A method for calculating the embedding degree of proppants based on Matlab digital image analysis technology

Abstract

The present invention discloses a method for calculating the embedding degree of proppants based on Matlab parsing digital image technology, which includes the following processes: performing a proppant embedding experiment under a target closure pressure by using a rock column and proppants wrapped with a fluorescent agent on the surface; after the proppant embedding experiment under the target closure pressure is completed, removing the proppants on the surface of the rock column, taking a photo of the embedding surface of the rock column under dark conditions to obtain an image of the embedding surface of the rock column; preprocessing the image of the embedding surface of the rock column with Matlab to obtain a binary grayscale image; using the sum function and numel function in Matlab to calculate the area and degree of proppant embedding in the rock column in the binary grayscale image. The present invention can accurately calculate the area and degree of proppant embedding on the surface of the rock column under different formation closure pressure conditions during the hydraulic fracturing process through Matlab parsing digital image technology. Its principle is reliable, the measurement method has high precision, and it can accurately represent the proppant embedding degree during the hydraulic fracturing process.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas development, and is mainly used for measuring the degree of proppant embedding in a rock column. In particular, it relates to a method for calculating the degree of proppant embedding based on Matlab-analyzed digital image technology. Background Technique

[0002] As an important measure for increasing oil and gas production in oil and gas fields, the hydraulic fracturing technology plays a significant role in the development process of various oil and gas reservoirs. Hydraulic fracturing is a process in which a large amount of proppant and fracturing fluid are pumped into the formation by a ground high-pressure pump unit during the reservoir fracturing construction, so that a large number of artificial fracture networks are formed after the reservoir is fractured, thereby increasing the permeability of the reservoir and achieving the purpose of increasing production by fracturing. However, after the fracturing operation, the fracturing fluid returns from the fractures, and the proppant remains in the fractures. Under the influence of the formation closure pressure, the proppant will inevitably interact with the rock and show a certain degree of embedding into the fracture wall surface, resulting in a decrease in the effective width of the fracture, seriously affecting the fracturing effect, and further causing a decrease in the fracture conductivity. Therefore, studying and accurately calculating the degree of proppant embedding under the target closure pressure conditions is of great significance for optimizing the design of hydraulic fracturing construction parameters and thus increasing the production of oil and gas reservoirs.

[0003] Through research on the existing technology, it is found that the currently commonly used method for representing the degree of proppant embedding is mainly to measure the depth of proppant embedding in a rock column under the target closure pressure conditions, and there is less research on calculating the area of proppant embedding in a rock column under the target closure pressure conditions. Moreover, the embedding depths of all the proppants embedded in the fractures during the fracturing process are not completely the same, so using the depth of proppant embedding in a rock column to represent the degree of proppant embedding has a certain error. Summary of the Invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a method for calculating the degree of proppant embedding based on Matlab-analyzed digital image technology. The present invention can accurately calculate the area and degree of proppant embedding on the surface of a rock column under different formation closure pressure conditions during the hydraulic fracturing process through Matlab-analyzed digital image technology. Its principle is reliable, the measurement method has high precision, and it can accurately represent the degree of proppant embedding during the hydraulic fracturing process.

[0005] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A method for calculating the degree of proppant embedding based on Matlab-analyzed digital image technology includes the following processes:

[0007] Conduct a proppant embedding experiment under the target closure pressure using a rock column and proppant wrapped with a fluorescent agent on its surface;

[0008] After the proppant embedding experiment under the target closure pressure is completed, remove the proppant on the surface of the rock column, and take a photo of the embedding surface of the rock column under dark conditions to obtain the rock column embedding surface image;

[0009] Preprocess the rock column embedding surface image with Matlab to obtain a binary grayscale image;

[0010] Use the sum function and numel function in Matlab to calculate the area and degree of proppant embedding in the rock column in the binary grayscale image.

[0011] Preferably, the rock column is made of outcrop core of the hydraulic fracturing horizon, and the surface of the rock column is smooth and flat.

[0012] Preferably, the preparation process of the proppant wrapped with a fluorescent agent includes: soaking the proppant in the fluorescent agent and stirring to make all the proppants completely wrapped with the fluorescent agent, and then taking out the proppant and drying it.

