral area as the transparent karst cave area and a relatively thin thickness. It is required that the grid density inside the conductive metal grid sheet 1-2 is appropriate, that is, the conductive metal grid sheet 1-2 must be in contact with the fluid, but will not completely block the inflow and outflow of the fluid. It is also required that a part of the top of the conductive metal grid sheet 1-2 extends as an electrode for connecting with the wire 8;

[0082] ④ Transparent fluid inlet and outlet channel printing:

[0083] Using the same transparent compressive material as the transparent karst cave area, a transparent fluid inlet and outlet channel 1-3 is made. One side of the transparent fluid inlet and outlet channel 1-3 has the same lateral area as the transparent karst cave area, and the other side has a hollow cylindrical channel with a certain length;

[0084] ⑤ Transparent fluid conduit interface printing:

[0085] Using the same transparent compressive material as the transparent karst cave area, a transparent fluid conduit interface 1-4 is made. The transparent fluid conduit interface 1-4 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, ensuring that the fluid conduit 7 can be connected;

[0086] ⑥ Three-dimensional visualization measurement model assembly:

[0087] Using techniques such as thermocompression bonding, micro-encapsulation bonding, or precision adhesion, assemble the above-mentioned parts, namely the transparent karst cave area 1-1, the conductive metal mesh sheet 1-2, the transparent fluid inlet / outlet channel 1-3, and the transparent fluid conduit interface 1-4 together. It is required that the contact areas between the parts are completely sealed and remain transparent, and finally a three-dimensional visualization measurement model is obtained, as shown in Figure 2 shown as A in

[0088] On the other hand, the present invention also provides a method for measuring gas-water seepage and resistivity in a three-dimensional visualization karst cave, which is applied to the above-mentioned three-dimensional visualization gas-water seepage and resistivity measurement device in a karst cave, and includes the following steps:

[0089] S1, based on the core karst cave structure in the study area, use a transparent compressive material and print a three-dimensional visualization measurement model in a transparent state through 3D printing technology. The three-dimensional visualization measurement model includes a transparent karst cave area and conductive metal mesh sheets, transparent fluid inlet / outlet channels, and transparent fluid conduit interfaces assembled on the left and right sides of the transparent karst cave area respectively;

[0090] The specific preparation method of the three-dimensional visualization measurement model is the 6 steps of the preparation method of the three-dimensional visualization measurement model as described above;

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

[0092] S3, conduct a gas-water displacement experiment using a colored salt solution, and obtain the water saturation under the distribution state of the salt solution based on the images of the salt solution distribution state taken by the video recording device in the front view direction and the top view direction; specifically, the calculation of porosity and water saturation is as follows:

[0093] During the extraction process of the core karst cave space, the number of pixel points (px pore ) corresponding to the real karst cave space structure of the core can be obtained, and the number of pixel points (px ma ) corresponding to the core skeleton is known. The core porosity can be calculated through formula (1):

[0094]

[0095] In the formula, is the core porosity, %; px pore is the number of pixel points of the karst cave, dimensionless; px ma is the number of pixel points of the core skeleton, dimensionless.

[0096] Select a salt solution with a special color for the gas-water displacement experiment, and the distribution state of the salt solution in the cavern space of the three-dimensional visualization measurement model can be easily observed. Based on the images of the salt solution distribution state in the front view and top view directions taken by the video recording device, the number of pixel points (px w ) occupied by the salt solution in the cavern space can be calculated, and then the water saturation (Sw) under this salt solution distribution state can be calculated through formula (2):

[0097]

[0098] In the formula, Sw is the water saturation, %; px w is the number of pixel points of the salt solution, dimensionless; px pore is the number of pixel points of the core cavern, dimensionless.

[0099] S4. Through the resistance measurement device, obtain the resistance corresponding to the three-dimensional visualization measurement model under a certain water saturation state, and convert it to the corresponding resistivity through the previously measured resistivity calibration coefficient K.

[0100] Among them, the measurement method of the resistivity calibration coefficient K is as follows:[[]]

[0101] As Figure 3 shown, use the same transparent printing material as the three-dimensional visualization measurement model, and prepare a three-dimensional visualization calibration model through 3D printing technology. The transparent hollow area 1-1' of the three-dimensional visualization calibration model is a hollow cube structure, as Figure 4 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 cavern 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 grid sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces as the three-dimensional visualization measurement model;

[0102] Replace the three-dimensional visualization calibration model with the three-dimensional visualization measurement model and assemble it into the three-dimensional visualization cavern gas-water seepage and resistivity measurement device;

[0103] After the three-dimensional visualization calibration model is completely filled with salt solution, use the resistance measurement device to measure the resistance of the three-dimensional visualization calibration model, and knowing the resistivity of the salt solution, the ratio of the two is the resistivity calibration coefficient K, which is expressed by the formula as:[[]]

[0104]

[0105] In the formula, K is the resistivity calibration coefficient, m; R w is the resistivity of the salt solution, Ω·m; r c is the resistance of the three-dimensional visualization calibration model measured after being completely filled with salt solution, Ω.

