Electric imaging crack opening degree correction method based on image crack segmentation and selection

Abstract

The invention discloses an electrical imaging crack opening degree correction method based on image crack segmentation and selection. The method comprises the following steps: processing natural gamma logging data of a crack development section and electrical imaging picture data of a crack to obtain a natural gamma characteristic value of the crack development section and an image crack opening degree; obtaining the actual fracture opening according to the actual rock core fracture picture; performing first crack correction according to the natural gamma characteristic value of the rock core of the crack development section, the software crack opening degree and the image crack opening degree; finally, a second correction formula is determined according to the actual crack opening degree and the image crack opening degree, secondary correction is conducted on the first crack correction result, the crack opening degree secondary correction method is high in correction accuracy, only 8-20 crack electric imaging pictures and actual rock core crack pictures are needed, and the correction accuracy is high. Therefore, the opening degree of a large number of cracks calculated by commercial software can be corrected.

Description

Technical Field

[0001] The invention belongs to the technical field of geological exploration, and in particular relates to an electrical imaging crack opening correction method based on image crack segmentation and selection. Background Art

[0002] In geological exploration, oil and gas exploration and development, geotechnical engineering and many other fields closely related to earth science, natural fractures are of great significance for the analysis of geological tectonic movement, the evaluation of oil and gas resource storage and seepage characteristics, the effect of hydraulic fracturing expansion and the prediction of slope stability. As a key parameter reflecting the development of fractures inside rocks, the accuracy of fracture opening directly affects the construction of geological models, the formulation of oil and gas resource development strategies and the evaluation of geotechnical engineering safety. At present, the main way to calculate fracture opening is based on electrical imaging logging, which is completed through logging processing and interpretation analysis software (such as Techlog, Ciflog, etc.). The advantage of logging processing and interpretation analysis software is that its fracture parameter calculation module can be batch operated to save time, but it also has obvious disadvantages, that is, the analysis software generally has the problem of large fracture opening calculation results. Depending on the type of formation, the error between the fracture opening calculated by the analysis software and the actual fracture opening can reach several times or even dozens of times. This significant error seriously weakens the application value of fracture opening data, so there is an urgent need for a fracture opening correction method to achieve accurate correction of the fracture opening calculated by commercial analysis software. Summary of the invention

[0003] In order to overcome the above-mentioned shortcomings, an electrical imaging fracture opening correction method based on image fracture segmentation and selection is proposed. The fracture opening secondary correction method proposed in the present invention can make a more accurate fracture opening correction. By using electrical imaging data and actual core fracture opening to connect, the accuracy of correction is improved. Only electrical imaging pictures of 8-20 fractures and actual core fracture photos are needed to correct a large number of fracture openings calculated by commercial software.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is to provide an electrical imaging fracture opening correction method based on image fracture segmentation and selection. The specific operation is as follows: S1, obtaining data: obtaining the initial fracture opening, natural gamma logging data of the fracture development section, electrical imaging pictures of the fracture, and actual core fracture photos corresponding to the depth of the electrical imaging logging pictures from the analysis software;

[0005] S2, data processing: S2.1 obtain the natural gamma ray characteristic value of the fracture development section from the natural gamma ray logging data of the fracture development section; S2.2 process the electrical imaging image of the fracture to obtain the image fracture opening;

[0006] S2.3 Obtain the actual fracture opening according to the actual core fracture photos;

[0007] S3, first correction: Classify the cracks according to the natural gamma eigenvalues ​​of the crack development segment, and perform the first crack correction based on the initial crack opening and the image crack opening, so as to improve the accuracy of the initial crack opening to be close to that of the image crack opening, and obtain the first correction result;

[0008] S4, second calibration: based on the actual crack opening and the image crack opening, the first calibration result is equated with the image crack opening to perform a second data calibration of the crack opening, and the accuracy of the initial crack opening is corrected to be the same as the actual crack opening to obtain the second calibration result.

[0009] According to the electrical imaging fracture opening correction method based on image fracture segmentation and selection described in the present invention, its further preferred technical solution is: S2.1 The specific steps are: processing the natural gamma logging data of the fracture development section, and using a single eigenvalue to represent the natural gamma value of the fracture development section.

