A method for measuring matrix content in nodular limestone

Abstract

This invention provides a method for measuring the matrix content in nodular limestone. It involves obtaining a core sample from a nodular limestone stratum at a specific depth in a single well. By measuring the area ratio of the matrix in the roll scan image of the core sample and the area ratio in the corresponding static electro-optical imaging image from the same location in the well, the difference between these two area ratios reaches a designed standard value. An empirical threshold for the static electro-optical imaging image is then obtained, and the matrix content in the nodular limestone is determined using this empirical threshold. The area ratio is primarily determined by adjusting the color threshold to identify the pixel values ​​of the matrix and the overall image. The matrix area ratio in the image is then calculated using these pixel values. This method eliminates the need for separate descriptions of core samples from each nodular limestone stratum at each depth in each well. Continuous data can be obtained and a quantitative description generated in one go using the empirical threshold. The method is simple to operate, highly efficient, and cost-effective.

Description

Technical Field

[0001] This invention relates to the field of nodular limestone exploration technology, and specifically designs a method for measuring the matrix content in nodular limestone. Background Technology

[0002] Nodular limestone is a type of limestone characterized by its nodular morphology and similar occurrence. It is generally composed of "nodules" and a "matrix." The "nodules" are primarily composed of grayish-white limestone. The matrix, containing organic matter, possesses significant potential for oil and gas exploration and development. Nodular limestone is widely deposited in Chinese strata, particularly in the southern Sichuan Basin, especially at the base of the Maokou Formation in the Permian system.

[0003] In existing technologies, the exploration of matrix content in nodular limestone mainly involves obtaining core samples from different depths of nodular limestone formations in a single well and performing macroscopic descriptions of these core samples to make a rough judgment on the matrix content. This method requires obtaining each core sample, which is cumbersome, inefficient, time-consuming, and incurs high time and labor costs. Furthermore, it only provides a rough assessment, with discontinuous data and no quantitative description. In particular, matrix and non-matrix components are often co-existing, and their proportions vary significantly across different strata and regions. Sometimes, it is impossible to effectively distinguish between matrix and non-matrix components in nodular limestone. Without core samples, it is temporarily impossible to quantitatively evaluate nodular limestone using downhole techniques. Therefore, using existing methods to determine the matrix distribution in nodular limestone results in low accuracy and efficiency. Summary of the Invention

[0004] The purpose of this invention is to address the problems of cumbersome operation, long time consumption, high cost, discontinuous data that cannot be quantitatively described, low accuracy and low efficiency in the existing process of surveying matrix content in nodular limestone. This invention provides a method for measuring matrix content in nodular limestone. This method can quantitatively obtain matrix content data, and it is simple to operate, efficient, time-saving, and accurate, and has high promotional value.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for measuring the matrix content in nodular limestone includes the following steps:

[0007] Step 1: Obtain the core sample of the first nodular limestone development section in a single well, and perform a rolling scan on the core sample to obtain a rolling scan image;

[0008] Step 2: Select several darker areas from the rolling scan image in Step 1, extract the core samples corresponding to the darker areas, and then collect data from the core samples.

[0009] Step 3: Use image processing software to process the sweeping image obtained in Step 1 to obtain the first image, and obtain the upper chromaticity threshold A1, lower chromaticity threshold A2 and pixel value L1 of the core sample in the first image corresponding to the data acquisition value that meets the matrix requirements. At the same time, record the total pixel value T1 of the first image, and use the pixel value to calculate the area ratio S1 of the matrix in the black and white sweeping image.

[0010] Step 4: Obtain the single-well electrical imaging static image from Step 1; perform corresponding correction on the core entity position between the black-and-white rolling scan image of the core entity in Step 1 and the single-well electrical imaging static image, and extract the image area of ​​the black-and-white rolling scan image at the corresponding position in the single-well electrical imaging static image to obtain the first electrical imaging static image; adjust the chromaticity display area of ​​the first electrical imaging static image so that the first electrical imaging static image displays the outline of the matrix at the corresponding position in the black-and-white rolling scan image; then, perform image processing on the first electrical imaging static image using the same method as in Step 3, obtain the upper chromaticity threshold B1, lower chromaticity threshold B2, and pixel value L2 corresponding to the matrix area in the processed first electrical imaging static image, and record the total pixel value T2 of the first electrical imaging static image, and calculate the area ratio S2 of the matrix in the first electrical imaging static image using the pixel value.

