Simulation fracture multiphase flow visualization test system and method of variable structure in flowing water environment

Abstract

The invention discloses a simulation fracture multiphase flow visualization test system of a variable structure in a dynamic water environment. The simulation fracture multiphase flow visualization test system comprises a simulation fracture model, a hydrodynamic force control module, a visualization observation module and a supporting structure. The simulation fracture model is composed of a transparent fracture structure and an external clamp, the transparent fracture is prepared by rolling over rock samples which are obtained through splitting or 3D printing and have different roughness and sizes, and the fracture opening degree and the filling degree are flexibly adjusted and controlled by adjusting the thickness of a gasket and the volume of filler. And the visualization module consists of a camera and a light source which are arranged above and below the crack model and is used for recording the multiphase flow process. The hydrodynamic control module is composed of a Markov bottle, a flow meter, an injection pump and a pressure sensor and is connected with the fracture model through a hose, and accurate control over the dynamic water environment and the second-phase liquid injection condition is achieved. The device has the characteristics of being variable in fracture rough structure and size, controllable in hydrodynamic condition, visualized in flowing process and the like, and provides important support for researching the fracture multiphase flowing law.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock mass seepage and multiphase flow research. Specifically, it relates to a visual rock fracture multiphase flow test system under a dynamic water environment, and also relates to a method for conducting tests using this system. Background Technique

[0002] Under the influence of long-term geological actions and engineering activities, rock masses often develop a large number of joints, fractures and other preferential flow channels. And affected by lithological differences and types of geological actions, fracture structures show different characteristics such as wall roughness, aperture, length, width, etc. Their interiors are also often partially or completely filled with particulate matter such as clay, sand grains, debris and proppants. In engineering practices such as the grouting and plugging of water inrush from surrounding rocks, the hydraulic fracturing exploitation of oil and gas, and the storage of underground water-sealed oil depots, the multiphase flow law in filled fractures under a dynamic water environment is often the key scientific issue of concern. At present, the experimental research on filled fractures is usually a black-box test based on a real rock model, and the flow process of fluids and particulate matters in filled fractures cannot be directly observed. Therefore, carrying out visual experimental research on multiphase flow in filled fractures under a dynamic water environment has great engineering value and theoretical significance.

[0003] Visualization research based on optical principles is an important means to reveal the multiphase flow law of fluids and particles in fractures in the laboratory at present. However, how to prepare transparent simulation fracture models with different rough structural characteristics, variable sizes and fillability, and how to achieve the matching simulation and precise control of the dynamic water environment are still technical problems to be solved. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a variable-structure simulation fracture multiphase flow visualization test system and method under a dynamic water environment, providing technical support for further studying the multiphase flow mechanism of fluids and particles in fractures under a dynamic water environment.

[0005] The purpose of the present invention is achieved in the following way: A variable-structure simulation fracture multiphase flow visualization test system under dynamic water environment, comprising a hydrodynamic control module, a transparent simulated filled fracture model, a visualization observation module and a rod frame support structure; the hydrodynamic control module is connected to the transparent simulated filled fracture model, the transparent simulated filled fracture model is arranged on the bottom plate of the rod frame support structure, the visualization observation module is installed on the top of the rod frame support structure, and the visualization observation module is connected to the main controller; the hydrodynamic control module is installed on a liftable support platform, the hydrodynamic control module includes a Mariotte bottle installed on the top of the liftable support platform and a flowmeter installed on the bottom of the liftable support platform, the Mariotte bottle is connected to the first liquid inlet of the transparent simulated filled fracture model through a first hose, the flowmeter is installed on the first hose, and a flow rate adjustment knob is provided on the flowmeter for monitoring and further regulating the dynamic water flow rate. A first pressure sensor is installed on the first hose between the flowmeter and the simulated fracture model for monitoring the dynamic water pressure; the hydrodynamic control module further includes an injection pump, which consists of a syringe and a stepper motor. The syringe is pushed by the stepper motor to achieve a constant injection flow rate condition, and the flow rate is adjusted by changing the propulsion speed of the stepper motor and the type of syringe. The liquid outlet of the syringe is connected to the second liquid inlet of the fracture model; a second pressure sensor is arranged between the liquid outlet of the syringe and the second liquid inlet of the fracture model for monitoring the injection pressure of the second-phase liquid. The flowmeter, the first pressure sensor, the stepper motor and the second pressure sensor are all connected to the main controller, realizing the regulation and control of the dynamic water pressure, the dynamic water flow rate and the injection flow rate of the second-phase liquid.

[0006] For the above variable-structure simulation fracture multiphase flow visualization test system under dynamic water environment, the simulated filled fracture model includes a transparent simulated fracture structure, granular fillings, two side baffles, a liquid inlet groove, a liquid outlet groove, an external model fixture and a waste liquid collection tank; the liquid inlet and outlet of the transparent simulated fracture structure are respectively butted with the liquid inlet groove and the liquid outlet groove, and its two sides are respectively butted with the two side baffles. Waterproof rubber strips are pasted on the contact surfaces of the liquid inlet groove, the liquid outlet groove, the two side baffles and the fracture structure, and they are placed together in the center of the external model fixture and fixed and sealed by means of screw extrusion.

[0007] The above-mentioned simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment, the transparent simulation fracture structure includes an upper plate and a lower plate of the transparent simulation fracture, which are made by casting a fracture specimen with different rough structures and sizes, and using transparent epoxy resin or glass material; after casting, the two long sides of the upper and lower plates of the fracture are polished to form two gasket platforms; a second liquid inlet is provided at the middle position of the fracture model, which is connected to the liquid outlet of the syringe through a third hose; high-strength metal gaskets are placed on the gasket platforms of the lower plate of the fracture, the length of which is equal to the length of the fracture structure, and the width is equal to the width of the gasket platform. Different gasket thicknesses are used to adjust the aperture and the size of the internal cavity of the fracture structure; the granular filling material is placed on the surface of the lower plate of the fracture, and the filling degree is controlled by changing the ratio of the apparent volume of the filling material to the cavity volume. Subsequently, the upper and lower plates of the fracture are assembled to form a transparent simulation fracture structure.