[0013] Preferably, the amount of proppant is calculated according to the proppant placement concentration required by the experiment, and the calculation process is as follows:

[0014] M = AC

[0015] Where M is the mass of the proppant, in grams; A is the true area of the upper surface of the rock column; C is the placement concentration, in kilograms per square meter.

[0016] Preferably, the device for the proppant embedding experiment under the target closure pressure includes an embedding chamber and a hydraulic press platform. The embedding chamber includes a piston and an embedding chamber main body. The embedding chamber main body is a cylindrical cavity container with a bottom and no cover. The lower end of the piston is inserted into the inner cavity of the embedding chamber main body and is in clearance fit with the inner cavity of the embedding chamber main body. The upper end of the piston extends to the outside of the embedding chamber main body;

[0017] When using the rock column and the proppant wrapped with a fluorescent agent to conduct the proppant embedding experiment under the target closure pressure, place the rock column at the bottom of the inner cavity of the embedding chamber main body, then lay the proppant wrapped with a fluorescent agent flat on the upper surface of the rock column, and then insert the lower end of the piston into the embedding chamber main body; then place the assembled embedding chamber on the hydraulic press platform to simulate the process of proppant embedding into the formation under the condition of formation closure pressure.

[0018] Preferably, the pressure range that the hydraulic press can provide is 0 Mpa - 103 Mpa.

[0019] Preferably, when photographing the embedding surface of the rock pillar under dark conditions to obtain an image of the embedding surface of the rock pillar, a Canon EOS 200DII digital camera and a standard lens with a focal length of 50 mm are used to photograph the embedding surface of the rock pillar. The photo resolution is set to 3440×1440 pixels. When taking the photo, the camera lens is kept parallel to the embedding surface of the rock pillar, and the photo is saved in JPEG format.

[0020] Preferably, the process of preprocessing the image of the embedding surface of the rock pillar with Matlab to obtain a binary grayscale image includes:

[0021] Read the image information of the image of the embedding surface of the rock pillar through the imread function in Matlab;

[0022] Use the Laplacian operator to sharpen and enhance the image of the embedding surface of the rock pillar to enhance the proppant embedding area in the image;

[0023] Use the rgb2gray function to convert the sharpened and enhanced image of the embedding surface of the rock pillar into a grayscale image;

[0024] Use the median filtering medfilt2 function to remove the noise points in the converted grayscale image;

[0025] Use the im2bw function to perform binary processing on the grayscale image after removing noise points to obtain a binary grayscale image; in the binary grayscale image, the pixel value of the proppant embedding area is 1, showing white, and the pixel value of the area of the embedding surface of the rock pillar not embedded with proppant is 0, showing black.

[0026] Preferably, the process of using the sum function and numel function in Matlab to calculate the area and degree of proppant embedded in the rock pillar in the binary grayscale image includes:

[0027] Use the Gaussian-Laplacian operator to perform edge detection on the proppant embedding area in the preprocessed binary grayscale image, and then use the sum function and numel function in Matlab to calculate the number of pixel points in the proppant embedding area, and obtain the area and degree of proppant embedded in the rock pillar according to the number of pixel points in the proppant embedding area.

[0028] Preferably, the calculation method of the area of proppant embedded in the rock pillar is as follows:

[0029] S = A×(n1÷n)

[0030] where S is the proppant embedding area, with the unit of cm 2 ; A is the true area of the upper surface of the rock pillar; n1 is the number of pixel points in the proppant embedding area; n is the total number of pixel points in the image of the upper surface of the rock pillar;

[0031] The degree of proppant embedding in the rock column is the ratio of the area where the proppant is embedded in the rock column to the true area of the upper surface of the rock column.

[0032] The present invention has the following beneficial effects:

[0033] In the method for calculating the proppant embedding degree based on the Matlab digital image analysis technology of the present invention, when using a rock column and proppants wrapped with a fluorescent agent to conduct an experiment on proppant embedding under the target closing pressure, the proppants wrapped with the fluorescent agent will inevitably interact with the surface of the underlying rock column under the target closing pressure and show a certain degree of embedding on the upper surface of the rock column. By using the Matlab digital image analysis technology, the embedded surface image of the rock column can be processed into a white proppant embedding area and a black area not embedded by the proppant. Thus, by calculating the number of pixel points in the white area and the black area, the area and degree of the proppant embedded in the rock column can be obtained, realizing the intelligent measurement of the proppant embedding degree. Therefore, the present invention improves the measurement accuracy, overcomes the defects of the existing technology for measuring the proppant embedding degree, avoids the errors caused by the insufficient accuracy of the measuring device, and the results are more objective and accurate. Description of the Drawings