[0010] According to the electrical imaging crack opening correction method based on image crack segmentation and selection of the present invention, a further preferred technical solution is: the natural gamma eigenvalue of the crack development section is obtained by two methods:

[0011] Steps:

[0012] a. Use the half-width method to read the natural gamma logging data of the fracture development section, with 0.1m as a section to read the natural gamma logging data.

[0013] Gamma value;

[0014] b. Calculate the natural gamma characteristic value of the fracture development section using formula (1)

[0015]

[0016] Where: GR i is the natural gamma logging data of the fracture development section, where i = 1, 2, 3, ..., n; GR eigen is the natural gamma characteristic value of the fracture development section.

[0017] The electrical imaging crack opening correction based on image crack segmentation and selection according to the present invention

[0018] The method further comprises the following preferred technical solutions: Step S2.2 comprises three steps:

[0019] a. In the electrical imaging image of the crack, only the crack area is included. Draw the R, G, and B grayscale histograms of the area. The R grayscale histogram of the area will show a multi-peak distribution. The two peaks with the lowest grayscale values ​​are plotted.

[0020] The gray value of the lowest point between the values ​​is taken as the crack gray threshold;

[0021] b. According to formula (2), the electrical imaging image of the crack is segmented to obtain the electrical imaging crack segmentation image

[0022]

[0023] Where: src is the image gray value matrix; thresh is the crack gray threshold; G Fiss Segmentation images for electrical imaging cracks;

[0024] c. Randomly select four sampling points of the crack in the electrical imaging crack segmentation image, measure the crack opening at the four sampling points, and calculate the image crack opening by formula (3):

[0025]

[0026] Where: l is the diameter of the well; H j is the crack opening of the sampling point, where j = 1, 2, 3, 4; L is the width of the electrical imaging image; H Fiss-image is the image crack opening degree; the unit in the formula is mm.

[0027] According to the electrical imaging fracture opening correction method based on image fracture segmentation and selection described in the present invention, a further preferred technical solution is: in S2.3, in order to ensure that there is a clear and accurate reference in the actual core fracture photo, the opening of the four sampling points of the fracture in the actual core fracture photo and the size of the reference image are measured, and the actual size of the reference is determined at the same time. Finally, the actual fracture opening in the core photo is calculated according to formula (4):

[0028]

[0029] Where: H photo-i is the crack photo opening, where i = 1, 2, 3, 4; L photo is the reference image size; L actual is the actual size of the reference object; H actual is the actual opening of the crack; the unit in the formula is mm.

[0030] According to the electrical imaging crack opening correction method based on image crack segmentation and selection of the present invention, a further preferred technical solution is: step S3 is specifically:

[0031] S3.1, Determination of the first correction formula:

[0032] The first correction formula is determined based on the natural gamma eigenvalue, initial fracture opening and

[0033] The image crack opening is based on the following three steps:

[0034] a. Based on the initial crack opening and the image crack opening, the opening is calculated by formula (5)

[0035] Degree ratio

[0036] H com =H Fiss-image / H Fiss-eigen (5) Where: H Fiss-eigen is the initial crack opening; H Fiss-image H is the image crack opening; com is the ratio of the opening degree; the units in the formula are all mm;

[0037] b. Make GR according to the ratio of opening degree and the natural gamma characteristic value of the fracture development section eigen ~H com The intersection diagram, the fitting trend line is established by power function fitting, as shown in formula (6)

[0038]

[0039] Where: a 1 、b 1 is the fitting coefficient;

[0040] c. According to the initial crack opening and the fitting trend line formula (6), determine the first correction formula (7)

[0041]

[0042] Where: H corr-1 is the first calibration result;

[0043] S3.2, First correction of crack data

[0044] The initial crack opening is substituted into formula (7) to realize the first data correction of the crack opening. Through the first crack data correction, the accuracy of the initial crack opening can be improved to be close to the accuracy of the image crack opening.