[0008] The above-mentioned simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment, the granular filling material selects different types and materials according to the test purpose; when the test research focuses on the fluid flow law in the filled fracture, the granular filling material selects gas-phase silica powder and transparent quartz sand with refractive index matching the fluid; when the test research focuses on the erosion and loss of particulate matter in the filled fracture, the granular filling material selects PE microspheres, silicon powder, and colored transparent model sand, and the fluid corresponds to colorless, and the degree of particulate matter loss is judged by observing the change of light intensity in the fracture model based on the optical principle.

[0009] The above-mentioned simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment, the liquid inlet tank and the liquid outlet tank have the same structure, the width of which is equal to the width of the fracture structure, and the thickness is equal to the thickness of the assembled fracture structure; one side of the liquid inlet and outlet tanks in contact with the fracture structure is an open space structure, and the size is larger than the effective flow-through surface of the fracture structure; a first liquid inlet is provided on the other side of the liquid inlet tank that is not in contact with the fracture structure, which is connected to the flow meter through a first hose; similarly, a liquid outlet is provided on the other side of the liquid outlet tank that is not in contact with the fracture structure, and the test fluid and the granular filling material are discharged into the waste liquid collection tank through a second hose; the two side baffles have the same structure, the length of which is equal to the length of the fracture structure, the width is 1 cm, and the height is equal to the thickness of the assembled fracture structure, and it is mainly used to squeeze and stop water on the side.

[0010] The above-mentioned simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment, the external fixture of the model includes an upper fixture, a middle frame and a lower fixture; the upper fixture and the lower fixture are symmetric in structure, and are composed of an embedded transparent square glass plate and a metal square ring, and the size of the transparent square glass plate is larger than the size of the transparent simulation fracture structure, so as to ensure the effective observation of the flow process; a group of vertical threaded through holes are provided around the metal square ring of the upper fixture, and corresponding vertical threaded holes are provided at the same positions on the metal square ring of the lower fixture. The transparent simulation fracture structure in the middle is locked with the upper and lower fixtures through vertical long screws to ensure that the opening of the fracture structure remains unchanged; an adjustable-height middle frame support plate is provided outside the lower fixture to support the middle frame and ensure that its horizontal center is consistent with the horizontal center of the transparent simulation fracture structure; a group of horizontal threaded holes are provided on the middle frame, and the side baffles, the liquid inlet tank and the liquid outlet tank are respectively fixed around the transparent simulation fracture structure through horizontal long screws; to avoid mutual interference, the positions of the horizontal threaded through holes are staggered with the positions of the vertical threaded holes in the upper and lower fixtures.

[0011] The above-mentioned simulation filled fracture multiphase flow visualization test system under dynamic water environment, the visualization observation module includes a high-speed camera, a diffuser plate, a light source and a main controller; the high-speed camera is placed above the simulation filled fracture model and fixed by the camera fixture in the rod support structure; the diffuser plate and the light source are arranged in sequence below the fracture model, and the two are adhesively connected by four plastic short columns and are placed on the support bottom plate of the rod support structure as a whole; a round hole is opened in the center of the diffuser plate, and the third hose connected to the second liquid inlet passes through the round hole and the middle part of the light source and the diffuser plate and is connected to the syringe, so as to realize the hiding of the third hose in the camera photo, which is convenient for the accurate observation, processing and analysis of the fluid flow process; the high-speed camera, the fracture model, the diffuser plate and the light source are arranged collinearly centered in the vertical direction, and the high-speed camera is connected to the main controller.

[0012] The above-mentioned simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment, the rod support structure includes a support bottom plate, a fracture model stage, two camera support vertical rods, four stage support vertical rods, and a three-dimensional adjustable camera fixture; the camera support vertical rods and the stage support vertical rods are respectively threadedly connected and fixed to the support bottom plate, and then are respectively connected to the camera fixture and the fracture model stage; a square hole is opened at the center of the fracture model stage, and the size of the square hole is larger than the size of the transparent square glass plate embedded in the lower fixture of the fracture model and smaller than the size of the metal square ring in the lower fixture of the fracture model, so as to place the fracture model and enable the lower light source to pass through the square hole and enter the fracture model.

[0013] The above-mentioned simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment. The three-dimensional adjustable camera fixture includes a slidable rod clamp, a circular connecting rod, a lateral displacement slide, a vertical displacement slide, and a camera clamping slide. The slidable rod clamp is sleeved on the support vertical rod and has a circular rod hole in the middle. One side of the circular connecting rod is connected to the back of the lateral displacement slide and fixed by a screw on the circular rod hole. The lateral displacement slide, vertical displacement slide, and camera clamping slide are respectively composed of a slide rail, a sliding block, and a sliding adjustment screw on the structure. The sliding block is adjusted to move by the sliding adjustment screw. The sliding block on the front of the lateral displacement slide is connected to the back of the vertical displacement slide, and the sliding block on the front of the vertical displacement slide is connected to the back of the camera clamping slide. The slider of the camera clamping slide is composed of two left and right side plates, and the camera is fixed by a clamping method. The lateral displacement slide, vertical displacement slide, and camera clamping slide are arranged in a cross shape in space. The camera is fixed at an appropriate height through the slidable rod clamp, and the sliding adjustment screws on the circular connecting rod, lateral, and vertical displacement slides are used to achieve rapid adjustment of the camera in three-dimensional space, so as to facilitate the adjustment of the camera's field of view, image focusing, and achieve vertical central collinearity with the fracture model and light source.