[0034] Figure 1 It is a schematic flow chart of the method for calculating the proppant embedding degree based on the Matlab digital image analysis technology provided by the present invention;

[0035] Figure 2 It is a schematic longitudinal sectional view of the embedding chamber assembled according to the present invention;

[0036] Figure 3 It is a binary image of the embedded surface of the rock column after Matlab preprocessing in Embodiment 1 of the present invention;

[0037] Figure 4 It is a binary image of the embedded surface of the rock column after Matlab preprocessing in Embodiment 2 of the present invention.

[0038] Among them, 1 is a piston, 2 is the main body of the embedding chamber, 3 is the proppant, and 4 is the rock column Detailed Embodiment

[0039] The following will further illustrate the present invention with reference to the drawings and embodiments.

[0040] Refer to Figure 1 , the method for calculating the proppant embedding degree based on the Matlab digital image analysis technology of the present invention includes the following steps:

[0041] S1. Use a wire cutting machine to make a rock column from the outcrop core of the hydraulic fracturing layer. The specific process is as follows: Process the rock sample into a rock column with a smooth and flat surface according to the size of the hydraulic press embedding chamber. Refer to Figure 2, the embedding chamber includes an embedding chamber body 2 and a piston 1. The embedding chamber body 2 is a cylindrical cavity container with a bottom but no lid. The lower end of the piston 1 extends into the inner cavity of the embedding chamber body 2 and is in clearance fit with the inner cavity of the embedding chamber body 2. The cross-sectional area of the cavity in the inner cavity of the embedding chamber body 2 and the diameter of the piston 1 are both 50 mm. The height of the piston 1 is 88 mm, and the height of the cavity container is 76 mm. The size of the prepared rock column is: diameter 50 mm, height 10 mm.

[0042] S2. Immerse the proppant in the fluorescent agent and stir it until all the proppants are completely wrapped by the fluorescent agent, then take them out and dry. When performing this step, the particle size, type, and dosage of the proppant need to be selected according to the specific experimental requirements. Immerse the selected proppant in the fluorescent agent and stir to ensure that the outer surface of each proppant is completely wrapped by the fluorescent agent. The dosage of the proppant is calculated according to the proppant placement concentration required by the experiment. The calculation process is as follows:

[0043] M = AC

[0044] M—the mass of the proppant, unit: gram (g);

[0045] A—the true area of the upper surface of the rock column, take 1.963×10 -3 m 2 ;

[0046] C—the placement concentration, unit: kilogram per square meter (kg / m 2 );

[0047] S3. Assemble the rock column and proppant in the embedding chamber and conduct a proppant embedding experiment under the target closure pressure. When conducting the experiment, place the prepared rock column at the bottom of the inner cavity of the embedding chamber body 2. After spreading the proppant prepared in step S2 evenly on the upper surface of the rock column, slowly place the piston. Place the assembled embedding chamber on the hydraulic press platform to simulate the process of proppant embedding into the formation under the formation closure pressure conditions. The pressure range that the hydraulic press can provide is 0 Mpa - 103 Mpa.

[0048] S4. After the experiment, remove the proppant on the surface of the test rock column, and take a photo of the embedded surface of the rock column with a digital camera under dark conditions. When taking the photo, since the focal length of each camera is different, the image ratio of the embedded surface of the rock column taken will also be different, which will affect the design of the algorithm. Therefore, in this invention, a Canon EOS 200DII digital camera and a standard lens with a focal length of 50 mm are fixedly used to take a photo of the embedded surface of the rock column. The photo resolution is set to 3440×1440 pixels. When taking the photo, the camera lens is kept parallel to the embedded surface of the rock column, and the photo is saved in JPEG format.