[0011] Step 5: Compare the difference between S2 and S1. If the difference reaches the design standard value, record B1 and B2 as the empirical threshold. If the difference does not reach the design standard value, return to step 4 to adjust the size of B1 and B2 and recalculate S2 until the difference between S2 and S1 reaches the design standard value. Then, use the obtained empirical threshold to obtain the matrix content in the nodular limestone.

[0012] The method for measuring matrix content in nodular limestone provided by this invention first obtains a core sample from a specific depth of nodular limestone development in a single well. The method then measures the area ratio of the matrix in the roll scan image of the core sample and the area ratio in the corresponding static electrical imaging image from the same location within the well. Once the difference between these two area ratios reaches a designed standard value, an empirical threshold for the static electrical imaging image is obtained. This empirical threshold is then used to determine the matrix content in the nodular limestone. Specifically, the area ratio is determined by adjusting the color threshold to identify the pixel values ​​of the matrix and the overall image, and the matrix area ratio in the image is calculated using these pixel values. Furthermore, the matrix is ​​determined using a method for acquiring core sample data. The method provided by this invention can obtain the matrix content distribution in nodular limestone using empirical thresholds, eliminating the need for separate descriptions of core samples from each depth segment of nodular limestone in each well. Continuous data can be obtained and quantitatively described at once using empirical thresholds, resulting in a simple, efficient, cost-effective, and time-saving method. By using precise sample data to determine the matrix extent and correcting for area proportions using core sample roll scans and single-well electro-optical imaging static maps, the method ensures high accuracy and further accelerates the evaluation of the oil and gas development potential of nodular limestone.

[0013] Furthermore, in step 1, the core sample is placed into a tumbling machine for tumbling processing.

[0014] Furthermore, in step 2, the darker area refers to the gray rock core, which is represented in RGB hexadecimal between #929292 and #000000.

[0015] Furthermore, in step 2, data collection for several core samples refers to collecting test data on organic carbon and porosity for several core samples.

[0016] Furthermore, in step 3, the data acquisition values ​​meeting the matrix requirements mean that the organic carbon content is not less than 1% and the porosity data is not less than 1.5%.

[0017] Furthermore, in step 3, the image processing software is ImageJ software, the first image is an 8-bit image, and the chromaticity threshold is adjusted using the adjust mode.

[0018] Furthermore, in step 3, the specific method for calculating the area ratio S1 of the matrix in the black and white scrolling image using pixel values ​​is as follows: Substitute the pixel value L1 and the total pixel value T1 into formula I to obtain S1; where formula I is: Matrix area ratio (S) = Matrix pixel value (L) / Total pixel value of the image (T). Specifically, substitute L1 into L in formula I and substitute T1 into T in the formula to calculate S1.

[0019] Furthermore, in step 4, obtaining the static electrical imaging image of a single well in step 1 means obtaining the static electrical imaging image of the entire single well in step 1, or obtaining the static electrical imaging image of the corresponding nodular limestone development section in the single well in step 1.

[0020] Furthermore, in step 4, adjusting the chromaticity display area of ​​the first electro-optical imaging static image involves setting the Heat value of the first electro-optical imaging static image to 200-1000. Preferably, in step 4, adjusting the chromaticity display area of ​​the first electro-optical imaging static image involves setting the Heat value of the first electro-optical imaging static image to 500-1000.

[0021] Furthermore, in step 4, the specific method for calculating the area ratio S2 of the matrix in the first electro-imaging static image using pixel values ​​is as follows: Substitute the pixel value L2 and the total pixel value T2 into formula I to obtain S2; where formula I is: Matrix area ratio (S) = Matrix pixel value (L) / Total pixel value of the image (T). Specifically, substitute L2 into L in formula I and T2 into T in the formula to calculate S2.