[0106] Using a resistance measurement device, obtain the resistance r of the three-dimensional visualization measurement model corresponding to a certain water saturation state. m ; Then, using formula (4), obtain the resistivity R of the three-dimensional visualization measurement model corresponding to this water saturation state. m ; The resistivity (R m ) of the three-dimensional visualization measurement model can be approximately equal to the true resistivity (R t ) of the core. The calculation formula for 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 is the resistivity of the three-dimensional visualization measurement model under the same water saturation, in Ω·m; K is the resistivity calibration coefficient, in m; r m is the resistance of the three-dimensional visualization measurement model under a certain water saturation state, in Ω.

[0109] Among them, the meaning of the three-dimensional visualization calibration model:

[0110] The original experimental data measured by the three-dimensional visualization measurement model is resistance, and the resistivity needs to be obtained through conversion by the resistivity calibration coefficient K. The resistivity calibration coefficient K is related to the structure of the three-dimensional visualization measurement model and can be obtained through the three-dimensional visualization calibration model. For a three-dimensional visualization measurement model with a fixed size, only one three-dimensional visualization calibration model of the same size needs to be made. Under the condition of ensuring that the external conditions remain unchanged, the resistivity calibration coefficient K of the same three-dimensional visualization measurement model is constant. Therefore, only the resistivity (R w ) of the salt solution and the resistance (r c ) of the calibration model completely filled with the salt solution need to be measured once in the whole experiment. This avoids the cumbersome measurement of the resistivity of the salt solution and the three-dimensional visualization calibration model.

[0111] The structure and preparation of the three-dimensional visualization calibration model:

[0112] As Figure 3 shown, use the same transparent printing material as the transparent karst cave area to prepare the three-dimensional visualization calibration model. The difference between the three-dimensional visualization measurement model and the three-dimensional visualization calibration model sample is that the transparent hollow area of the three-dimensional visualization calibration model sample is a hollow cube structure, its external dimensions are the same as those of the three-dimensional visualization measurement model, the internal dimensions are the largest inscribed cube of the karst cave space in the three-dimensional visualization measurement model, and the rest of the parts are exactly the same; and the parts are combined according to the same combination technology and requirements as the three-dimensional visualization measurement model, and finally the three-dimensional visualization calibration model is obtained.

[0113] Embodiment

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

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

[0116] The preparation of the three-dimensional visualization measurement model is completed according to the aforementioned 6 steps.

[0117] ① Extraction of core karst cave space

[0118] Select the core of a karst cave type carbonate rock reservoir in a certain area. After CT scanning, intercept a core data area with a length of 4 cm, a width of 4 cm, and a height of 4 cm. Through image processing technology, obtain the skeleton and karst cave structure data of the core. After segmenting the representative karst cave structure, extract it to the center of a cube area with a length of 4 cm, a width of 6 cm, and a height of 6 cm to obtain a karst cave space in the form of a cube.

[0119] ② Printing of transparent karst cave area

[0120] Using the above cube karst cave space as a template, adopt a transparent compressive material and use 3D printing technology to print a transparent karst cave area with a length of 4 cm, a width of 6 cm, and a height of 6 cm, such as Figure 4 part 1-1 in the figure.

[0121] ③ Fabrication of conductive metal grid sheet

[0122] As shown in Figure 5 , select metal copper as the material for the conductive metal. First, fabricate a conductive metal sheet with a length of 6 cm, a height of 8 cm, and a thickness of 0.05 cm. Then, cut and process the conductive metal sheet. First, leave 3 cm extending inward from the upper edge, and leave 1 cm extending inward for the remaining three edges. The single grid strip cut is 4 cm in length, 0.2 cm in width, and 0.05 cm in thickness. The overall area is a grid area with a length of 4 cm, a width of 4 cm, and a thickness of 0.05 cm (such as Figure 5 , part 1-2-1), and make the grid able to contact the fluid but not completely block the inflow and outflow of the fluid; cut out a part with a length of 1 cm, a height of 2 cm, and a thickness of 0.05 cm from the center of the upper edge of the metal sheet as the electrode ( Figure 5 , part 1-2-2) to obtain the final conductive metal grid sheet ( Figure 5 , part 1-2).