[0049] S5. Preprocess the image of the embedded surface of the rock column taken by the digital camera with Matlab. The preprocessing process includes:

[0050] Read the image information obtained in step S4 through the imread function built in Matlab;

[0051] Use the Laplacian operator to sharpen and enhance the image of the rock column embedding surface, and enhance the proppant embedding area in the image;

[0052] Use the rgb2gray function to convert the image into a grayscale image;

[0053] Use the median filter medfilt2 function to remove the noise in the converted grayscale image;

[0054] Use the im2bw function to perform binary processing on the image to obtain a binary grayscale image. Finally, the pixel value of the proppant embedding area in the rock column embedding surface image is 1, which appears as white, and the pixel value of the rock column embedding surface area not embedded by the proppant is 0, which appears as black.

[0055] S6. Use the sum function and numel function in Matlab to calculate the area and degree of proppant embedded in the rock column. Specifically: Use the Gaussian-Laplacian operator to perform edge detection on the proppant embedding area in the preprocessed rock column embedding surface image, and then use the sum function and numel function in Matlab to calculate the area and degree of proppant embedded in the rock column by calculating the number of pixel points in the proppant embedding area.

[0056] Since a digital image is composed of individual pixel points, under the condition that the true area represented by each pixel point is known, the area of the target area in the image can be calculated by calculating the number of pixel points in the target area and the total number of pixel points in the image. And in the binary image of the proppant embedding surface, the pixel value of the white area is 1, representing the proppant embedding area, and the pixel value of the black area is 0, representing the area not embedded by the proppant. Therefore, calculating the proppant embedding area is to calculate the area of the white area in this binary image, which can be calculated according to the following formula:

[0057] S = A × (n1 ÷ n)

[0058] S - Proppant embedding area, unit is (cm 2 );

[0059] A - True area of the upper surface of the rock column, which is 19.63 cm 2 ;

[0060] n1 - Number of pixel points in the proppant embedding area;

[0061] n - Total number of pixel points in the image of the upper surface of the rock column.

[0062] Example 1

[0063] The method for calculating the embedding degree of proppants based on Matlab parsing digital image technology in this embodiment includes the following steps:

[0064] (1) Select 1 outcrop core of the hydraulic fracturing horizon, and use a wire cutting machine to make this core into a rock column with a diameter of 50 mm and a height of 10 mm.

[0065] (2) Select 40-60 mesh ceramic proppants, soak them in a fluorescent agent and stir, take them out and dry them after the outer surfaces of all proppants are completely wrapped by the fluorescent agent for subsequent experiments.

[0066] (3) Place the rock column prepared in step (1) into the cavity of the embedding chamber, evenly lay 5 kg / m 2 The proppants processed in step (2) on the upper surface of the rock column. After laying the proppants flat, slowly place the piston, so that the proppants are evenly laid between the rock column and the piston. Place the assembled embedding chamber on the hydraulic press platform, and then turn on the hydraulic press to apply a closing pressure of 5 Mpa to the embedding chamber and keep it for 30 min.

[0067] (4) After the experiment, unload the closing pressure, take out the piston and the rock column of the embedding chamber in turn, remove the proppants on the surface of the rock column, and then take a photo of the embedded surface of the rock column with a Canon EOS 200DII digital camera and a standard lens with a focal length of 50 mm under dark conditions. Set the photo resolution to 3440×1440 pixels, keep the camera lens parallel to the embedded surface of the rock column during taking pictures, and save the photo in JPEG format.

[0068] (5) Preprocess the image of the embedded surface of the rock column taken by the Canon EOS 200DII digital camera. Use the imread function built in Matlab to read the image of the embedded surface of the rock column; use the Laplace operator to sharpen and enhance the image of the embedded surface of the rock column to enhance the details in the image; use the rgb2gray function to grayscale the image read by the imread function; use the median filtering medfilt2 function to remove the noise in the converted grayscale image; use the im2bw function to binarize the image to obtain a binarized grayscale image, that is, the pixel value of the proppant embedding area in the image of the embedded surface of the rock column is 1 and appears white, and the pixel value of the area of the embedded surface of the rock column not embedded by the proppant is 0 and appears black. The obtained image is as Figure 3 shown.

[0069] (6) Edge detection was performed on the proppant embedding area in the preprocessed pillar embedding surface image using the Gaussian-Laplace operator. Then, the sum function and numel function in Matlab were used to obtain the number of pixels n1 in the proppant embedding area as 2,625, and the total number of pixels n in the upper surface image of the rock pillar was 62,093. Thus, the sand-laying concentration was obtained as 5 kg / m 2 The embedding area of 40-60 mesh ceramsite proppant with a closing pressure of 5 Mpa on the upper surface of this rock pillar was 0.83 cm 2 , and the calculated embedding degree was 4.23%.