[0022] Further, in step 5, the design standard value refers to the percentage of the absolute value of S1 and S2 relative to the value of S1 being ≤10%. Preferably, in step 5, the design standard value refers to the percentage of the absolute value of S1 and S2 relative to the value of S1 being ≤7%. More preferably, in step 5, the design standard value refers to the percentage of the absolute value of S1 and S2 relative to the value of S1 being ≤5%. More preferably, in step 5, the design standard value refers to the percentage of the absolute value of S1 and S2 relative to the value of S1 being ≤3%. More preferably, in step 5, the design standard value refers to the percentage of the absolute value of S1 and S2 relative to the value of S1 being ≤1%. More preferably, in step 5, the design standard value refers to the percentage of the absolute value of S1 and S2 relative to the value of S1 being ≤0.5%.

[0023] Furthermore, in step 5, obtaining the matrix content in the nodular limestone using the obtained empirical threshold refers to obtaining the matrix area ratio of other nodular limestone development segments at different depths in the single well mentioned in step 1, thereby obtaining the matrix content distribution in the nodular limestone development segments at different depths in the single well; or it refers to obtaining the matrix area ratio of a certain depth in a nodular limestone development segment in other single wells in the same stratum environment area as the single well in step 1; or it also refers to obtaining the matrix area ratio of different depths in nodular limestone development segments in other single wells in the same stratum environment area as the single well in step 1.

[0024] Further, the specific operation for obtaining the matrix area ratio of other nodular limestone development sections at different depths in the single well mentioned in step 1 is as follows: Obtain the second electrical imaging static image of the second nodular limestone development section at different depths in the single well mentioned in step 1. Process the second electrical imaging static image using the same image processing software as in step 3, set the upper chromaticity threshold to B1 and the lower chromaticity threshold to B2, and obtain the matrix pixel value Lm and the total pixel value Tm of the second electrical imaging static image. Calculate the matrix area ratio Sm in the second electrical imaging static image using the pixel value, which is the matrix area ratio in the second nodular limestone development section of the single well. Furthermore, using the same method as obtaining the matrix area ratio of other nodular limestone development sections at different depths in the single well mentioned in step 1, obtain the matrix area ratio in a nodular limestone development section at a certain depth in other single wells in the same stratum environment area as the single well in step 1; or obtain the matrix area ratio in nodular limestone development sections at different depths in other single wells in the same stratum environment area as the single well in step 1.

[0025] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0026] The method for measuring matrix content in nodular limestone provided by this invention first obtains a core sample from a specific depth of nodular limestone development in a single well. The method then measures the area ratio of the matrix in the roll scan image of the core sample and the area ratio in the corresponding static electrical imaging image from the same location within the well. Once the difference between these two area ratios reaches a designed standard value, an empirical threshold for the static electrical imaging image is obtained. This empirical threshold is then used to determine the matrix content in the nodular limestone. Specifically, the area ratio is determined by adjusting the color threshold to identify the pixel values ​​of the matrix and the overall image, and the matrix area ratio in the image is calculated using these pixel values. Furthermore, the matrix is ​​determined using a method for acquiring core sample data. The method provided by this invention can obtain the matrix content distribution in nodular limestone using empirical thresholds, eliminating the need for separate descriptions of core samples from each depth segment of nodular limestone in each well. Continuous data can be obtained and quantitatively described at once using empirical thresholds, resulting in a simple, efficient, cost-effective, and time-saving method. By using precise sample data to determine the matrix extent and correcting for area proportions using core sample roll scans and single-well electro-optical imaging static maps, the method ensures high accuracy and further accelerates the evaluation of the oil and gas development potential of nodular limestone. Attached Figure Description

[0027] Figure 1 This is a core photograph of nodular limestone at a certain depth in Well A in Example 1.

[0028] Figure 2 yes Figure 1 The image shown is a swept-sweep photograph of nodular limestone at a certain depth in Well A.

[0029] Figure 3 yes Figure 1 Static electro-optical imaging image of a single well in the sampling section.

[0030] Figure 4 It is a magnified electronic imaging. Figure 3 The low-resistance bands form a dark-light-dark spatial diagram.

[0031] Figure 5 This is a schematic diagram of a core photograph of nodular limestone at a certain depth in Well A in Example 1.

[0032] Figure 6 This is the sixth roll scan image (number 1) of a certain depth section of well A processed by Image J software in Example 1.

[0033] Figure 7 This is the sixth roll scan image (number 2) of a certain depth section of well A processed by Image J software in Example 1.

