Experimental device and method for visualizing flow of pore fluid in medium

Abstract

The invention discloses an experimental device and method for visualizing flow of pore fluid in a medium. The device comprises a schlieren imaging module, an image recording module and an image processing module, the schlieren imaging module comprises a light source, a first convex lens, a second convex lens and a pore flow field model; wherein the light source is arranged on one side of the first convex lens, the pore flow field model is arranged on the other side of the first convex lens, and light passes through the first convex lens and then penetrates through the pore flow field model to form interference fringes; the pore model flow field is arranged between the first convex lens and the second convex lens and is used for simulating speed distribution and a vortex structure of fluid in a pore medium; the image recording module is arranged at the output end of the schlieren imaging module and used for collecting and recording interference fringe images formed by the schlieren imaging module so that the image processing module can be used for analyzing and displaying pore fluid flow in the medium.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of rock physics, and in particular to an experimental device and method for visualizing the flow of pore fluid in a medium. BACKGROUND

[0002] The behavior of fluid in porous media is crucial for evaluating the characteristics of reservoirs, predicting the flow of oil and gas, and conducting seismic wave exploration. Currently, commonly used theoretical models for studying pore fluid include the Biot model and the jet flow model. These models are based on idealized assumptions, such as the assumption of uniform pore channel flow and constant pressure boundary conditions. However, fluid flow in actual porous media is more complex, with cases of axial global flow and local reverse flow. In addition, the flow is more complex in the case of diverse pore structures. Therefore, theoretical models based on idealized assumptions cannot accurately describe the fluid motion and wave field dispersion and attenuation in complex porous media.

[0003] In order to verify and improve theoretical models and provide more accurate descriptions and predictions of fluid motion behavior in porous media, it is necessary to directly observe the flow field of pore fluid. Direct observation of the flow field of pore fluid can provide real-time flow field information, directly observe the flow behavior, and provide more direct evidence for understanding the relationship between pore structure parameters and fluid flow properties.

[0004] Therefore, it is urgent to realize a device and method that can observe the change of pore fluid flow field in real time to solve the problem that traditional methods cannot directly observe the behavior of fluid in porous media. SUMMARY

[0005] The present disclosure provides an experimental device and method for visualizing the flow of pore fluid in a medium, which can directly observe and display the flow field of fluid in complex pore structures.

[0006] In a first aspect, the present disclosure provides an experimental device for visualizing the flow of pore fluid in a medium, comprising a schlieren imaging module, an image recording module, and an image processing module. The schlieren imaging module comprises a light source, a first convex lens, a second convex lens, and a pore model flow field. The light source is arranged on one side of the first convex lens, and the pore model flow field is arranged on the other side of the first convex lens to form interference fringes through the pore model flow field. The pore model flow field is arranged between the first convex lens and the second convex lens to simulate the velocity distribution and vortex structure of fluid in porous media. The image recording module is arranged at the output end of the schlieren imaging module to capture and record the interference fringe images formed by the schlieren imaging module. The image processing module is used to analyze and display the flow field of the interference fringe images.

[0007] In a second aspect, the embodiments of the present application further provide an experimental method for visualizing fluid flow in pores of a medium, which applies the experimental device for visualizing fluid flow in pores of a medium according to any one of the above embodiments; the method comprises the following steps:

[0008] An experimental device for visualizing fluid flow in pores of a non-uniform medium is built, and the experimental device is calibrated;

[0009] Fluid is injected into the pore model in the calibrated experimental device, and the fluid flow process is collected and video data is recorded by using the image recording module;

[0010] Flow field analysis of the fluid is performed according to the recorded video data by using the image processing device, and a flow field vector diagram is generated.

[0011] Compared with the related art, the present application provides an experimental device and method for visualizing fluid flow in pores of a medium, which comprises a schlieren imaging module, an image recording module and an image processing module; the schlieren imaging module comprises a light source, a first convex lens, a second convex lens and a pore flow field model; wherein: the light source is arranged on one side of the first convex lens, the pore flow field model is arranged on the other side of the first convex lens, and light passes through the pore flow field model to form interference fringes after passing through the first convex lens; the pore flow field model is arranged between the first convex lens and the second convex lens, and is used to simulate the velocity distribution and vortex structure of fluid in a pore medium; the image recording module is arranged at the output end of the schlieren imaging module, and is used to collect and record the interference fringe images formed by the schlieren imaging module, so as to analyze and display the fluid flow in pores of the medium by using the image processing module. The device can be used to directly observe the fluid flow field in a complex pore structure by using time resolution schlieren imaging technology.

[0012] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art, and will be learned from the practice of the present application. Other advantages of the present application will be realized and attained by the methods and solutions described in the specification and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings are included to provide an understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, for explaining the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0014] Figure 1 The experimental device for visualizing fluid flow in pores of a medium according to the embodiments of the present application is shown in the figure;

[0015] Figure 2 The experimental method for visualizing fluid flow in pores of a medium according to the embodiments of the present application is shown in the figure;

[0016] Figure 3 Overall schematic diagram of experimental setup for visualization of pore fluid flow in the medium for some example embodiments;

[0017] Figure 4 Schematic diagram of variable-pore-size sinusoidal-walled tube pore model structure for some example embodiments;

[0018] Figure 5 Actual photograph of acrylic variable-pore-size sinusoidal-walled tube pore model for some example embodiments;

[0019] Figure 6 Actual photograph of experimental setup based on the acrylic variable-pore-size sinusoidal-walled tube pore model for some example embodiments;