[0014] For the above-mentioned simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment, the fracture specimens with different rough structures and sizes can be prepared by one of the following two methods: 1) Method 1: Select the rock type according to the research needs, cut the collected rock according to the set size, and then use the Brazilian splitting method to prepare rock fracture specimens with different rough structures and sizes. The roughness of the obtained fracture wall surface is mainly related to the coarse particle composition inside the rock. Generally, the order of the wall surface roughness is: granite > marble > sandstone > shale; 2) Method 2: Conduct morphological statistics on the sample to be measured (the split rock structure), extract its characteristic parameters (average protrusion height, height variation coefficient, etc.), and then based on the fracture structure surface power spectrum function and random seed method proposed by Brown, write the random generation code for the simulation fracture morphology, and control the wall surface roughness by adjusting the Hurst index (usually Hurst index H = 0.7 - 0.9) in the power spectrum function through analog statistical analysis. Then, combined with 3D printing technology, obtain rock fracture printed specimens with different rough structures and sizes.

[0015] The method of conducting tests with the above-mentioned simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment includes the following steps: S1. Install the liftable support platform and rod frame support structure: Connect the support bottom plate and the support vertical rod together through a threaded structure, adjust the level of the support bottom plate and the verticality of the support vertical rod, and then connect the slidable rod clamp, the Mariotte bottle support structure, the fracture model carrier, and the camera fixture. S2. Install the transparent simulated filled fracture model: Make the upper and lower plates of the transparent simulated fracture structure by mold turning. Select the appropriate filling material type, volume, and the thickness of the metal gasket according to the test purpose and working conditions. Then assemble the simulated fracture structure and place it on the lower fixture. Adjust the height of the middle frame according to the thickness of the assembled fracture structure, and fix the liquid inlet tank, liquid outlet tank, and two side baffles to the fracture model through the horizontal screws of the middle frame. Then install the upper fixture, tighten the screws, fix the fracture structure completely at the center of the fixture, and test the airtightness of the model. Place the assembled transparent simulated filled fracture model on the stage. S3. Install the visualization observation module: Fix the high-speed camera through the camera fixture and adjust it to an appropriate height. Paste the support short columns between the diffuser plate and the light source, and place the whole on the support bottom plate. Adjust the positions of the camera, transparent simulated filled fracture model, diffuser plate, and light source so that they are collinear at the center in the vertical direction. S4. Install the hydrodynamic control module: Install the Mariotte bottle, injection pump, flowmeter, first pressure sensor, and second pressure sensor. Connect the first hose, second hose, and third hose respectively, and check the airtightness of the whole flow channel. The flowmeter, first pressure sensor, stepper motor, second pressure sensor, and high-speed camera are all connected to the main controller, realizing the regulation and control of the dynamic water pressure, dynamic water flow, and the injection flow of the second-phase liquid. S5. Set the initial test conditions and start the test: According to the test working conditions, set the height of the Mariotte bottle, the knob of the flowmeter, the injection flow of the injection pump, the frame rate of the high-speed camera, and the intensity of the light source. Turn on the first pressure sensor and the second pressure sensor, open the Mariotte bottle until the model is saturated by the dynamic water, and then turn on the high-speed camera to take pictures and open the injection pump. S6. End of the test: Close the Mariotte bottle and the flow pipeline, remove the fracture model, and then disassemble the fracture model, and clean and dry it. According to the test working conditions, repeat steps S2 and S5 to carry out the next group of tests.

[0016] Compared with the prior art, the present invention has the following technical effects: The present invention provides a visualization test system for multiphase flow in a simulated filled fracture under a dynamic water environment. The system realizes the preparation of fracture models with different rough structures, filling degrees, and sizes, the visualization observation of the multiphase flow process, and the precise control of hydrodynamic conditions, and the whole adopts a modular design. Based on this device, a visualization test of multiphase flow in a filled fracture under a dynamic water environment can be carried out. The device has strong expandability and simple operation, providing important support for studying the multiphase flow law in fractured media. Description of the Drawings

[0017] Figure 1 is the overall schematic diagram of the present invention; Figure 2It is a schematic diagram of the liftable support platform and flowmeter of the present invention; Figure 3 It is a schematic cross-sectional view of the simulated filled fracture model of the present invention along the length direction; Figure 4 It is a schematic cross-sectional view of the simulated filled fracture model of the present invention along the width direction; Figure 5 It is a schematic diagram of the simulated fracture structure, the two side baffles, and the inlet (outlet) liquid tank of the present invention; Figure 6 It is a schematic diagram of the rough wall surface of the simulated fracture for 3D printing of the present invention; Figure 7 It is a schematic diagram of the external fixture structure of the simulated filled fracture model of the present invention; Figure 8 It is a schematic diagram of the camera fixture structure of the present invention.