[0034] Figure 8 This is the sixth roll scan image (number 3) of a certain depth section of well A processed by Image J software in Example 1.

[0035] Figure 9 This is the sixth sweep image (number 4) of a certain depth section of well A processed by Image J software in Example 1.

[0036] Figure 10 This is the sixth roll scan image (No. 5) of a certain depth section of well A processed by Image J software in Example 1.

[0037] Figure 11 This is the sixth electrical imaging image of a certain depth section of well A processed by Image J software in Example 1.

[0038] Figure 12 The image shown is the eighth electron imaging image of a certain depth section of well A, processed by Image J software in Example 1.

[0039] Figure 13 The image shown is from block 66-71 of the sixth cycle of the image processing in Example 1 using Image J software.

[0040] Figure 14 The image shown is from the sixth sweep of the 72nd-77th blocks of well A, processed by Image J software in Example 1.

[0041] Figure 15 The image shown is from the sixth sweep of the 78th-85th blocks of well A, processed by Image J software in Example 1.

[0042] Figure 16This is a schematic diagram of the steps of the method for measuring the matrix content in nodular limestone according to the present invention. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings.

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Example 1

[0046] The data used in the technical solution of this invention comes from the core sample of nodular limestone from Well A in a certain area of ​​southern Sichuan and the downhole logging data of the well.

[0047] A method for measuring the matrix content in nodular limestone, such as Figure 16 As shown, core samples at a certain depth were obtained on-site through a core sampling process. Figure 1 As shown, each sample was photographed using a rolling scan instrument. Specifically, the rolling scan of each sample was performed under uniform, stable lighting conditions that accurately reflected the characteristics of the rock. The resulting photographs are shown below. Figure 2 As shown.

[0048] After the rolling scan is completed, several darker areas are selected from the black and white rolling scan image, and core samples corresponding to these darker areas are extracted. Then, data are collected from these core samples. Specifically, samples are taken for porosity and organic carbon determination experiments; core samples with organic carbon content of not less than 1% and porosity of not less than 1.5% are selected.

[0049] The electrical imaging data of the well was acquired and processed using Techlog software to obtain static electrical imaging images, such as... Figure 3 As shown.

[0050] By combining well logging curves, well logging characteristics, and core images, the core images are repositioned to ensure a good correspondence between the core images and the electrical imaging images.

[0051] Figure 4 After magnification, the low-resistivity bands in the electrical imaging form a dark-light-dark space. In the magnified core photographs, from the bottom of core 8-73 to the top of core 8-78, the color gradually fades. Therefore, from core 8-69 to core 8-85, the color matches the electrical imaging response, forming a black-white-black combination. In terms of thickness, the electrical imaging (… Figure 5The three regions are 2.1m thick, with a well depth of 2856.3-2858.4m. The core thickness is 2.17m, with a well depth of 2855.99-2858.16m, and the thickness is consistent. Further analysis shows that the uppermost dark region, as indicated by electrical imaging, has a depth of 2856.32-2856.9m and a thickness of 0.6m. From the core image, the upper dark region is also 0.6m thick. Therefore, the electrical imaging depth of 2856.4m corresponds to core blocks 8-69, and the core depth should be shifted downwards by 1.02m.

[0052] By observing the core images, and targeting the development of nodular limestone, the color display range of the electro-optic static images was adjusted to allow the electro-optic static images to better capture the details of the nodular limestone and correspond as closely as possible to the core images.

[0053] The Heat value of the static image in this well was set to 200-1000, which can better reflect the details of the nodular limestone.

[0054] The images obtained in steps 2 and 4 were converted to grayscale using ImageJ software and converted to 8-bit images. The color threshold of the software was then adjusted using the adjust mode until the software pixels covered the matrix position. The threshold range was recorded. The upper and lower thresholds of the core were set to A1 and A2, respectively. The number of matrix pixels L1 and the total number of image pixels T1 were recorded. The upper and lower thresholds of the electro-imaging images were set to B1 and B2, respectively. The number of matrix pixels Ly and L2 were recorded. The total number of image pixels T2 was recorded.

[0055] Matrix area ratio (S) = Matrix pixels (L) / Total number of pixels in the image (T)

[0056] Record the matrix area ratio S1 of the core and the matrix area ratio S2 of the electrical imaging image.