[0020] Figure 7 Flow field diagram of pore model with hot water injected from the left-side inlet for some example embodiments;

[0021] Figure 8 Flow field diagram of pore model with hot water injected from the right-side inlet for some example embodiments Figure 1 ;

[0022] Figure 9 Flow field diagram of pore model with hot water injected from the right-side inlet for some example embodiments Figure 2 ;

[0023] Figure 10 Flow field diagram of pore model with hot water injected from the right-side inlet for some example embodiments Figure 3 ;

[0024] Figure 11 Flow field diagram of pore model with fluid injected from the right-side inlet for some example embodiments. DETAILED DESCRIPTION

[0025] The present application describes a number of embodiments, but the description is illustrative rather than limiting and many additions, deletions, and modifications can be made to the described embodiments without departing from the scope of the application described herein. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are possible. Any feature of any embodiment can be used with any other feature or combination of features from any other embodiment, or in the alternative, can replace any other feature or combination of features in any other embodiment, unless specifically restricted otherwise.

[0026] This application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features, and elements disclosed herein can also be combined with any conventional feature or element to form a unique application within the scope of the claims. Any feature or element of any embodiment can also be combined with features or elements from other application schemes to form another unique application within the scope of the claims. Therefore, it is to be understood that any feature shown and / or discussed in this application can be implemented alone or in any suitable combination. Embodiments are, therefore, not to be limited to the specific embodiments disclosed herein, but only to the extent allowed by the appended claims and their equivalents. Further, various modifications and changes can be made thereto within the scope and spirit of the claims.

[0027] Furthermore, in describing representative embodiments, the specification can have presented the method and / or process as a particular sequence of steps. However, to the extent that the method or process depends on more than one step, the method or process should not be limited to the particular sequence of steps described. Other sequences of steps can be possible, depending on the particular application or implementation, and the sequence of steps need not be performed in the order presented. The specific order of steps presented in the specification is not to be construed as a limitation, but is presented for illustrative purposes. Further, the claims should not be limited to the steps of the method and / or process in the order presented, as they can be readily changed in order to adapt them to different applications and / or implementations.

[0028] There are currently some direct observation methods for pore flow field, such as:

[0029] Nuclear Magnetic Resonance Imaging (NMRI). Using nuclear magnetic resonance technology to observe the distribution and flow of fluid in the pore medium. By applying a magnetic field and pulse sequence to the sample, the signal of the fluid in the pore can be obtained, and the flow field information can be restored. This method can provide high-resolution fluid images, but is limited by the size of the sample and the structure of the pore.

[0030] X-ray Computed Tomography (CT). Using X-ray absorption and scattering through the sample, a three-dimensional image of the sample is reconstructed. By scanning the fluid sample, the distribution and flow of fluid in the pore medium can be observed. This method has the characteristics of high resolution and non-destructive, but the resolution of multiphase flow is low, and it cannot provide fluid velocity information.

[0031] Microscopic visualization experiments. Flow phenomena in porous media are observed through a microscope. A common method is to use transparent model materials, such as glass micro-models or transparent polymers, to make a model of the porous medium, and observe the movement of fluid in the pores under a microscope. This method can provide intuitive flow images, but is limited by model size and microscope resolution.

[0032] The above direct observation methods have some problems and limitations, specifically as follows:

[0033] I. Scale limitation. Existing direct observation methods are generally suitable for micro-scale porous media, and it is difficult to directly observe macro-scale porous flow conditions.

[0034] II. Sampling bias. Due to the limitations of the sample and the limitations of the experimental conditions, the actual observed flow field may not fully represent the flow conditions of the entire porous medium, and there is a sampling bias.

[0035] III. Measurement error. There is a certain measurement error in the observation method itself, such as signal noise, image reconstruction algorithm, etc., which will affect the accuracy and reliability of the flow field.

[0036] IV. Flow condition limitation. Some direct observation methods require certain control and processing of the sample, such as the application of an external field (magnetic field, pressure, etc.), which may change the real conditions of the porous medium flow, resulting in differences between the observed results and the actual situation.

[0037] V. Difficulty in real-time flow observation. The time resolution of techniques such as nuclear magnetic resonance imaging and X-ray computed tomography is not high, and they cannot directly observe and record the transient flow phenomena of the porous flow field.

[0038] In order to achieve direct observation of the porous fluid flow field, the following difficulties need to be faced:

[0039] First, the flow in complex porous media has multi-scale and multi-phase properties, which is difficult to directly observe and measure.

[0040] Second, the permeability and pore structure parameters of the porous medium have a great influence on the flow behavior of the fluid, which requires the design of appropriate experimental methods and technical means to study the flow behavior under different pore structure conditions.

[0041] In addition, factors such as fluid-rock interaction and the influence of experimental environment on flow behavior need to be considered during the experiment to ensure the accuracy and reliability of the experimental results.

[0042] Based on the analysis of the existing problems, the inventors of the present application propose a medium pore fluid flow visualization experimental device and method, which uses schlieren imaging technology to directly observe the time-varying fluid flow field in a variable-diameter pipe.

[0043] This invention provides an experimental apparatus for visualizing pore fluid flow in a medium, such as... Figure 1 As shown, the device includes: a schlieren imaging module 100, an image recording module 110, and an image processing module 120;

[0044] The schlieren imaging module 100 includes: a light source, a first convex lens, a second convex lens, and a pore model flow field;

[0045] in:

[0046] The light source is set on one side of the first convex lens, and a pore model flow field is set on the other side of the first convex lens so as to form interference fringes through the pore model flow field.