[0018] In the figure: 1 - support bottom plate, 2 - support vertical rod, 3 - liftable support platform, 4 - Mariotte bottle, 5 - flowmeter, 6 - pressure sensor, 7 - light source, 8 - diffuser plate, 9 - simulated filled fracture model, 10 - high-speed camera, 11 - camera fixture, 12 - waste liquid collection tank, 13 - syringe, 14 - injection pump, 15 - main controller, 16 - flowmeter inlet, 17 - flow adjustment knob, 18 - flowmeter outlet, 19 - hose, 20 - slidable rod clamp, 21 - fastening screw, 22 - square connecting rod, 23 - Mariotte bottle support plate, 24a - upper plate of the transparent simulated fracture structure, 24b - lower plate of the transparent simulated fracture structure, 25 - two side baffles, 26 - inlet liquid tank, 27 - first inlet of the fracture model, 28 - outlet liquid tank, 29 - outlet of the fracture model, 30 - second inlet of the fracture model, 31 - particle filling, 32 - metal gasket, 33 - transparent square glass plate, 34 - metal square ring, 35 - vertical long screw, 36 - middle frame, 37 - horizontal long screw, 38 - middle frame support plate, 39 - fracture model carrier, 40 - carrier support vertical rod, 41 - circular connecting rod, 42 - horizontal displacement slide, 43 - vertical displacement slide, 44 - camera clamping slide, 45 - slide rail, 46 - sliding block, 47 - sliding adjustment screw. Detailed implementation manners

[0019] To make the purposes, technical solutions, and advantages of the embodiments of the present invention clearer, the following will combine the accompanying Figure 1-8 drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention.

[0020] As Figure 1 and Figure 2As shown in the figure, a visual experimental system for multiphase flow in a variable-structure simulated fracture under a dynamic water environment includes a hydrodynamic control module, a transparent simulated filled fracture model, a visual observation module, and a rod frame support structure. The hydrodynamic control module is connected to the transparent simulated filled fracture model. The transparent simulated filled fracture model is arranged on the bottom plate of the rod frame support structure. The visual observation module is installed on the top of the rod frame support structure and is connected to the main controller. The hydrodynamic control module is installed on a liftable support platform 3. The hydrodynamic control module includes a Mariotte bottle 4 installed on the top of the liftable support platform and a flowmeter 5 installed on the bottom of the liftable support platform. The Mariotte bottle is connected to the first liquid inlet 27 of the transparent simulated filled fracture model through a first hose 19a. The flowmeter is installed on the first hose. A flow rate adjustment knob 17 is provided on the flowmeter 5 for monitoring and further regulating the dynamic water flow rate. A first pressure sensor 6a is installed on the first hose between the flowmeter and the simulated fracture model for monitoring the dynamic water pressure. The hydrodynamic control module further includes an injection pump 13. The injection pump 13 is composed of a syringe and a stepper motor. The syringe is pushed by the stepper motor to achieve a constant injection flow rate condition. The flow rate is adjusted by changing the propulsion speed of the stepper motor and the type of syringe. The liquid outlet of the syringe is connected to the second liquid inlet 30 of the fracture model. A second pressure sensor 6b is arranged between the liquid outlet of the syringe and the second liquid inlet 30 of the fracture model for monitoring the injection pressure of the second-phase liquid. The flowmeter, the first pressure sensor, the stepper motor, and the second pressure sensor are all connected to the main controller, realizing the adjustment and control of the dynamic water pressure, the dynamic water flow rate, and the injection flow rate of the second-phase liquid.

[0021] The main controller of the present invention selects a commercially available industrial computer.

[0022] The visual experimental system for multiphase flow in a variable-structure simulated fracture under a dynamic water environment according to the present invention, as Figures 3-5 The simulated filled fracture model 9 includes a transparent simulated fracture structure, a granular filler 31, two side baffles 25, a liquid inlet groove 26, a liquid outlet groove 28, an external fixture of the model, and a waste liquid collection tank 12. The liquid inlet 27 and the liquid outlet 29 of the transparent simulated fracture structure are respectively butted with the liquid inlet groove and the liquid outlet groove. The two sides are respectively butted with the two side baffles. Sealing rubber strips are pasted on the contact surfaces of the liquid inlet groove, the liquid outlet groove, the two side baffles and the fracture structure, and they are placed together in the center of the external fixture of the model and fixed and sealed by means of screw extrusion.

[0023] The visual experimental system for multiphase flow in a variable-structure simulated fracture under a dynamic water environment according to the present invention, as Figure 5As shown, the transparent simulated fracture structure includes an upper plate 24a and a lower plate 24b of the transparent simulated fracture, which are made by replicating fracture specimens with different rough structures and sizes and using transparent epoxy resin or glass materials; after replication, the two long sides of the upper and lower plates of the fracture are polished to form two gasket platforms; a second liquid inlet 30 is provided at the middle position of the fracture model, which is connected to the liquid outlet of the syringe through a third hose 19c; a high-strength metal gasket 32 is placed on the gasket platform of the lower plate of the fracture, its length is equal to the length of the fracture structure, and its width is equal to the width of the gasket platform. Different gasket thicknesses are used to adjust the aperture of the fracture structure and the size of the internal cavity; the granular filling material 31 is placed on the surface of the lower plate of the fracture, and the filling degree is controlled by changing the ratio of the apparent volume of the filling material to the cavity volume. Subsequently, the upper and lower plates of the fracture are joined together to form a transparent simulated fracture structure.

[0024] In the variable-structure simulated fracture multiphase flow visualization test system under dynamic water environment of the present invention, the granular filling material 31 selects different types and materials according to the test purpose; when the test focuses on the fluid flow law in the filled fracture, the granular filling material selects gas-phase silica powder and transparent quartz sand with refractive index matching the fluid; when the test focuses on the erosion and loss of particulate matter in the filled fracture, the granular filling material selects PE microspheres, silicon powder, and colored transparent model sand, and the fluid is colorless, and the loss degree of particulate matter is judged by observing the change of light intensity in the fracture model based on the optical principle.