[0057] Well A selected the sixth run of the nodular limestone development section, totaling 5 roll scan images, and performed grayscale conversion on each as follows: Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown, adjust the threshold until the red pixels in the software can accurately cover the matrix. Record the threshold as 30-60, the matrix pixels as 8,715,393, the total pixels as 18,137,154, and the matrix ratio as 48.05%.

[0058] Using the same method, the matrix pixel values, total pixel values, and matrix area ratio of other core images from the sixth pass were calculated and recorded in Table 1. The average matrix area ratio for a certain depth in well A during the sixth pass was calculated to be 47.38% (Table 1).

[0059] Table 1. Image J software processing of the sixth pixel data record of a certain depth section of Well A.

[0060] Sixth time Matrix pixels Total pixels Matrix ratio Figure 1 8715393 18137154 0.480527 Figure 2 14804821 19898680 0.74401 Figure 3 5586659 17097422 0.326754 Figure 4 5217272 15959160 0.326914 Figure 5 7406730 16977968 0.436255 Summary 41730875 88070384 0.473836

[0061] Continuously adjust B1 and B2 until the difference between S2 and S1 is less than 5%, and record the data of B1 and B2 at this time.

[0062] The electrophysiological imaging image corresponding to the depth segment of the core was cropped, and the left and right thresholds were adjusted using ImageJ software. The number of pixels in the covered area was calculated, and the matrix area ratio was calculated. When the threshold was adjusted to 0-137, the matrix pixel value was 18554, the total image pixel value was 93112, of which the blank line pixel value was 52266, the effective image total pixel value was 40846, and the calculated matrix area ratio was 45.42%. The error with the matrix area ratio calculation result of the core was less than 5%, proving that the feasibility was possible.

[0063] The B1 and B2 thresholds were applied to other nodular limestone sections in the same well to calculate the matrix area ratio S3.

[0064] The feasibility of thresholding was verified by selecting the eighth nodular limestone formation in Well A. In ImageJ software, the threshold for the electrical imaging images was set to 0-137 (…). Figure 12 In the core images, the threshold is set to 30-60 ( Figure 13 , Figure 14 , Figure 15 The matrix area ratio was recorded separately. Well logging showed a matrix area ratio of 58.36%, while the core sample showed a matrix area ratio of 54.65%. The error between the two matrix area ratios was less than 5%, proving the method is feasible.

[0065] Table 2. Image J software processing of the eighth pixel data record of a certain depth section of Well A.

[0066]

[0067]

[0068] The matrix area ratio Sn obtained from different layers of nodular limestone in a single well is compared with the matrix area ratio Sn at different depths to determine the depth with the highest matrix area ratio as the layer with exploration and development potential.