[0045] According to the electrical imaging crack opening correction method based on image crack segmentation and selection of the present invention, a further preferred technical solution is: step S4 is specifically:

[0046] S4.1, Determination of the second correction formula:

[0047] Based on the image crack opening and the actual crack opening, the second correction formula is determined in the following three steps:

[0048] a. Select crack data that has both image crack opening and actual crack opening corresponding to each other, and calculate the difference in opening using formula (8)

[0049] H diff =H Fiss-image -H actual (8) Where: H Fiss-image H is the image crack opening; actual is the actual crack opening; H diff is the difference in opening degree;

[0050] b. Make H according to the difference in opening and the image crack opening Fiss-image ~H diff The intersection diagram is used to establish the fitting trend line through logarithmic fitting, as shown in formula (9):

[0051] H diff =a 2 ×ln(H Fiss-image )-b 2 (9) Where: H Fiss-image is the image crack opening; a 3 , b 3 is the fitting coefficient; H diff is the difference in opening degree;

[0052] c. According to the image crack opening and the fitting trend line formula (9), determine the second correction formula (10)

[0053] H corr-2 =H Fiss-image -H diff (10) Where: H corr-2 is the second calibration result; H Fiss-image H is the image crack opening; diff is the difference in opening degree; S4.2, the second correction of crack data:

[0054] The first correction result is equivalent to the image crack opening and is substituted into formula (10) to achieve the second data correction of the crack opening, and the accuracy of the initial crack opening is corrected to be the same as the actual crack opening.

[0055] Compared with the prior art, the technical solution of the present invention has the following advantages / benefits:

[0056] 1. The secondary correction method for crack opening proposed in the present invention can correct the crack opening more accurately.

[0057] 2. Improve the accuracy of correction by using electrical imaging data and actual core fracture opening.

[0058] 3. Only 8-20 electrical imaging images of cracks and photos of actual core cracks are needed to correct a large number of crack openings calculated by commercial software. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1 It is a flow chart of the method for correcting the electrical imaging crack opening degree based on image crack segmentation and selection of the present invention.

[0061] Figure 2 It is a schematic diagram of the application of correction data of the electrical imaging crack opening correction method based on image crack segmentation and selection according to the present invention.

[0062] Figure 3 It is a schematic diagram of data processing of electrical imaging crack development segments based on image crack segmentation and selected electrical imaging crack opening correction method of the present invention.

[0063] Figure 4 It is a schematic diagram of crack area segmentation of an electrical imaging picture based on image crack segmentation and the selected electrical imaging crack opening correction method of the present invention.

[0064] Figure 5 It is a schematic diagram of measuring actual fracture opening from core photographs based on image fracture segmentation and selected electrical imaging fracture opening correction method of the present invention.

[0065] Figure 6 It is a schematic diagram of the first correction of crack data according to the method for correcting the electrical imaging crack opening degree based on image crack segmentation and selection of the present invention.

[0066] Figure 7 It is an intersection diagram of the image crack opening and the actual crack opening based on the image crack segmentation and the selected electrical imaging crack opening correction method of the present invention.

[0067] Figure 8 It is a schematic diagram of obtaining natural gamma ray characteristic values ​​of fracture development sections by processing natural gamma ray logging data of fracture development sections in Example 2 of the present invention.

[0068] Fig. 9 It is a schematic diagram of the crack opening degree obtained by processing the electrical imaging picture of the crack in Example 2 of the present invention.

[0069] Fig.10It is a schematic diagram of measuring the actual crack opening by processing actual core crack photos in Example 2 of the present invention.

[0070] Fig.11 It is a schematic diagram of determining the first correction formula of Example 2 of the present invention.

[0071] Fig.12 It is a schematic diagram of the determination of the second correction formula of Example 2 of the present invention.

[0072] Fig.13 This is an electrical imaging picture of crack 1 in Table 1 of Example 2 of the present invention.

[0073] Fig.14 This is an electrical imaging picture of crack 2 in Table 1 of Example 2 of the present invention.

[0074] Fig.15 This is an electrical imaging picture of crack 3 in Table 1 of Example 2 of the present invention.

[0075] Fig.16 This is an electrical imaging picture of crack 4 in Table 1 of Example 2 of the present invention.

[0076] Fig.17 This is an electrical imaging picture of the crack 10 in Table 1 of Example 2 of the present invention.

[0077] Fig.18 This is an electrical imaging picture of the crack 11 in Table 1 of Example 2 of the present invention.

[0078] Fig.19 This is an electrical imaging picture of the crack 12 in Table 1 of Example 2 of the present invention.