[0047] The pore flow field model is set between the first convex lens and the second convex lens to simulate the velocity distribution and vortex structure of the fluid in the porous medium.

[0048] The image recording module is located at the output end of the schlieren imaging module and is used to acquire and record the interference fringe image formed by the schlieren imaging module, so as to use the image processing module to perform flow field analysis and display on the interference fringe image.

[0049] In one exemplary embodiment, this experimental device is based on the fundamental principle of schlieren imaging and is a device that can observe the changes in the flow field in a pore model over time in real time.

[0050] In one exemplary embodiment, an experimental apparatus for visualizing pore fluid flow in a medium, such as... Figure 3 As shown, light source S can provide a certain brightness and a stable light source, such as a 15-watt LED point light source with uniform luminous brightness and a small light source area to ensure the clarity of the schlieren pattern.

[0051] The first convex lens L1 and the second convex lens L2 are two large-aperture convex lenses, and the system also includes an optical path adjustment device. This device is used for focusing, brightness adjustment, and other functions. The optical path adjustment device may include: 1. a lens spatial position fine-tuning platform; 2. a light source intensity control knob.

[0052] In one exemplary embodiment, the position of the light source is determined as follows: the light source is located at the focal point of the first convex lens, so that the light rays form parallel rays after passing through the first convex lens.

[0053] The position of the second convex lens is determined as follows: after the parallel light rays formed by the light source pass through the convex lens, they pass through the flow field region of the pore model to be observed and are focused onto the focal plane of the second convex lens.

[0054] The camera is arranged at the focal point of the second convex lens to capture the fringe image on the schlieren plane. The schlieren plane is a vertical plane behind the second convex lens (away from the light source), and is a series of planes, the farther the imaging, the larger.

[0055] In an example embodiment, the image recording module is a high-speed camera. The Chronos 2.1 high-speed camera is used to record the schlieren image and transmit its signal to the computer through the HDMI interface. After the light passes through the sample, a series of bright and dark images will be formed on the schlieren plane, which can be recorded and saved by the high-speed camera and the large-capacity storage device inside the camera.

[0056] In an example embodiment, the pore flow field model is a variable aperture structure sinusoidal wall pipe pore model; the relative size and geometry of the pore flow field model are determined according to the real pore structure parameters observed in the rock sample picture; the pore structure parameters are determined according to the actual reservoir data and microscopic observation of the rock sample. The pore structure parameters include: pore average radius size, pore wall fluctuation amplitude, pore axial size transformation period characteristic length.

[0057] In an example embodiment, the pore model in the pore model flow field is a variable aperture structure sinusoidal wall pipe pore model, and the wall surface of the variable aperture structure sinusoidal wall pipe pore model satisfies the following conditions:

[0058]

[0059] In the above formula, R i (z) represents the corresponding real pore radius at the axial coordinate z, represents the average pore radius size, A represents the fluctuation amplitude of the variable pore wall surface, represents the fluctuation change period along the axial direction, z represents the axial coordinate of the pore center line, and z0 represents the initial coordinate of the axial reference point. If the coordinate origin is the initial coordinate, then z0=0.

[0060] In this embodiment, the establishment process of the pore flow field model is as follows:

[0061] (1) Determine the model size and geometry:

[0062] According to the real pore structure observed in the rock sample picture, the relative size and geometry of the pore model are formed. The relative size refers to the pore size directly identified from the rock, which is limited by the size of the rock and is generally small, in the order of microns to millimeters. In the experiment, instead of using the pore size directly read from the rock, the size is enlarged by a certain proportion. The relative size refers to the pore size of the rock relative to the experimental sample, which is determined by electron microscopy or CT experiment of rock section. The geometry can also be determined by electron microscopy or CT experiment.

[0063] (2) Determine the pore structure parameters:

[0064] According to the characteristics of the research object, the pore structure parameters are determined, considering the existing material manufacturing technology level and observation effect, the variable diameter sinusoidal wall pipe pore model geometric parameters realized in this example are as follows: Figure 4 As shown in the figure, the parameters are as follows:

[0065] 1-Double inlet spacing 10mm, 2-Double inlet length 15mm, pipe diameter 3mm 3-After the inlet straight pipe length 10mm, pipe diameter 3mm 4-Outlet straight pipe length 16mm, pipe diameter 3mm, 5- Minimum pipe diameter 3mm, 6- Maximum pipe diameter 7mm, 7- Unit length 10mm;

[0066] The total height is 30mm, and the total length is 140mm. This is the real size of the variable diameter sinusoidal wall pipe pore experimental model, which corresponds to the average radius size of the pore, the characteristic length of the axial size transformation period, the fluctuation amplitude of the changing pore wall, etc. Parameters have a decisive role in fluid flow pattern. Some proportional relationship between these parameters is important, such as the proportion between the fluctuation amplitude and the characteristic size of the axial variation period, according to different parameters, different scale fluid flow phenomena can be described.

[0067] (3) Pore model making:

[0068] Pore model making includes material selection, manufacturing process model installation, etc.