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

[0124] As shown in Figure 6As shown in the figure, a transparent fluid inlet and outlet channel 1-3 is made of the same transparent compressive material as the transparent karst cave area. The overall dimensions of the transparent fluid inlet and outlet channel 1-3 are 2 cm in length, 6 cm in width, and 6 cm in height. On one side inside, there is an irregular hexahedron hollow channel 1-3-1 with a central circle of 1 cm in diameter and a central rectangle of 4 cm in length and 4 cm in width as the upper and lower bases, and a height of 1.5 cm. At the same time, on the other side inside, there is a hollow cylindrical channel with a certain length, in the shape of a hollow cylinder 1-3-2 with a diameter of 1 cm and a length of 0.5 cm.

[0125] ⑤ Printing of transparent fluid conduit interface

[0126] As Figure 7 shown in the figure, a transparent fluid conduit interface 1-4 is made of the same transparent compressive material as the transparent karst cave area. The transparent fluid conduit interface 1-4 is a hollow cylinder with an outer diameter of 1 cm, an inner diameter of 0.6 cm, and a length of 2 cm.

[0127] ⑥ Assembly of three-dimensional visualization measurement model

[0128] Using high-temperature bonding technology, assemble the above parts in the order shown in B in Figure 2 from left to right, ensuring that the contact areas between the parts are completely sealed; the connectivity of all printed channels and regions is unobstructed and remains transparent, and finally obtain a three-dimensional visualization measurement model.

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

[0130] As Figure 8 shown in the figure, a three-dimensional visualization scale model is made of the same transparent compressive material as the transparent karst cave area. The difference between the three-dimensional visualization measurement model and the three-dimensional visualization scale model is that the transparent hollow area 1-1' of the three-dimensional visualization scale model is a hollow cube structure, with an external cube size of 4 cm in length, 6 cm in width, and 6 cm in height, and an internal hollow cube size of 4 cm in length, 4 cm in width, and 4 cm in height. The rest of the parts are exactly the same; and using the same bonding technology and requirements as the three-dimensional visualization measurement model, assemble the parts in the order shown in B in Figure 3 to assemble each part, and finally obtain a three-dimensional visualization scale model.

[0131] (3) Structure of the assembled total device

[0132] According to Figure 1The overall device for simulating gas-water seepage and resistivity measurement in a karst reservoir is set up as follows. Fix the stage 2 horizontally, and fix the three-dimensional visualization measurement model 1 at the center of the stage 2. Connect the constant fluid pump 3 to the fluid conduit 7 externally, and then connect it to the fluid conduit interface in the fluid inlet area of the three-dimensional visualization measurement model 1. The fluid recovery device 5 is also connected to the fluid conduit externally and then connected to the fluid conduit interface in the fluid outlet area of the three-dimensional visualization measurement model. One end of the wire 8 is connected to the resistance measurement device 4, and the other end of the wire 8 is clamped on the electrode of the conductive metal grid sheet in the three-dimensional visualization measurement model 1. Install the video recording devices 6 respectively directly above and in front of the three-dimensional visualization measurement model 1, so that the karst cave area of the three-dimensional visualization measurement model is completely at the center of the video recording field of view and the captured images are clear and non-overlapping. Among them, during the experiment of the three-dimensional visualization measurement model, in order to determine the resistivity scale factor K, it can be replaced by the three-dimensional visualization scale model, and its connection method is the same as that of the three-dimensional visualization measurement model.

[0133] (4) Measurement data processing

[0134] ① Porosity and water saturation calculation

[0135] During the extraction process of the core karst cave space, the number of pixel points (px pore = 28590396) corresponding to the real karst cave space structure of the core can be obtained, and the number of pixel points (px ma = 775766604) corresponding to the core skeleton is known. Through formula (5), the core porosity ( rounded to three decimal places) can be calculated:

[0136]

[0137] In the formula, is the core porosity, %; px pore is the number of pixel points of the karst cave, dimensionless; px ma is the number of pixel points of the core skeleton, dimensionless.