[0079] Fig. 20 This is an electrical imaging picture of the crack 23 in Table 1 of Example 2 of the present invention.

[0080] Fig.21 This is an electrical imaging picture of the crack 24 in Table 1 of Example 2 of the present invention.

[0081] Fig. 22 This is an electrical imaging picture of the crack 25 in Table 1 of Example 2 of the present invention. DETAILED DESCRIPTION

[0082] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention.

[0083] Embodiment 1:

[0084] like Figure 1 As shown, an electrical imaging crack opening correction method based on image crack segmentation and selection.

[0085] The specific operation is as follows: S1, obtain data: obtain the initial crack opening (H Fiss-eigen ), natural gamma logging data of fracture development section (GR i ), electrical imaging of cracks (G g ), and cracks

[0086] Electrophysiological images (G g ) Actual core fracture photos corresponding to the depth (G a );

[0087] S2, data processing: S2.1 obtain the gamma ray characteristic value of the fracture development section from the gamma ray (GR) logging data; S2.2 process the electrical imaging image of the fracture to obtain the image fracture opening; S2.3 obtain the actual fracture opening based on the actual core fracture photo;

[0088] S2.1 The specific steps are: process the natural gamma logging data of the fracture development section, and use a single eigenvalue to represent the natural gamma value of the fracture development section.

[0089] The calculation of the natural gamma eigenvalue of the fracture development section includes two steps:

[0090] a. Use the half-width method to read the natural gamma ray (GR) logging data of the fracture development section ( Figure 3 a, b), read the natural gamma value GR in 0.1m intervals i (i=1,2,3,…,n);

[0091] b. Calculate the natural gamma characteristic value of the fracture development section by formula (1) Figure 3 c)

[0092]

[0093] Where: GRi is the natural gamma logging data of the fracture development section, where i = 1, 2, 3, ..., n; GR eigen is the natural gamma ray characteristic value (API) of the fracture development section.

[0094] Step S2.2 includes three steps: image processing to obtain the image crack opening degree in the crack electrical

[0095] Imaging picture G g Based on ( Figure 4 a):

[0096] a. For one of the electrical imaging images of the crack (referring to a selected area, other images or other areas of the same image will be selected at the same time for the same processing to ensure data diversity and result accuracy) that only contains the crack area, draw the R, G, B grayscale histogram of the area ( Figure 4 b), the R grayscale histogram of the area will show a multi-peak distribution, and the grayscale value of the lowest point between the two peaks with the lowest grayscale value

[0097] As the crack grayscale threshold thresh( Figure 4 c);

[0098] b. According to formula (2), the electrical imaging image of the crack is segmented to obtain the electrical imaging crack segmentation image

[0099]

[0100] Where: src is the image gray value matrix; thresh is the crack gray threshold; G Fiss Segmentation images for electrical imaging cracks;

[0101] c. In the electrical imaging crack segmentation image G Fiss Four sampling points of the crack are randomly selected and the crack opening H at the four sampling points is measured. j (j=1, 2, 3, 4) Figure 4 c), the image crack opening H is calculated by formula (3): Fiss-image

[0102]

[0103] Where: l is the diameter of the well; H j is the crack opening of the sampling point, where j = 1, 2, 3, 4; L is the width of the electrical imaging image; H Fiss-image is the image crack opening degree; the unit in the formula is mm.

[0104] In S2.3, the actual fracture opening degree measured by core photographs must be ensured to be within the actual core fracture photograph G aThere are clear and accurate reference objects in the core. a The opening H of the four sampling points of the middle crack photo-i (i=1, 2, 3, 4) and the reference image size L photo ( Figure 5 ), and determine the actual size L of the reference object actual Finally, the actual fracture opening in the core photo is calculated according to formula (4):

[0105]

[0106] Where: H photo-i is the crack photo opening, where i = 1, 2, 3, 4; L photo is the reference image size; L actual is the actual size of the reference object; H actual is the actual opening of the crack; the unit in the formula is mm.