[0069] Since the brightness change of light passing through the fluid in the model needs to be observed, suitable materials need to be selected for making the pore model, and transparent materials (acrylic) are used here. As Figure 5The laser cutting and cementing process is selected according to the geometric shape and size of the pore model. In the production process, the geometric accuracy of the pore model is ensured, and the error is minimized to ensure the accuracy of the experimental results. In the experiment, metal screws need to be installed at the fluid inlet and outlet of the model, and the fluid inlet and outlet are formed by silica gel pipes. The pore model is fixed on the adjustable height lifting platform, and the height of the lifting platform is adjusted according to the position of the light to ensure that the position is stable and consistent with the propagation path of the light.

[0070] The experimental device for visualizing the fluid flow in the pores of the medium realized by the embodiment can realize real-time observation of the fluid flow in the medium, and is used for studying the flow behavior under different pore structure conditions. The device directly observes the time-varying fluid flow field in the variable-diameter pipeline by using the schlieren imaging technology.

[0071] The schlieren imaging is an experimental technology based on the interference phenomenon of light, which reflects the changes of fluid density or refractive index by observing the light and dark changes of light. When light passes through regions with different densities or refractive indexes in the flow field, the propagation path of the light will be slightly deviated, thereby forming interference fringes. By recording the changes of the interference fringes, the spatial distribution and changes of the flow field can be obtained.

[0072] In addition, the application also realizes real-time observation and recording of the instantaneous flow field by injecting water with different temperatures into the pore model by using a high-speed camera. The refractive index of the fluid is related to the fluid density, and the fluid density depends on the fluid temperature. Therefore, by injecting hot water into cold water, the fluid density is changed, and then the refractive index of the fluid is changed. Therefore, based on the pore model with the designed sinusoidal wall pipe structure and the fluid refractive index change scheme, simulation of various fluid flows can be realized.

[0073] The embodiment of the application provides a method for visualizing the fluid flow in pores of a medium, as shown in Figure 2 The method comprises steps 200-220.

[0074] Step 200: build an experimental device for visualizing the fluid flow in pores of a medium, and calibrate the experimental device;

[0075] Step 210: inject fluid into the pore flow field model in the experimental device, and simultaneously collect and record the interference fringe image formed during the fluid flow process;

[0076] Step 220: analyze the fluid flow in the pores of the medium according to the recorded image data, generate a flow field vector diagram, and display.

[0077] In an example embodiment, a medium pore fluid flow visualization experimental device is built and calibrated, and the specific implementation steps include:

[0078] First step, determine the light source position and light path design: adjust the position of the light source through the two-dimensional movable slide, ensure that the light is at the focal point position of the first convex lens, and make the light form parallel light after passing through the first convex lens, and pass through the flow field area to be observed.

[0079] Second step, prepare the schlieren plane: place the observed pore model between the first and second convex lenses, and the light parallel through the flow field in the model should ensure that the model surface is smooth and transparent, and does not affect the formation of light propagation and interference phenomenon.

[0080] Third step, adjust the light path and focus: according to the light path design, adjust the position and angle of the second convex lens and the high-speed camera, so that the parallel light can be accurately focused on the focal plane of the second convex lens and enter the high-speed camera lens, ensuring the stability of the light and the formation of clear interference fringes. Here, instead of using the conventional blade light shielding method, a camera shutter blade is used to shield part of the light.

[0081] Fourth step, install high-speed camera and image recording equipment: install the camera at the focal point of the second convex lens to capture the schlieren plane image. Carefully adjust the camera position to ensure that the light can maintain a large brightness while meeting the conditions for schlieren imaging. Connect the camera to the computer HDMI interface, and integrate the input video and image recording equipment recording the experimental site to realize real-time test recording.

[0082] Fifth step, experimental device calibration: after the completion of the construction, the calibration of the experimental device is carried out, including adjusting the light source intensity by the dimmer, the precise calibration of the light path and the calibration of the camera focal length, to ensure the clarity, accuracy and reliability of the imaging.

[0083] In an example embodiment, a fluid is injected into the calibrated pore model in the experimental device, and the image recording module is used to collect and record video data during the fluid flow process, including:

[0084] First step, inject cold water into the first inlet of the calibrated pore model in the experimental device to cool the pore model; the specific experimental process can be:

[0085] 1. Select injection tool

[0086] Select 100ml and 200ml syringes to ensure sufficient capacity and fluid control ability. Before the experiment, make sure the syringe is clean to avoid external contamination affecting the experimental observation results.

[0087] 2. Pre-injection of cold water

[0088] Cold water is injected through one of the inlets to cool the porous model and keep it at a lower temperature. This helps to reduce the temperature gradient and temperature variation interference with the flow field observation.

[0089] Second step, remove the air bubbles in the pores of the porous model using a predetermined method;

[0090] After the cold water injection, it is necessary to ensure that there are no air bubbles in the porous model. The air bubbles can be gradually floated out by slowly injecting cold water, or the air bubbles can be helped to escape by shaking or oscillating. At most one of the three inlets can be connected to the atmosphere, and when the syringe is pulled out and other operations are performed, the suspended hose needs to be clamped with a clamp, and the clamp is removed before injecting hot water to ensure that no air bubbles are introduced into the full water pipe; the pipe is placed vertically, the end of the hot water injection is upward, and the cold water is injected at the lower end to expel the air bubbles and ensure that the pipe is fully cooled and the water in the pipe is cold. A part of the air bubbles will stick to the pipe wall and not be easily expelled, and a part of the small air bubbles can be retained to observe the water flow through the movement of the air bubbles.

[0091] Third step, according to the observation requirements, inject hot water through the second inlet at a predetermined injection rate to simulate different fluid flow modes.

[0092] The injection rate can be adjusted according to the observation requirements, such as slow injection to form laminar flow, or higher rate to form turbulent flow.