[0025] In the variable-structure simulated fracture multiphase flow visualization test system under dynamic water environment of the present invention, the liquid inlet tank 26 and the liquid outlet tank 28 have the same structure, their width is equal to the width of the fracture structure, and their thickness is equal to the thickness of the joined fracture structure; the side in contact with the fracture structure of the liquid inlet and outlet tanks is an open-space structure, and its size is larger than the effective flow-through surface of the fracture structure; a first liquid inlet 27 is provided on the other side of the liquid inlet tank that is not in contact with the fracture structure, which is connected to a flow meter through a first hose 19a; similarly, a liquid outlet 29 is provided on the other side of the liquid outlet tank that is not in contact with the fracture structure, which discharges the test fluid and the granular filling material into a waste liquid collection tank through a second hose 19b; the two side baffles 25 have the same structure, their length is equal to the length of the fracture structure, their width is 1 cm, and their height is equal to the thickness of the joined fracture structure, and they are mainly used to squeeze and stop water on the side.

[0026] In the variable-structure simulated fracture multiphase flow visualization test system under dynamic water environment of the present invention, as Figure 7As shown in the figure, the external fixture of the model includes an upper fixture, a middle frame 36, and a lower fixture; the upper fixture and the lower fixture are symmetric in structure and are composed of an embedded transparent square glass plate 33 and a metal square ring 34. The size of the transparent square glass plate is larger than that of the transparent simulated fracture structure to ensure effective observation of the flow process. A set of vertical threaded through-holes are provided around the metal square ring of the upper fixture, and corresponding vertical threaded holes are provided at the same positions on the metal square ring of the lower fixture. The transparent simulated fracture structure in the middle is locked with the upper and lower fixtures through vertical long screws 35 to ensure that the aperture of the fracture structure remains unchanged. An adjustable-height middle frame support plate 38 is provided outside the lower fixture to support the middle frame and ensure that its horizontal center is consistent with the horizontal center of the transparent simulated fracture structure. A set of horizontal threaded holes are provided in the middle frame, and the side baffles, the liquid inlet groove, and the liquid outlet groove are respectively fixed around the transparent simulated fracture structure through horizontal long screws 37. To avoid mutual interference, the positions of the horizontal threaded through-holes are staggered with the positions of the vertical threaded holes in the upper and lower fixtures.

[0027] For the simulated fracture multiphase flow visualization test system with variable structure under dynamic water environment of the present invention, the visualization observation module includes a high-speed camera 10, a diffuser plate 8, a light source 7, and a main controller 15; the high-speed camera 10 is placed above the simulated filled fracture model and fixed by a camera fixture 11 in the rod support structure; the diffuser plate and the light source are arranged in sequence below the fracture model, and the two are adhesively connected by four plastic short columns and are integrally placed on the support bottom plate 1b of the rod support structure; a round hole is opened in the center of the diffuser plate, and the third hose connected to the second liquid inlet passes through the round hole, the middle part between the light source and the diffuser plate, and is connected to a syringe, so as to hide the third hose in the camera photo, facilitating accurate observation, processing, and analysis of the fluid flow process; the high-speed camera, the fracture model, the diffuser plate, and the light source are arranged collinearly centered vertically, and the high-speed camera is connected to the main controller.

[0028] For the simulated fracture multiphase flow visualization test system with variable structure under dynamic water environment of the present invention, the rod support structure includes a support bottom plate 1, a fracture model carrier 39, two camera support vertical rods 2, four carrier support vertical rods 40, and a three-dimensionally adjustable camera fixture 11; the camera support vertical rods 2 and the carrier support vertical rods 40 are respectively threadedly connected and fixed to the support bottom plate, and then are respectively connected to the camera fixture and the fracture model carrier; a square hole is opened at the center of the fracture model carrier 39, the size of the square hole is larger than the size of the transparent square glass plate embedded in the lower fixture of the fracture model and smaller than the size of the metal square ring in the lower fixture of the fracture model, so as to place the fracture model and enable the lower light source to pass through the square hole and enter the fracture model.

[0029] For the simulated fracture multiphase flow visualization test system with variable structure under dynamic water environment of the present invention, as Figure 8As shown in the figure, the three-dimensional adjustable camera fixture includes a slidable rod clamp 20b, a circular connecting rod 41, a lateral displacement slide 42, a vertical displacement slide 43, and a camera clamping slide 44; the slidable rod clamp sleeve 20b is on the support vertical rod and has a circular rod hole in the middle; one side of the circular connecting rod 41 is connected to the back of the lateral displacement slide and fixed by a screw on the circular rod hole; the lateral displacement slide, the vertical displacement slide, and the camera clamping slide are respectively composed of a slide rail 45, a sliding block 46, and a sliding adjustment screw 47, and the sliding block is adjusted to move by the sliding adjustment screw; the sliding block on the front of the lateral displacement slide is connected to the back of the vertical displacement slide, and the sliding block on the front of the vertical displacement slide is connected to the back of the camera clamping slide; the slider of the camera clamping slide is composed of two left and right side plates, and the camera is fixed by a clamping method; the lateral displacement slide, the vertical displacement slide, and the camera clamping slide are arranged in a cross in space; the camera is fixed to a suitable height by the slidable rod clamp, and the sliding adjustment screws on the circular connecting rod and the lateral and vertical displacement slides are used to realize the rapid adjustment of the camera in three-dimensional space, so as to facilitate the adjustment of the camera's field of view, image focusing, and to achieve the vertical central collinearity with the fracture model and the light source.