[0107] S3, first correction: perform the first crack correction according to the natural gamma eigenvalue of the crack development section, the initial crack opening and the image crack opening, and obtain the first correction result, so that the accuracy of the initial crack opening is close to the accuracy of the image crack opening;

[0108] Step S3 is specifically as follows:

[0109] S3.1, Determination of the first correction formula:

[0110] The first correction formula is determined based on the natural gamma eigenvalue, initial fracture opening and

[0111] The image crack opening is based on the following three steps:

[0112] a. Based on the initial crack opening and the image crack opening, the opening is calculated by formula (5)

[0113] Degree ratio

[0114] H com =H Fiss-image / H Fiss-eigen (5) Where: H Fiss-eigen is the initial crack opening; H Fiss-image H is the image crack opening; com is the ratio of the opening degree; the units in the formula are all mm;

[0115] b. Make GR according to the ratio of opening degree and the natural gamma characteristic value of the fracture development section eigen ~H com Intersection diagram ( Figure 6a), establish the fitting trend line through power function fitting, as shown in formula (6)

[0116]

[0117] Where: a 1 , b 1 is the fitting coefficient;

[0118] c. According to the initial crack opening and the fitting trend line formula (6), determine the first correction formula (7) ( Figure 6 b)

[0119]

[0120] Where: H corr-1 is the first calibration result;

[0121] S3.2, First correction of crack data

[0122] Substitute the initial crack opening into formula (7) to obtain the first correction result, and realize the first data correction of crack opening ( Figure 6 b), through the first crack data correction, the accuracy of the initial crack opening can be improved to be close to the accuracy of the image crack opening.

[0123] S4, second correction: using the actual crack opening and the image crack opening to obtain the second correction formula, to achieve the correction of the image crack opening to the actual crack opening, and then equating the first correction result to the image crack opening into the correction formula for the second crack correction, to obtain the second correction result, so that the accuracy of the first correction result is close to the accuracy of the actual crack opening. Step S4 is specifically as follows:

[0124] S4.1, Determination of the second correction formula:

[0125] Based on the image crack opening and the actual crack opening, the second correction formula is determined in the following three steps:

[0126] a. Select crack data that has both image crack opening and actual crack opening corresponding to each other, and calculate the difference in opening using formula (8)

[0127] H diff =H Fiss-image -H actual (8) Where: H Fiss-image H is the image crack opening; actual is the actual crack opening; H diff is the difference in opening degree;

[0128] b. Make H according to the difference in opening and the image crack openingFiss-image ~H diff Intersection diagram ( Figure 7 b) Establish the fitting trend line through logarithmic fitting, as shown in formula (9)

[0129] H diff =a 2 ×ln(H Fiss-image )-b 2 (9) Where: H Fiss-image is the image crack opening; a 3 , b 3 is the fitting coefficient; H diff is the difference in opening degree;

[0130] c. According to the image crack opening and the fitting trend line formula (9), determine the second correction formula (10)

[0131] H corr-2 =H Fiss-image -H diff (10) Where: H corr-2 is the second calibration result; H Fiss-image H is the image crack opening; diff is the difference in opening degree; S4.2, the second correction of crack data:

[0132] The first correction result is equivalent to the image crack opening and is substituted into formula (10) to achieve the second data correction of the crack opening, and the accuracy of the initial crack opening is corrected to be close to the accuracy of the actual crack opening.

[0133] Embodiment 2:

[0134] The specific implementation mode of the present invention is described by taking the electrical imaging logging data of a certain region as an example.

[0135] S1, prepare data

[0136] Prepare the fracture development section data containing 25 fractures (selected parts for display, see Table 1), the data includes: ① In the fracture development section, take the fracture development section natural gamma (GR) logging data at intervals of 0.5 meters. i (i=1,2,…,n). ②Analysis software (referring to existing commercial software) crack opening, defined as the initial crack opening H Fiss-eigen ③Electrical imaging of cracks G g ④5 photos of actual core fractures G a .

[0137] S2, Data Processing

[0138] S2.1, Crack GR value processing

[0139] a. Read the natural gamma ray (GR) logging data of the fracture development section using the half-frame method GR i (i = 1, 2, 3, …, n).

[0140] b. Substitute the natural gamma ray (GR) logging data of the fracture development section GR i (i = 1, 2, 3, …, n) into formula (1) to calculate the average value of GR i (i = 1, 2, 3, …, n), and the calculation result is the natural gamma ray (GR) eigenvalue GR corresponding to the initial fracture aperture H Fiss-eigen ( eigen ( Figure 8 ).