[0093] The hose at the end of the hot water injection is as short as possible. When hot water is injected, it may be mixed with cold water in the hose to form warm water in advance, resulting in unclear experimental results; the syringe and hose for injecting hot water are kept in a straight line on the sinusoidal wall pipe; when the hot water injection speed is slow, the clear cold and hot water interface can be seen, and the streak line can be clearly seen, but it is more difficult to push the air bubble movement; when the hot water injection speed is fast, the air bubbles can be better pushed to move with the up and down vortex, and the generated vortex can be seen, but the water in the pipe will quickly become hot water, and the clear streak line cannot be observed. During the hot water injection process, first slowly push the syringe, observe the clear streak line, then gradually increase the speed, and observe the backflow and vortex structure generated on the sinusoidal wall pipe through the movement of the air bubbles, the upper end is clockwise, and the lower end is counterclockwise.

[0094] (3) Fluid supply equipment. Temperature control is the key to the success of schlieren imaging observation, and it is necessary to ensure that the fluid supply equipment can provide stable temperature control to maintain the constant temperature difference of the fluid, and adjust according to the experimental requirements. During the fluid injection process, the pressure of the fluid needs to be controlled to ensure accurate control of the injection rate.

[0095] (4) Fluid containment equipment after fluid flow. According to the experimental requirements and the characteristics of fluid flow, select the appropriate containment equipment to ensure that the fluid can be effectively collected and discharged. After the fluid flows out, it should be collected and properly disposed of.

[0096] In an example embodiment, fluid flow field analysis is performed using the image processing device based on recorded video data, and a flow field vector diagram is generated, including:

[0097] Step 1: Extract feature frame images with flow field characteristics from recorded image data;

[0098] The recorded frame images contain structural features at different times of fluid flow. Among these structural features, some are representative, such as when the fluid enters the control throat from the pore, the flow lines appear perpendicular to the wall surface. In order to display these key structures, a part of the feature frame images is selected from all the recorded frame images for display.

[0099] Step 2: Correct and enhance the feature frame images;

[0100] Step 3: Calculate the processed feature frame images to obtain flow field characteristic parameters;

[0101] In this step, computer vision technology can be used to track the motion and changes of fluid flow, and calculate the flow field characteristic parameters, including flow velocity, vortex structure, flow line trajectory, etc.

[0102] Step 4: Generate a flow field vector diagram based on the flow field characteristic parameters, and display the vector diagram.

[0103] The method of the medium pore fluid flow visualization experiment realized in this embodiment directly verifies the existence of reverse flow and vortex structure in the sine wave wall pipe using experimental means. The existence of these fluid dynamics structures has important influence on fluid velocity and pressure distribution, pore permeability, seismic wave dispersion and attenuation, etc. This experimental device and corresponding experimental method obtain the spatial distribution of the velocity field in the pore model, which helps to determine the fluid flow mechanism in pores with complex geometric structure.

[0104] Example 1

[0105] Based on the basic principle of schlieren imaging, an experimental device is designed to observe the changes of flow field in pore model over time in real time, as shown in Figure 3 The experimental device mainly includes the following components:

[0106] Schlieren imaging module, image recording module and image processing module.

[0107] First part: Schlieren imaging module

[0108] The schlieren imaging module includes: a light source S, a first convex lens L1, a second convex lens L2, and a pore model flow field F.

[0109] As shown in Figure 3 S is a LED point light source. In this experimental device, the light source provides high brightness and stable light source. A 15-watt LED point light source is used, which has uniform luminous brightness and small light source area to ensure the clarity of the schlieren pattern.

[0110] As shown in Figure 3 The schlieren imaging module further includes: two large-aperture convex lenses, L1 and L2 are convex lenses.

[0111] The schlieren imaging device further includes: a pore flow field model. The flow field pore model F: a pore model with a sinusoidal wall pipe shape. The model should consider parameters such as pore size, pore shape, and pore wall characteristics to simulate the actual pore structure.

[0112] Second part: image recording module C

[0113] The image recording module can be a video camera.

[0114] As shown in Figure 3 The image recording module is a high-speed video camera C: a high-speed video camera is used to record time-resolved schlieren imaging of the fluid flow field in the pore fluid model. Ensure that the camera has sufficient frame rate and resolution to capture the instantaneous changes of the flow field.

[0115] Second part: image processing module W

[0116] As shown in Figure 3 The image processing module is a computer W

[0117] The computer W processes and analyzes the images recorded by the schlieren imaging camera. Through data analysis, the spatiotemporal characteristics of pore fluid flow are obtained; the image processing device can quantitatively calculate the velocity spatial distribution of pore space fluid flow, the radius of vortex structure formed by streamlines, and the change trajectory of streamlines from one point to another point in space. Further, the calculated flow field characteristic parameters are used to generate flow field vector diagrams for visual display.

[0118] Example two

[0119] This example shows the visualization experiment process of non-uniform medium pore fluid flow; the experimental process is as follows:

[0120] Step 1, build experimental device

[0121] As shown in Figure 6The experimental device for forming the sub-polymer variable-pore sinusoidal wave wall pipe pore model is shown in the figure. The steps for building the experimental device include:

[0122] (1) Determine the light source position and light path design: adjust the position of the light source through the two-dimensional movable slide to ensure that the light is at the focal point of the first convex lens, so that the light forms parallel light after passing through the first convex lens and passes through the flow field to be observed.