[0070] Example 2

[0071] The method for calculating the proppant embedding degree based on Matlab's digital image analysis technology in this example includes the following steps:

[0072] (1) One outcrop core of the hydraulic fracturing horizon was selected, and this core was made into a rock pillar with a diameter of 50 mm and a height of 10 mm using a wire cutting machine.

[0073] (2) 20-40 mesh ceramsite proppant was selected and soaked and stirred in a fluorescent agent. After all the proppant outer surfaces were completely wrapped by the fluorescent agent, it was taken out and dried for subsequent experiments.

[0074] (3) The rock pillar prepared in step (1) was placed in the embedding chamber cavity, and 10 kg / m of the proppant processed in step (2) was evenly spread on the upper surface of the rock pillar. After the proppant was spread flat, the piston was slowly placed, so that the proppant was evenly spread between the rock pillar and the piston. The assembled embedding chamber was placed on the hydraulic press platform, and then the hydraulic press was started to apply a closing pressure of 25 Mpa to the embedding chamber and maintained for 30 min. 2 After the experiment, the closing pressure was unloaded, the piston and the rock pillar of the embedding chamber were taken out in turn, the proppant on the surface of the rock pillar was removed, and then the embedding surface of the rock pillar was photographed with a Canon EOS 200DII digital camera and a standard lens with a focal length of 50 mm under dark conditions. The photo resolution was set to 3440×1440 pixels, and the camera lens was kept parallel to the embedding surface of the rock pillar during photographing. The photo was saved in JPEG format.

[0075] (4) After the experiment, the closing pressure was unloaded, the piston and the rock pillar of the embedding chamber were taken out in turn, the proppant on the surface of the rock pillar was removed, and then the embedding surface of the rock pillar was photographed with a Canon EOS 200DII digital camera and a standard lens with a focal length of 50 mm under dark conditions. The photo resolution was set to 3440×1440 pixels, and the camera lens was kept parallel to the embedding surface of the rock pillar during photographing. The photo was saved in JPEG format.

[0076] (5) Preprocess the image of the proppant-embedded surface of the rock pillar taken by a Canon EOS 200DII digital camera. Use the imread function built in Matlab to read the image of the proppant-embedded surface of the rock pillar; use the Laplacian operator to sharpen and enhance the image of the proppant-embedded surface to enhance the detailed parts in the image; use the rgb2gray function to grayscale the image read by the imread function; use the median filter medfilt2 function to remove the noise in the transformed grayscale image; use the im2bw function to perform binary processing on the image to obtain a binary grayscale image, that is, the pixel value of the proppant-embedded area in the image of the proppant-embedded surface of the rock pillar is 1 and appears as white, and the pixel value of the area of the proppant-embedded surface of the rock pillar not embedded by the proppant is 0 and appears as black. The obtained image is as Figure 4 shown.

[0077] (6) Use the Gaussian-Laplacian operator to perform edge detection on the proppant-embedded area in the preprocessed image of the proppant-embedded surface of the rock pillar. Then use the sum function and numel function in Matlab to obtain that the number of pixel points n1 in the proppant-embedded area is 7536, and the total number of pixel points n in the image of the upper surface of the rock pillar is 63525. Thus, according to the formula S = A×(n1÷n), the embedding area of the 20-40 mesh ceramic proppant with a sand-laying concentration of 10 kg / m 2 on the upper surface of this rock pillar under a closing pressure of 25 Mpa is 2.33 cm 2 , and the calculated embedding degree is 11.86%.