[0030] For the simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment of the present invention, the fracture specimens with different rough structures and sizes can be prepared by one of the following two methods: 1 Method 1: Select the rock type according to the research needs, cut the collected rock according to the set size, and then use the Brazilian splitting method to prepare rock fracture specimens with different rough structures and sizes; the roughness of the obtained fracture wall is mainly related to the coarse particle composition inside the rock. Generally, the order of the wall roughness size is: granite > marble > sandstone > shale; 2 Method 2: Conduct morphological statistics on the rock structure after splitting the sample to be measured, extract its characteristic parameters such as the average protrusion height and height variation coefficient, and then based on the fracture structure surface power spectrum function and random seed method proposed by Brown, write the random generation code for the simulated fracture morphology, adjust the Hurst index in the power spectrum function through analog statistical analysis, obtain the simulated rough fracture wall structure, and then combine with 3D printing technology to obtain the printed rock fracture specimens with different rough structures and sizes. For example, Figure 6 shows the schematic diagrams of two different sizes of simulated fracture rough walls under the condition of Hurst index H = 0.7 - 0.9.

[0031] The method for conducting tests on the simulation fracture multiphase flow visualization test system with variable structure under dynamic water environment of the present invention is characterized by including the following steps: S1. Install the liftable support platform 3 and the rod frame support structure: Connect the support base plate 1 and the support vertical rod 2 together through a threaded structure, adjust the level of the support base plate and the verticality of the support vertical rod, and then connect the slidable rod clamp 20, the Mariotte bottle support structure, the fissure model carrier 39, and the camera clamp 11; S2. Install the transparent simulated filled fissure model: Mold the upper plate 24a and the lower plate 24b of the transparent simulated fissure structure, select the appropriate filling type and volume 31 and the thickness of the metal gasket 32 according to the test purpose and working conditions, then assemble the simulated fissure structure and place it on the lower clamp; Adjust the height of the middle frame 36 according to the thickness of the assembled fissure structure, and fix the liquid inlet groove, the liquid outlet groove, and the two side baffles to the fissure model through the horizontal screws of the middle frame, then install the upper clamp, tighten the screws, completely fix the fissure structure at the center of the clamp, and test the airtightness of the model; Place the assembled transparent simulated filled fissure model on the carrier; S3. Install the visualization observation module: Fix the high-speed camera 10 through the camera clamp 11 and adjust it to an appropriate height, paste the support short column between the diffuser plate 8 and the light source 7, and place the whole on the support base plate 1, adjust the positions of the camera, the transparent simulated filled fissure model, the diffuser plate, and the light source so that they are collinear at the center in the vertical direction; S4. Install the hydrodynamic control module: Install the Mariotte bottle 4, the injection pump 13, the flowmeter 5, the first pressure sensor 6a, and the second pressure sensor 6b, connect the first hose, the second hose, and the third hose respectively, and check the airtightness of the entire flow channel; The flowmeter, the first pressure sensor, the stepper motor, the second pressure sensor, and the high-speed camera are all connected to the main controller, realizing the regulation and control of the hydrodynamic pressure, the hydrodynamic flow rate, and the injection flow rate of the second-phase liquid; S5. Set the initial test conditions and start the test: According to the test working conditions, set the height of the Mariotte bottle 4, the knob of the flowmeter 5, the injection flow rate of the injection pump 13, the frame rate of the high-speed camera 10, and the intensity of the light source 7, turn on the first pressure sensor and the second pressure sensor, open the Mariotte bottle until the hydrodynamic water saturates the model, and then turn on the high-speed camera to take pictures and open the injection pump; S6. End of the test: Close the Mariotte bottle 4 and the flow pipeline, remove the fissure model 9, then disassemble the fissure model, and clean and dry it; According to the test working conditions, repeat steps S2 and S5 to carry out the next group of tests.

[0032] The above are only the preferred embodiments of the present invention. It should be noted that for those skilled in the art, without departing from the overall concept of the present invention, several changes and improvements can still be made, and these should also be regarded as the protection scope of the present invention.

Claims

1. A simulation fractured multiphase flow visualization test system with a variable structure under a dynamic water environment, characterized in that: It includes a hydrodynamic control module, a transparent simulated filled fracture model, a visualization observation module and a rod frame support structure; the hydrodynamic control module is connected to the transparent simulated filled fracture model, the transparent simulated filled fracture model is arranged on the bottom plate of the rod frame support structure, the visualization observation module is installed on the top of the rod frame support structure, and the visualization observation module is connected to the main controller; the hydrodynamic control module is installed on a liftable support platform (3), the hydrodynamic control module includes a Mariotte bottle (4) installed on the top of the liftable support platform and a flowmeter (5) installed on the bottom of the liftable support platform, the Mariotte bottle is connected to the first liquid inlet (27) of the transparent simulated filled fracture model through a first hose (19a), the flowmeter is installed on the first hose, a flow regulating knob (17) is provided on the flowmeter (5) for monitoring and further regulating the dynamic water flow, and a first pressure sensor (6a) is installed on the first hose between the flowmeter and the simulated fracture model for monitoring the dynamic water pressure; the hydrodynamic control module further includes an injection pump (14), the injection pump (14) consists of a syringe (13) and a stepper motor, and the syringe is pushed by the stepper motor to achieve a constant injection flow condition, and the flow rate is adjusted by changing the propulsion speed of the stepper motor and the type of syringe, and the liquid outlet of the syringe is connected to the second liquid inlet (30) of the fracture model; a second pressure sensor (6b) is arranged between the liquid outlet of the syringe and the second liquid inlet (30) of the fracture model for monitoring the injection pressure of the second-phase liquid; the flowmeter, the first pressure sensor, the stepper motor and the second pressure sensor are all connected to the main controller (15), realizing the regulation and control of the dynamic water pressure, the dynamic water flow and the injection flow of the second-phase liquid.