[0123] (2) Prepare the schlieren plane: place the pore model to be observed between the first and second convex lenses, and the light parallel through the flow field in the model should ensure that the model surface is smooth and transparent, and does not affect the formation of light propagation and interference phenomenon.

[0124] (3) Adjust the light path and focus: according to the light path design, adjust the position and angle of the second convex lens and the high-speed camera to ensure that the parallel light can be accurately focused on the focal plane of the second convex lens and enter the high-speed camera lens, ensuring the stability of the light and the formation of clear interference fringes. Here, instead of using the conventional blade light shielding method, the camera shutter blades are used to shield part of the light.

[0125] (4) Install high-speed camera and image recording equipment: install the camera at the focal point of the second convex lens to capture the schlieren image on the plane. Carefully adjust the camera position to ensure that the light can maintain a high brightness while meeting the conditions for schlieren imaging. Connect the camera to the computer HDMI interface, and integrate the input video and image recording equipment recording the experimental site to realize real-time test recording.

[0126] (5) Experimental device calibration: after the completion of the construction, the calibration of the experimental device is carried out, including the adjustment of the light source intensity by the light adjuster, the accurate calibration of the light path and the calibration of the camera focal length, to ensure the clarity, accuracy and reliability of the imaging.

[0127] The matters needing attention for this step include:

[0128] The selection and stability of the light source have a significant impact on the experimental results. A high-brightness, coherent light source should be selected, and the stability of the light source should be ensured to avoid errors caused by fluctuations in light intensity.

[0129] The selection of the pore model should consider the transparency and flatness of the light propagation to avoid surface concave-convex or other factors affecting the interference phenomenon.

[0130] When adjusting the light path and focusing, careful operation should be performed to maintain the stability and accuracy of the optical elements, and avoid vibration or displacement leading to inaccurate experimental results.

[0131] The camera parameters should be adjusted according to the experimental requirements, including focal length and frame rate, to obtain clear schlieren images.

[0132] Calibration of the experimental device is an important step to ensure the accuracy of the experimental results. Detailed calibration and testing should be performed to avoid the influence of systematic errors.

[0133] Step 2, establish the sinusoidal wave wall pipe pore model of variable aperture structure;

[0134] Step 21, determine the model size and geometry;

[0135] According to the real pore structure observed in the rock sample picture, the relative size and geometry of the pore model are formed.

[0136] Step 22, determine the pore structure parameters:

[0137] Pore structure parameters can be obtained through actual reservoir data, microscopic observation of rock samples, or other measurement methods. For real pore structures smaller than the absolute geometric size of the model, dimensionless parameters can be used to describe fluid flow phenomena at different scales.

[0138] Step 23, pore model manufacturing;

[0139] Pore model manufacturing includes material selection, manufacturing process, model installation, etc.

[0140] Since the brightness change of light passing through the fluid in the model needs to be observed, suitable materials need to be selected for pore model manufacturing. Here, transparent materials (acrylic) are used. According to the geometry and size of the pore model, laser cutting and cementation manufacturing processes are selected. During manufacturing, ensure the geometric accuracy of the pore model and minimize errors to ensure the accuracy of experimental results. During the experiment, metal screws need to be installed at the fluid inlet and outlet on both sides of the model, and silicone tubes need to be used to form the fluid inlet and outlet. The pore model is fixed on an adjustable height lifting platform, and the lifting platform height is adjusted according to the position of the light to ensure its position is stable and consistent with the propagation path of the light.

[0141] Step 3, fluid injection operation

[0142] Step 31, injection tool. The experiment selects 100ml and 200ml syringes to ensure sufficient capacity and fluid control ability. Before the experiment, ensure that the syringes are clean to avoid external contamination affecting the experimental observation results.

[0143] Step 32, injection specific steps, which are critical to form clear schlieren imaging of flow field, including the following steps:

[0144] Step 321, cold water pre-injection.

[0145] In this step, cold water is injected through one inlet to cool the porous model and keep it at a low temperature. This helps to reduce the disturbance of temperature gradient and temperature change on the observation of flow field.

[0146] Step 322, remove the bubbles in the pores.

[0147] After the injection of cold water, it is necessary to ensure that there are no bubbles in the porous model. This can be done by slowly injecting cold water to allow bubbles to float out, or by using vibration or oscillation methods to help bubbles escape. At most one of the three inlets can be connected to the atmosphere, and when the syringe is removed or other operations are performed, the suspended hose needs to be clamped with a clamp, and the clamp needs to be removed before injecting hot water to ensure that no bubbles are introduced into the full water pipe; the pipe is placed vertically, the end of the hot water injection is upwards, and the end of the cold water injection is downwards to remove the bubbles and ensure that the pipe is fully cooled and the water in the pipe is cold. A part of the bubbles will stick to the pipe wall and not be easily removed. A small amount of bubbles can be retained to observe the water flow through the movement of the bubbles.

[0148] Step 323, hot water injection.

[0149] After the injection of cold water and the removal of bubbles, hot water is injected at a certain injection rate from another inlet according to the observation requirements to obtain laminar or turbulent fluid flow state. As shown in the flow field diagram of the porous model injected with hot water from the left inlet. Figure 7 It can be seen that the flow field has obvious irregular streamlines. Figure 8 As shown in the flow field diagram of the porous model injected with hot water from the right inlet.