Claims

1. A method for calculating the embedding degree of proppants based on Matlab digital image analysis technology, characterized in that, It includes the following processes: Conduct a proppant embedding experiment under the target closure pressure using a rock column and proppants wrapped with fluorescent agents on the surface; After the proppant embedding experiment under the target closure pressure ends, remove the proppants on the surface of the rock column, and take a photo of the embedding surface of the rock column under dark conditions to obtain an image of the embedding surface of the rock column; Preprocess the image of the embedding surface of the rock column using Matlab to obtain a binary grayscale image; Use the sum function and numel function in Matlab to calculate the area and degree of proppant embedding in the rock column in the binary grayscale image; The process of preprocessing the image of the embedding surface of the rock column using Matlab to obtain a binary grayscale image includes: Read the image information of the image of the embedding surface of the rock column through the imread function in Matlab; Use the Laplacian operator to sharpen and enhance the image of the embedding surface of the rock column to enhance the proppant embedding area in the image; Use the rgb2gray function to convert the sharpened and enhanced image of the embedding surface of the rock column into a grayscale image; Use the median filter medfilt2 function to remove the noise in the converted grayscale image; Use the im2bw function to perform binary processing on the grayscale image after removing the noise to obtain a binary grayscale image; in the binary grayscale image, the pixel value of the proppant embedding area is 1, showing white, and the pixel value of the embedding surface area of the rock column not embedded by the proppant is 0, showing black; The process of using the sum function and numel function in Matlab to calculate the area and degree of proppant embedding in the rock column in the binary grayscale image includes: Use the Gaussian-Laplacian operator to perform edge detection on the proppant embedding area in the preprocessed binary grayscale image, and then use the sum function and numel function in Matlab to calculate the number of pixels in the proppant embedding area, and obtain the area and degree of proppant embedding in the rock column according to the number of pixels in the proppant embedding area; The calculation method of the area of proppant embedding in the rock column is as follows: S = A×(n1÷n) Among them, S is the embedding area of the proppant, with the unit of cm 2 ; A is the true area of the upper surface of the rock column: n1 is the number of pixel points in the proppant embedding area; n is the total number of pixel points in the image of the upper surface of the rock column; The degree of proppant embedding in the rock column is the ratio of the area of proppant embedding in the rock column to the true area of the upper surface of the rock column.

2. The method for calculating the embedding degree of proppants based on Matlab digital image analysis technology according to claim 1, wherein The rock column is made of outcrop cores of the hydraulic fracturing horizon, and the surface of the rock column is smooth and flat.

3. A method for calculating the embedding degree of proppants based on Matlab digital image analysis technology according to claim 1, characterized in that The preparation process of the proppants wrapped with fluorescent agents on the surface includes: soaking and stirring the proppants in the fluorescent agent so that all the proppants are completely wrapped by the fluorescent agent, and then taking out the proppants and drying them.

4. A method for calculating the embedding degree of proppants based on Matlab digital image analysis technology according to claim 3, characterized in that, The amount of proppants is calculated according to the proppant placement concentration required by the experiment, and the calculation process is as follows: M = AC Where, M is the mass of the proppants, in grams; A is the true area of the upper surface of the rock column; C is the placement concentration, in kilograms per square meter.

5. A method for calculating the embedding degree of proppants based on Matlab digital image analysis technology according to claim 1, characterized in that The device for conducting the proppant embedding experiment under the target closure pressure includes an embedding chamber and a hydraulic press platform. The embedding chamber includes a piston (1) and an embedding chamber main body (2). The embedding chamber main body (2) is a cylindrical cavity container with a bottom and no cover. The lower end of the piston (1) is inserted into the inner cavity of the embedding chamber main body (2) and is in clearance fit with the inner cavity of the embedding chamber main body (2). The upper end of the piston (1) extends to the outside of the embedding chamber main body (2); When conducting the proppant embedding experiment under the target closure pressure using a rock column and proppants wrapped with fluorescent agents on the surface, place the rock column at the bottom of the inner cavity of the embedding chamber body (2), then spread the proppants wrapped with fluorescent agents on the surface evenly on the upper surface of the rock column, and then insert the lower end of the piston (1) into the embedding chamber body (2); then place the assembled embedding chamber on the hydraulic press platform to simulate the process of proppants embedding into the formation under the formation closure pressure conditions.

6. A method for calculating the embedding degree of proppants based on Matlab digital image analysis technology according to claim 5, characterized in that The pressure range that the hydraulic press can provide is 0 Mpa - 103 Mpa.

7. A method for calculating the embedding degree of proppants based on Matlab digital image analysis technology according to claim 1, characterized in that When taking a photo of the embedding surface of the rock column under dark conditions to obtain the image of the rock column embedding surface, use a Canon EOS 200DII digital camera and a standard lens with a focal length of 50 mm to take a photo of the rock column embedding surface, set the photo resolution to 3440×1440 pixels, keep the camera lens parallel to the rock column embedding surface during shooting, and save the photo in JPEG format.

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