[0138] A salt solution with a special color is selected for the gas-water displacement experiment, so it is easy to observe the distribution state of the salt solution in the karst cave space in the three-dimensional visualization measurement model. Based on the images of the salt solution distribution state in the front view and top view directions captured by the video recording device, the number of pixel points (px w = 16060860) of the karst cave space occupied by the salt solution can be calculated, and then the water saturation (Sw rounded to three decimal places) under this salt solution distribution state can be calculated through formula (6):

[0139]

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

[0141] ②Determination of resistivity calibration coefficient K

[0142] After the three-dimensional visualization scale model is completely filled with salt solution, the resistance of the three-dimensional visualization scale model (r c =2.304Ω); and the resistivity of the salt solution (R w =0.053Ω.m), the ratio of the two is the resistivity scale factor K, which is expressed by formula (7):

[0143]

[0144] Where K is the resistivity scale factor, m; R w is the resistivity of the salt solution, Ω.m; r c The resistance of the 3D visualization scale model after it is completely filled with salt solution, in Ω.

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

[0146] The resistance (r) corresponding to the three-dimensional visual measurement model under the water saturation state obtained by formula (6) is obtained through the resistance measurement device. m =581.164Ω); then using formula (8), the resistivity (R m Keep three decimal places); 3D visualization of the resistivity of the measurement model (R m ) can be approximately equal to the true resistivity of the core (R t ).

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

[0148] Where R m is the resistivity of the three-dimensional visualization measurement model under the same water saturation, Ω.m; K is the resistivity scale factor, m; r m is the resistance of the 3D visual measurement model under a certain water saturation state, Ω.

[0149] In this article, specific examples are used to elaborate on the principles and implementation modes of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation modes and application scopes. To sum up, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A three-dimensional visualization device for measuring gas-water seepage and resistivity in karst caves, characterized in that, Comprising: 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 arranged on the stage; The stage is used to fix the three-dimensional visualization measurement model to prevent the three-dimensional visualization measurement model from shifting; The three-dimensional visualization measurement model is a transparent model printed by 3D printing technology based on the core karst structure. Conductive metal mesh sheets, transparent fluid inlet and outlet channels, and transparent fluid conduit interfaces are respectively arranged on the left and right sides of the three-dimensional visualization measurement model. The conductive metal mesh sheets are externally connected with wires, the transparent fluid inlet and outlet channels are communicated with the transparent fluid conduit interfaces, and the transparent fluid conduit interfaces are externally connected with fluid conduits; The constant fluid pump is communicated with one of the transparent fluid conduit interfaces through a fluid conduit and is used to inject fluid into the three-dimensional visualization measurement model; The fluid recovery device is communicated with the other transparent fluid conduit interface through a fluid conduit and is used to collect the fluid flowing out of the three-dimensional visualization measurement model; The resistance measurement device is electrically connected with the conductive metal mesh sheet 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 the fluid in the three-dimensional visualization measurement model from multiple perspectives.

2. The three-dimensional visualization karst cave air-water seepage and resistivity measurement device 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 communicated with 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 communicated with the transparent fluid conduit interface on the right side of the three-dimensional visualization measurement model through a fluid conduit.

3. The three-dimensional visualization device for measuring gas-water seepage and resistivity in karst caves according to claim 1, wherein The video recording device is respectively arranged directly above and in front of the three-dimensional visualization measurement model, so that the karst structure area of the three-dimensional visualization measurement model is completely in the center of the video field of view and the captured images are clear and non-overlapping; The two video recording devices respectively record the flow and distribution of the fluid in the three-dimensional visualization measurement model from the front view and the top view.

4. The three-dimensional visualization karst cave air-water seepage and resistivity measurement device according to claim 1, characterized in that The preparation method of the three-dimensional visualization measurement model includes the following steps: Extracting the core karst space: After CT scanning the cores in the study area, obtaining the core skeleton and karst structure data through image processing technology, and selecting a representative core karst structure and extracting it into a cubic region to obtain a cubic-shaped core karst space; Printing the transparent karst area: Using the cubic-shaped core karst space as a template, adopting a transparent compressive material, and using 3D printing technology to print out the transparent karst area, and the transparent karst area contains the core karst structure; Making the conductive metal mesh sheet: Making a conductive metal mesh sheet with the same lateral area as the transparent karst area, and extending a part of the top of the conductive metal mesh sheet as an electrode for connecting with a wire; Printing the transparent fluid inlet and outlet channels: Using the same transparent compressive material as the transparent karst area to make the transparent fluid inlet and outlet channels. One side of the transparent fluid inlet and outlet channels has the same lateral area as the transparent karst area, and the other side has a hollow cylindrical channel with a certain length; Printing a transparent fluid conduit interface: A transparent fluid conduit interface is fabricated using the same transparent compressive material as that of the transparent karst cave area. The transparent fluid conduit interface is a hollow cylinder with an outer diameter equal to that of the hollow cylindrical channel of the transparent fluid inlet / outlet channel and an inner diameter equal to that of the fluid conduit, ensuring that the fluid conduit can be connected. Assembling a three-dimensional visualization measurement model: Conductive metal mesh sheets, transparent fluid inlet / outlet channels, and transparent fluid conduit interfaces are respectively assembled on the left and right sides of the transparent karst cave area to obtain a completely sealed and transparent three-dimensional visualization measurement model.