[0150] Injecting hot water from the right inlet, observing different steps, and obtaining different fluid spatial structures, as shown in the flow field diagram of the porous model injected with hot water from the right inlet. Figure 8 It can be seen that the flow field has obvious irregular streamlines. Figure 1 As shown in the flow field diagram of the porous model injected with hot water from the right inlet. Figure 9 Fluid passes through the first pore throat and enters the second pore, and the fluid forms a clear vortex structure in the second pore. Figure 2 As shown in the flow field diagram of the porous model injected with hot water from the right inlet. Figure 10 Fluid forms a clear vortex structure in the second pore. Figure 3 As shown in the flow field diagram of the porous model injected with hot water from the right inlet. Figure 11 As shown in the flow field diagram of the porous model injected with hot water from the right inlet, the fluid flow is obviously more turbulent, and reverse flow eddies opposite to the direction of the injected fluid appear at the top and bottom of the first pore. From Figures 7-11The changes in the flow rate and pressure of the fluid can indicate the complexity of the pore space fluid flow. Moreover, these complex structures are related to the changes in pore structure and fluid flow over time. Therefore, the pore flow structure is a non-stationary process that depends on the characteristics of the pore structure and the state of fluid flow.

[0151] In this step 32, the fluid supply device and the fluid discharge device are also required.

[0152] Temperature control is crucial for the success of schlieren imaging observation. It is necessary to ensure that the fluid supply device can provide stable temperature control to maintain a constant temperature difference of the fluid and adjust it according to the experimental requirements. During the fluid injection process, the pressure of the fluid needs to be controlled to ensure accurate control of the injection rate.

[0153] Fluid discharge device. According to the experimental requirements and the characteristics of fluid discharge, choose the appropriate container to ensure effective collection and discharge of fluid. After the fluid is discharged, it should be collected and properly treated.

[0154] During the entire fluid injection and control process, the following matters need to be paid attention to:

[0155] (1) Ensure the cleanliness and non-pollution of the injection device and pipeline to avoid the influence of external impurities on the experimental results.

[0156] (2) Strictly control the rate and pressure of fluid injection to maintain the accuracy and consistency of the experiment.

[0157] (3) Closely monitor the temperature change and fluid pressure during the experiment, and adjust the control parameters in time to ensure the stability and repeatability of the experiment.

[0158] (4) After the fluid is discharged, clean and dispose of the experimental equipment and fluid residues in time to keep the experimental environment clean and safe.

[0159] Step 4, record the schlieren image

[0160] Step 41, high-speed camera preparation:

[0161] Adjust the settings of the high-speed camera in advance, including the adjustment of camera position and lens focal length. Ensure that the camera position is appropriate to capture the entire pore model in the center of the field of view, and adjust the lens focal length to obtain the appropriate image magnification ratio. Also, connect the computer video signal to ensure that the real-time recorded video can be directly transmitted to the computer for saving and subsequent analysis. In addition, in order to avoid the influence of manual operation vibration, connect the shutter control line to make the camera shutter can be controlled by electrical signal, ensure the stability of image recording.

[0162] Step 42, synchronous recording of flow field video:

[0163] Before starting the fluid injection, coordinate the actions of the fluid injection operator and the camera operator. Ensure both are ready and simultaneously start the fluid injection and the video recording of the camera. Be careful when controlling the flow field injection time, ensuring that the recording time of the high-speed camera does not exceed the specified length to avoid losing important video data.

[0164] Step 43, stop video recording and end fluid injection:

[0165] When the experiment needs to end, stop the video recording of the high-speed camera and stop the injection of the fluid. Pay attention to ensure safety and stability during the experiment.

[0166] Step 44, observation and verification of video data:

[0167] After the experiment ends, observe and verify whether the recorded video data is correct, ensuring that the flow field information in the video is clear and visible, without missing key frames or data.

[0168] Step 45, clean up and remove fluid residues, and wipe the pore model to prepare for the next experiment.

[0169] Through these steps and precautions, the accuracy and reliability of the schlieren imaging recording can be ensured, providing reliable video data for subsequent data analysis and interpretation of experimental results.

[0170] Step 5, data processing and analysis

[0171] Step 51, data export and backup:

[0172] Export the video data recorded by the schlieren imaging from the camera or storage medium to the computer for subsequent processing and analysis. Ensure the integrity and availability of the data. After exporting, make a backup to prevent data loss or damage.

[0173] Step 52, video frame extraction:

[0174] Use MATLAB system to extract frame images with obvious flow field characteristics from video data, select those key frames that can demonstrate the structure of the flow field for further analysis.

[0175] Step 53, image correction and enhancement:

[0176] Correct and enhance the extracted frame images to optimize image quality and clarity. Use image processing software such as Matlab to adjust brightness, contrast, sharpness, etc. to improve the visualization effect of the images.

[0177] Step 54, flow field analysis:

[0178] Using Matlab image processing and analysis tools, based on the light and dark distribution data of the schlieren experiment pictures, the image flow field analysis is carried out. By applying computer vision techniques such as optical flow and image correlation method, the motion and changes of fluid flow are tracked. The flow rate, vortex structure, streamline trajectory and other flow field characteristic parameters can be calculated.

[0179] Step 55, data visualization:

[0180] Using Matlab data visualization tools, the analyzed flow field data is visualized. The flow field vector diagram is generated to intuitively show the flow pattern and characteristics.