[0069] The method for measuring matrix content in nodular limestone provided by this invention first obtains a core sample from a specific depth of nodular limestone development in a single well. The method then measures the area ratio of the matrix in the roll scan image of the core sample and the area ratio in the corresponding static electrical imaging image from the same location within the well. Once the difference between these two area ratios reaches a designed standard value, an empirical threshold for the static electrical imaging image is obtained. This empirical threshold is then used to determine the matrix content in the nodular limestone. Specifically, the area ratio is determined by adjusting the color threshold to identify the pixel values ​​of the matrix and the overall image, and the matrix area ratio in the image is calculated using these pixel values. Furthermore, the matrix is ​​determined using a method for acquiring core sample data. The method provided by this invention can obtain the matrix content distribution in nodular limestone using empirical thresholds, eliminating the need for separate descriptions of core samples from each depth segment of nodular limestone in each well. Continuous data can be obtained and quantitatively described at once using empirical thresholds, resulting in a simple, efficient, cost-effective, and time-saving method. By using precise sample data to determine the matrix extent and correcting for area proportions using core sample roll scans and single-well electro-optical imaging static maps, the method ensures high accuracy and further accelerates the evaluation of the oil and gas development potential of nodular limestone.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring the matrix content in nodular limestone, characterized in that, Includes the following steps: Step 1: Obtain the core sample of the first nodular limestone development section in a single well, and perform a rolling scan on the core sample to obtain a rolling scan image; Step 2: Select several darker areas from the rolling scan image in Step 1, extract core samples corresponding to the darker areas, and then collect test data on organic carbon and porosity for the core samples. Step 3: Use image processing software to process the sweeping image obtained in Step 1 to obtain the first image, and obtain the upper chromaticity threshold A1, lower chromaticity threshold A2 and pixel value L1 of the core sample in the first image corresponding to the matrix requirements. At the same time, record the total pixel value T1 of the first image, and use the pixel value to calculate the area ratio S1 of the matrix in the black and white sweeping image. Among them, data collection values ​​meeting matrix requirements mean that the organic carbon content is not less than 1% and the porosity is not less than 1.5%; Step 4: Obtain the single-well electrical imaging static image from Step 1; perform corresponding correction of the core entity position between the black and white rolling scan image of the core entity in Step 1 and the single-well electrical imaging static image, and extract the image area of ​​the black and white rolling scan image at the corresponding position in the single-well electrical imaging static image to obtain the first electrical imaging static image. Adjust the chromaticity display area of ​​the first electro-optic still image, and set the Heat value of the first electro-optic still image to 200. 1000, so that the first electro-imaging static image displays the outline of the matrix at the corresponding position in the black and white rolling scan image; then, the first electro-imaging static image is processed using the same method as in step 3, and the upper chromaticity threshold B1, the lower chromaticity threshold B2 and the pixel value L2 corresponding to the matrix region in the processed first electro-imaging static image are obtained. At the same time, the total pixel value T2 of the first electro-imaging static image is recorded, and the area ratio S2 of the matrix in the first electro-imaging static image is calculated using the pixel value. Step 5: Compare the difference between S2 and S1. If the difference reaches the design standard value, record B1 and B2 as the empirical threshold. If the difference does not reach the design standard value, return to step 4 to adjust the size of B1 and B2 and recalculate S2 until the difference between S2 and S1 reaches the design standard value. Then, use the obtained empirical threshold to obtain the matrix content in the nodular limestone. Specifically, obtaining the matrix content in nodular limestone using the acquired empirical threshold refers to obtaining the matrix area ratio of other nodular limestone development sections at different depths in the single well described in step 1, thereby obtaining the matrix content distribution in nodular limestone development sections at different depths in the single well; or it refers to obtaining the matrix area ratio of a certain depth in nodular limestone development sections in other single wells in the same stratum environment area as the single well in step 1; or it also refers to obtaining the matrix area ratio of different depths in nodular limestone development sections in other single wells in the same stratum environment area as the single well in step 1.

2. The method for measuring the matrix content in nodular limestone according to claim 1, characterized in that, In step 3, the image processing software is ImageJ, and the first image is 8. For bit-type images, the chroma threshold is adjusted using the adjust mode.

3. The method for measuring the matrix content in nodular limestone according to claim 1, characterized in that, In step 3, the specific operation method for calculating the area ratio S1 of the matrix in the black and white scrolling image using pixel values ​​is as follows: Substitute the pixel value L1 and the total pixel value T1 into formula I to obtain S1; where formula I is: matrix area ratio (S) = matrix pixel value (L) / total pixel value of the photo (T).

4. The method for measuring the matrix content in nodular limestone according to claim 1, characterized in that, In step 5, the design standard value refers to the absolute difference between the S1 value and the S2 value being ≤10%.

5. The method for measuring the matrix content in nodular limestone according to claim 4, characterized in that, In step 5, the design standard value refers to the absolute difference between the S1 value and the S2 value being ≤7%.

6. According to claim 1 5. The method for measuring the matrix content in nodular limestone according to any one of the claims, characterized in that, The specific steps for obtaining the matrix area ratio of other nodular limestone development intervals at different depths in the single well mentioned in step 1 are as follows: Obtain second electrical imaging static images of the second nodular limestone development zone at different depths in the single well described in step 1. Process the second electrical imaging static images using the same image processing software as described in step 3. Set the upper chromaticity threshold to B1 and the lower chromaticity threshold to B2 to obtain the matrix pixel value Lm and the total pixel value Tm of the second electrical imaging static image. Calculate the area ratio Sm of the matrix in the second electrical imaging static image using the pixel value, which is the area ratio of the matrix in the second nodular limestone development zone of the single well.

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