5. A three-dimensional visualization method for gas-water seepage and resistivity measurement in karst caves, which is applied to the three-dimensional visualization device for gas-water seepage and resistivity measurement in karst caves according to any one of claims 1-4, characterized in that, Including the following steps: Based on the core karst cave structure of the study area, a three-dimensional visualization measurement model in a transparent state is printed using a transparent compressive material through 3D printing technology. The three-dimensional visualization measurement model includes a transparent karst cave area and conductive metal mesh sheets, transparent fluid inlet / outlet channels, and transparent fluid conduit interfaces respectively assembled on the left and right sides of the transparent karst cave area. Assembling the three-dimensional visualization measurement model into a three-dimensional visualization karst cave air-water seepage and resistivity measurement device. Conducting an air-water displacement experiment using a colored salt solution, and obtaining the water saturation under the distribution state of the salt solution based on the images of the salt solution distribution state in the front view and top view directions captured by a video recording device. Through a resistance measurement device, obtaining the resistance corresponding to the three-dimensional visualization measurement model under a certain water saturation state, and converting it to the corresponding resistivity through the pre-measured resistivity scale coefficient K.

6. The three-dimensional visualization method for measuring gas-water seepage and resistivity in karst caves according to claim 5, characterized in that The step of conducting an air-water displacement experiment using a colored salt solution and obtaining the water saturation under the distribution state of the salt solution based on the images of the salt solution distribution state in the front view and top view directions captured by a video recording device specifically includes: Calculating the core porosity through formula (1): In the formula, is the core porosity, %; px pore is the number of pixel points corresponding to the core karst structure obtained during the extraction of the core karst space, dimensionless; px ma is the number of pixel points of the known core skeleton, dimensionless; Based on the images of the salt solution distribution state in the front view and top view directions captured by a video recording device, calculating the number of pixel points of the core karst cave structure occupied by the salt solution, and then calculating the water saturation under the distribution state of the salt solution through formula (2): where Sw is the water saturation, %; px w is the number of pixel points of the core karst structure occupied by the salt solution, dimensionless; px pore is the number of pixel points corresponding to the core karst structure, dimensionless.

7. The three-dimensional visualization method for gas-water seepage and resistivity measurement in karst caves according to claim 5, characterized in that, The measurement method of the resistivity scale coefficient K is as follows: Using the same transparent printing material as the three-dimensional visualization measurement model, a three-dimensional visualization scale model is prepared through 3D printing technology. The transparent hollow area of the three-dimensional visualization scale model is a hollow cube structure with an external size equal to that of the three-dimensional visualization measurement model. The hollow cube structure is the largest inscribed cube of the transparent karst cave area of the three-dimensional visualization measurement model. Conductive metal mesh sheets, transparent fluid inlet / outlet channels, and transparent fluid conduit interfaces identical to those of the three-dimensional visualization measurement model are assembled on the left and right sides of the hollow cube structure. Replacing the three-dimensional visualization measurement model with the three-dimensional visualization scale model and assembling it into a three-dimensional visualization karst cave air-water seepage and resistivity measurement device. After filling the three-dimensional visualization scale model completely with the salt solution, measuring the resistance of the three-dimensional visualization scale model using a resistance measurement device, and knowing the resistivity of the salt solution, the ratio of the two is the resistivity scale coefficient K, which is expressed by the formula: In the formula, K is the resistivity scale coefficient, m; R w is the resistivity of the salt solution, Ω·m; r c is the resistance of the three-dimensional visualization scale model measured after it is completely filled with the salt solution, Ω.

8. The three-dimensional visualization method for gas-water seepage and resistivity measurement in karst caves according to claim 7, characterized in that, The calculation formula for the resistivity of the three-dimensional visualization measurement model is as follows: R m = K × r m (4) where R m is the resistivity of the three-dimensional visualization measurement model at the same water saturation, Ω·m; K is the resistivity scale factor, m; r m The resistance of the three-dimensional visualization measurement model at a certain water saturation state, Ω.

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