2. The visualized experimental system for multiphase flow in simulated fractures with variable structures under a moving water environment according to claim 1, wherein: The simulated filled fracture model (9) includes a transparent simulated fracture structure, particulate fillers (31), side baffles (25), a liquid inlet groove (26), a liquid outlet groove (28), an external fixture for the model, and a waste liquid collection tank (12); the inlet (27) and outlet (29) of the transparent simulated fracture structure are respectively docked with the liquid inlet groove and the liquid outlet groove, and its two sides are respectively docked with the side baffles. Waterproof rubber strips are pasted on the contact surfaces of the liquid inlet groove, the liquid outlet groove, the side baffles and the fracture structure, and they are placed together in the center of the external fixture for the model, and are fixed and sealed against water by means of screw extrusion; the transparent simulated fracture structure includes a transparent simulated fracture hanging wall (24a) and a footwall (24b), which are made by casting a mold of fracture specimens with different rough structures and sizes, and using transparent epoxy resin or glass materials; after casting the mold, the long sides of the upper and lower fracture plates are polished to form two gasket platforms; a second liquid inlet (30) is provided at the middle position of the fracture model, which is connected to the liquid outlet of the syringe through a third hose (19c); high-strength metal gaskets (32) are placed on the gasket platforms of the fracture footwall, the length of which is equal to the length of the fracture structure, and the width is equal to the width of the gasket platform. Different gasket thicknesses are used to adjust the aperture of the fracture structure and the size of the internal cavity; the particulate fillers (31) are placed on the surface of the fracture footwall, and the filling degree is controlled by changing the ratio of the apparent volume of the filler to the cavity volume. Subsequently, the upper and lower fracture plates are assembled to form a transparent simulated fracture structure.

3. The visualized experimental system for multiphase flow in simulated fractures with variable structures under a moving water environment according to claim 2, wherein: The particulate fillers (31) are selected with different types and materials according to the test purpose; when the test research focuses on the fluid flow law in the filled fracture, the particulate fillers are selected as gas-phase silica powder and transparent quartz sand with refractive index matching the fluid; when the test research focuses on the erosion and loss of particulate matter in the filled fracture, the particulate fillers are selected as PE microspheres, silicon powder, and colored transparent model sand, and the fluid is colorless, and the loss degree of particulate matter is judged by observing the change of light intensity in the fracture model based on the optical principle.

4. The visualized test system for multiphase flow in a simulated fracture with a variable structure under a dynamic water environment according to claim 3, wherein: The liquid inlet groove (26) and the liquid outlet groove (28) have the same structure, the width of which is equal to the width of the fracture structure, and the thickness is equal to the thickness of the assembled fracture structure; the side in contact with the fracture structure of the liquid inlet and outlet grooves is an open space structure, and the size is larger than the effective flow-through surface of the fracture structure; a first liquid inlet (27) is provided on the other side of the liquid inlet groove that is not in contact with the fracture structure, which is connected to a flow meter through a first hose (19a); similarly, a liquid outlet (29) is provided on the other side of the liquid outlet groove that is not in contact with the fracture structure, and the test fluid and the particulate fillers are discharged into the waste liquid collection tank through a second hose (19b); the two side baffles (25) have the same structure, the length of which is equal to the length of the fracture structure, the width is 1 cm, and the height is equal to the thickness of the assembled fracture structure, and it mainly squeezes the water stop with the side.

5. The visualized experimental system for multiphase flow in simulated fractures with variable structures under a hydrodynamic environment according to claim 4, wherein: The external fixture of the model includes an upper fixture, a middle frame (36) and a lower fixture; the upper fixture and the lower fixture are symmetric in structure and are composed of an embedded transparent square glass plate (33) and a metal square ring (34). The size of the transparent square glass plate is larger than that of the transparent simulated fracture structure, so as to ensure the effective observation of the flow process. A group of vertical threaded through-holes are provided around the metal square ring of the upper fixture, and corresponding vertical threaded holes are provided at the same positions on the metal square ring of the lower fixture. The transparent simulated fracture structure in the middle is locked with the upper and lower fixtures through vertical long screws (35) to ensure that the aperture of the fracture structure remains unchanged. An adjustable-height middle frame support plate (38) is provided outside the lower fixture to support the middle frame and ensure that its horizontal center is consistent with the horizontal center of the transparent simulated fracture structure. The middle frame is provided with a group of horizontal threaded holes, and the side baffles, the liquid inlet groove and the liquid outlet groove are respectively fixed around the transparent simulated fracture structure through horizontal long screws (37). To avoid mutual interference, the positions of the horizontal threaded through-holes are arranged staggeredly with the positions of the vertical threaded holes in the upper and lower fixtures.

6. The visualization test system for simulated fractured multiphase flow with variable structure under a dynamic water environment according to claim 5, wherein: The visual observation module includes a high-speed camera (10), a diffuser plate (8), and a light source (7); the high-speed camera (10) is placed above the simulated filled fracture model and fixed by a camera fixture (11) in the rod support structure. The diffuser plate and the light source are arranged in sequence below the fracture model, and the two are adhesively connected by four plastic short columns and are integrally placed on the support bottom plate (1b) of the rod support structure. A round hole is opened in the center of the diffuser plate, and the third hose connected to the second liquid inlet passes through the round hole, the middle part of the light source and the diffuser plate, and is connected to the syringe, so as to hide the third hose in the camera photo, facilitating the accurate observation, processing and analysis of the fluid flow process. The high-speed camera, the fracture model, the diffuser plate and the light source are arranged collinearly centered in the vertical direction, and the high-speed camera is connected to the main controller.