[0181] Step 56, data interpretation and result analysis:

[0182] Combined with the experimental setting and the theoretical background of porous fluid flow, the obtained flow field data is interpreted and analyzed. It can be compared with the theoretical model to verify the accuracy of the experimental observation results, and the key physical parameters and conclusions can be extracted. Through the processing and analysis of data, the laws and characteristics of porous fluid flow can be revealed, which provides quantitative results and explanations for understanding the fluid behavior of porous media, and further provides strong support for reservoir seismic exploration and oil and gas flow prediction.

[0183] The device of the experiment constituted in this example adopts the visualization experimental measurement method of the sinusoidal wall pipe pore model flow field, combined with the schlieren imaging technology, directly observes the changes of the pore fluid flow field. Not only the key information such as the velocity distribution and vortex structure of the fluid is captured in real time, but also the quantitative information of the pore structure parameters such as pore size and pore throat ratio is extracted through the observation and analysis of the flow field. The experimental measurement method realized provides a new perspective and means for reservoir seismic exploration and porous fluid research.

[0184] Those of ordinary skill in the art will realize and understand that all or some of the steps in the methods disclosed above and the functional modules / units in the systems and devices can be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementation, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component can have multiple functions, or one function or step can be performed by several physical components in cooperation. Some or all of the components can be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on computer-readable media, which can include computer storage media (or non-transitory media) and communication media (or transitory media). As is well known to those of ordinary skill in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Furthermore, it is common and well understood by those of ordinary skill in the art that communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and can include any information delivery media.

Claims

1. An experimental device for visualizing fluid flow in a pore of a medium, characterized in that, the device comprises a schlieren imaging module, an image recording module and an image processing module; the schlieren imaging module comprises a light source, a first convex lens, a second convex lens and a pore flow field model; wherein: the light source is arranged on one side of the first convex lens, and the pore flow field model is arranged on the other side of the first convex lens, and the light passes through the pore flow field model to form interference fringes after passing through the first convex lens; the pore flow field model is arranged between the first convex lens and the second convex lens, and is used to simulate the velocity distribution and vortex structure of the fluid in the pore medium; the image recording module is arranged at the output end of the schlieren imaging module, and is used to collect and record the interference fringe images formed by the schlieren imaging module, so as to analyze and display the fluid flow in the pore of the medium by using the image processing module.

2. The experimental setup for visualization of fluid flow in pores in a medium according to claim 1, characterized in that, Determination of the position of the light source: The light source is arranged at the focal point of the first convex lens.

3. The experimental device for visualizing fluid flow in a pore of a medium according to claim 1, characterized in that, Determination of the position of the second convex lens: The parallel light formed by the light passing through the first convex lens is focused on the focal plane of the second convex lens after passing through the pore flow field model.

4. The experimental set-up for visualization of fluid flow in pores in a medium according to claim 1, characterized in that, The image recording module is a camera; The camera is arranged at the focal point of the second convex lens, and is used to capture the interference fringe images on the schlieren plane.

5. The experimental device for visualizing fluid flow in a pore of a medium according to claim 1, characterized in that, The pore flow field model is a variable-pore-structure sinusoidal wall pipe pore model; The size and geometry of the variable-pore-structure sinusoidal wall pipe pore model are determined according to the real pore structure parameters of the rock sample; Wherein, the pore structure parameters include: pore average radius size, pore wall fluctuation amplitude, pore size transformation period characteristic length along the axial direction.

6. The experimental device for visualizing fluid flow in a pore of a medium according to claim 5, characterized in that, The wall surface of the variable-pore-structure sinusoidal wall pipe pore model satisfies the following conditions: In the above equation, R i (z) represents the corresponding real pore radius at the axial coordinate z, represents the average pore radius size, A represents the fluctuation amplitude of the varying pore wall surface, represents the fluctuation period in the axial direction, z represents the axial coordinate of the pore centerline, and z0 represents the initial coordinate of the axial reference point.

7. An experimental method for visualizing the flow of pore fluids in a medium, characterized in that, The method comprises: Building the experimental device for visualizing fluid flow in a pore of a medium, and calibrating the experimental device; Injecting fluid into the pore flow field model in the experimental device, and collecting and recording the interference fringe images formed during the fluid flow process; Analyzing the fluid flow in the pore of the medium according to the recorded image data, generating a flow field vector diagram and displaying it.

8. The experimental method of pore fluid flow visualization in a medium according to claim 7, wherein, The building of the experimental device for visualizing fluid flow in a pore of a medium, and the calibration of the experimental device, comprises: After the pore flow field model to be observed is arranged between the first convex lens and the second convex lens, the position of the light source is adjusted to be at the focal point of the first convex lens; The parallel light formed by the light passing through the first convex lens is focused on the focal plane of the second convex lens after passing through the pore flow field model to be observed; The image recording module is arranged at the focal point of the second convex lens and connected with the image processing device.

9. The experimental method of pore fluid flow visualization in a medium according to claim 7, wherein, The method comprises the following steps: injecting fluid into the pore flow field model in the experimental device, and collecting and recording the interference fringe image formed during the fluid flow process, including: injecting cold water into the first inlet of the pore flow field model; after the pore flow field model is cooled, removing the bubbles in the pore flow field model; 10. The experimental method of pore fluid flow visualization in a medium according to claim 7, wherein, injecting hot water through the second inlet of the pore flow field model at a preset injection rate to simulate laminar flow and turbulent flow. The method comprises the following steps: extracting feature frame images with flow field characteristics from the recorded image data; correcting and enhancing the feature frame images; calculating the processed feature frame images to obtain flow field characteristic parameters; generating a flow field vector diagram according to the flow field characteristic parameters, and displaying the vector diagram.

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