7. The visualization test system for simulated fractured multiphase flow with variable structure under dynamic water environment according to claim 1, characterized in that: The rod support structure includes a support bottom plate (1), a fracture model carrier (39), two camera support vertical rods (2), four carrier support vertical rods (40), and a three-dimensionally adjustable camera fixture (11); the camera support vertical rods (2) and the carrier support vertical rods (40) are respectively threadedly connected and fixed to the support bottom plate, and then are respectively connected to the camera fixture and the fracture model carrier. A square hole is opened at the center of the fracture model carrier (39), and the size of the square hole is larger than the size of the transparent square glass plate embedded in the lower fixture of the fracture model and smaller than the size of the metal square ring in the lower fixture of the fracture model, so as to place the fracture model and allow the lower light source to pass through the square hole and enter the fracture model.

8. The visualization test system for simulated fractured multiphase flow with variable structures under a dynamic water environment according to claim 7, characterized in that: The three-dimensional adjustable camera fixture includes a slidable rod clamp (20b), a circular connecting rod (41), a lateral displacement slide (42), a vertical displacement slide (43), and a camera clamping slide (44); the slidable rod clamp sleeve (20b) is on the support vertical rod and has a circular rod hole in the middle; one side of the circular connecting rod (41) is connected to the back of the lateral displacement slide and fixed by a screw on the circular rod hole; the lateral displacement slide, the vertical displacement slide, and the camera clamping slide are respectively composed of a slide rail (45), a sliding block (46), and a sliding adjustment screw (47), and the sliding block is adjusted to move by the sliding adjustment screw; the sliding block on the front of the lateral displacement slide is connected to the back of the vertical displacement slide, and the sliding block on the front of the vertical displacement slide is connected to the back of the camera clamping slide; the sliding block of the camera clamping slide is composed of left and right side plates, and the camera is fixed by a clamping method; the lateral displacement slide, the vertical displacement slide, and the camera clamping slide are arranged in a cross shape in space; the camera is fixed to a suitable height by the slidable rod clamp, and the sliding adjustment screws (47) on the circular connecting rod and the lateral and vertical displacement slides are used to quickly adjust the camera in three-dimensional space, so as to facilitate the adjustment of the camera's field of view, image focusing, and to achieve the vertical central collinearity with the fracture model and the light source.

9. The simulated fractured multiphase flow visualization test system with variable structure under dynamic water environment according to claim 2, wherein: The fracture specimens with different rough structures and sizes can be prepared by one of the following two methods: 1) Method 1: Select the rock type according to the research needs, cut the collected rock according to the set size, and then use the Brazilian splitting method to prepare rock fracture specimens with different rough structures and sizes; the roughness of the obtained fracture wall is mainly related to the coarse particle composition inside the rock. Generally, the order of the wall roughness is: granite > marble > sandstone > shale; 2) Method 2: Conduct a morphology statistics on the sample to be measured, extract its characteristic parameters, Subsequently, based on the fracture structural plane power spectrum function and the random seed method proposed by Brown, write the simulation fracture morphology random generation code, adjust the Hurst exponent in the power spectrum function through analog statistical analysis, obtain the simulated rough fracture wall structure, and then combine with 3D printing technology to obtain the printed rock fracture specimens with different rough structures and sizes.

10. A method for conducting experiments using the simulation fractured multi-phase flow visualization test system with variable structures under a dynamic water environment according to any one of claims 1-9, characterized in that, It includes the following steps: S1. Install the liftable support platform (3) and the rod frame support structure: Connect the support bottom plate (1) and the support vertical rod (2) together through a threaded structure, adjust the level of the support bottom plate and the verticality of the support vertical rod, and then connect the slidable rod clamp (20), the Mariotte bottle support structure, the fracture model carrier (39), and the camera fixture (11); S2. Install the transparent simulation filling fracture model: Mold the upper (24a) and lower plates (24b) of the transparent simulation fracture structure. Select the appropriate filling type and volume (31) and the thickness of the metal gasket (32) according to the test purpose and working conditions. Then, assemble the simulation fracture structure and place it on the lower fixture. Adjust the height of the middle frame (36) according to the thickness of the assembled fracture structure, and fix the liquid inlet tank, liquid outlet tank, and side baffles to the fracture model through the horizontal screws of the middle frame. Then, install the upper fixture, tighten the screws, completely fix the fracture structure at the center of the fixture, and test the airtightness of the model. Place the assembled transparent simulation filling fracture model on the stage. S3. Install the visualization observation module: Fix the high-speed camera (10) through the camera fixture (11) and adjust it to the appropriate height. Paste the support short columns between the diffuser plate (8) and the light source (7), and place the whole on the support base plate (1). Adjust the positions of the camera, transparent simulation filling fracture model, diffuser plate, and light source so that they are collinear at the center in the vertical direction. S4. Install the hydrodynamic control module: Install the Mariotte bottle (4), injection pump (14), flowmeter (5), first pressure sensor (6a), and second pressure sensor (6b). Connect the first hose, second hose, and third hose respectively, and check the airtightness of the entire flow channel. The flowmeter, first pressure sensor, stepper motor, second pressure sensor, and high-speed camera are all connected to the main controller, realizing the regulation and control of the dynamic water pressure, dynamic water flow, and the injection flow of the second-phase liquid. S5. Set the initial test conditions and start the test: According to the test working conditions, set the height of the Mariotte bottle (4), the knob of the flowmeter (5), the injection flow of the injection pump (14), the frame rate of the high-speed camera (10), and the intensity of the light source (7). Turn on the first pressure sensor and the second pressure sensor, open the Mariotte bottle until the model is saturated by the dynamic water, then turn on the high-speed camera to take pictures and open the injection pump. S6. End of the test: Close the Mariotte bottle (4) and the flow pipeline, remove the fracture model (9), then disassemble the fracture model, and clean and dry it. According to the test working conditions, repeat steps S2 and S5 to conduct the next set of tests.

Images