[0141] Image data processing

[0142] S2.2. Obtain the image fracture aperture through image processing

[0143] a. For the electrical imaging picture G of the fracture g in which there is only a fracture area ( Fig. 9 a), plot the R, G, and B grayscale histograms of this area, and read the grayscale value at the lowest point between the two peaks in the R grayscale histogram as the fracture grayscale threshold thresh (thresh = 20).

[0144] b. Segment the electrical imaging picture G of the fracture according to formula (2) g to obtain the electrical imaging fracture segmentation image G Fiss ( Fig. 9 c).

[0145] c. Randomly select four sampling points of the fracture in the electrical imaging fracture segmentation image G Fiss and measure the fracture apertures H j (j = 1, 2, 3, 4) at the four sampling points ( Fig. 9 c), and calculate the image fracture aperture H Fiss-image .

[0146] S2.3. Measure the actual fracture aperture from the core photos

[0147] Randomly measure the opening degrees H a of four pictures of the fractures in the actual core fracture photo G photo-i (i = 1, 2, …, 4) and the size L of the reference picture photo , and at the same time determine the actual size L actual of the reference object. Finally, calculate the actual fracture aperture H a in the actual core fracture photo G actual ( Fig.10 ).

[0148] S3, first data correction

[0149] a. Based on the initial crack opening and the image crack opening, the opening ratio is calculated using formula (5).

[0150] b. Opening ratio H com and the natural gamma (GR) characteristic value GR of the fracture development section eigen Making GR eigen ~H com Intersection diagram ( Fig.11 a), establish the fitting trend line through power function fitting, as shown in formula (11).

[0151] H com =5×10 13 ×GR eigen -8.065 (11)

[0152] d. According to the initial crack opening H Fiss-eigen And the fitting trend line formula (11) to determine the first correction formula (formula (12)) ( Fig.11 b).

[0153] H corr-1 =H Fiss-eigen ×5×10 13 ×GR eigen -8.065 (12)

[0154] S4, second data correction

[0155] a. Select crack data that has both image crack opening and actual crack opening corresponding to each other, and calculate the difference in opening using formula (8).

[0156] b. Make H according to the difference in opening and the image crack opening Fiss-image ~H diff Intersection diagram ( Fig.12 b), establish the fitting trend line through logarithmic fitting, as shown in formula (13).

[0157] H diff =2.3569×ln(H Fiss-image )-0.11 (13)

[0158] c. Determine the second correction formula (14) based on the image crack opening and the fitting trend line formula (13).

[0159] H corr-2 =H Fiss-image -2.3569×ln(H Fiss-image )-0.11 (14)

[0160] The first calibration result H corr-1 Equivalent to the image crack opening H Fiss-image Substitute into formula (14) to achieve the second data correction of crack opening. The correction results are shown in Table 1.

[0161] Table 1 Crack correction data table

[0162]

[0163]

[0164]

[0165] It can be seen from the above table that the present invention utilizes the secondary correction method for crack opening to achieve more accurate correction of crack opening.

[0166] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An electrical imaging crack opening correction method based on image crack segmentation and selection, characterized in that: The specific operation is as follows: S1, obtaining data: obtaining the initial fracture opening, natural gamma logging data of the fracture development section, electrical imaging pictures of the fracture, and actual core fracture pictures corresponding to the depth of the electrical imaging pictures of the fracture from the analysis software; S2, data processing: S2.1 obtain the natural gamma characteristic value of the fracture development section from the natural gamma logging data of the fracture development section; S2.2 The electrical imaging image of the crack is processed to obtain the image crack opening; S2.3 Obtain the actual fracture opening according to the actual core fracture photos; S3, first correction: perform the first crack correction according to the natural gamma eigenvalue of the crack development section, the initial crack opening and the image crack opening, and obtain the first correction result, so that the accuracy of the initial crack opening is close to the accuracy of the image crack opening; S4, second correction: the second correction formula is obtained using the actual crack opening and the image crack opening to realize the correction of the image crack opening to the actual crack opening, and then the first correction result is equated with the image crack opening and substituted into the second correction formula for the second crack correction to obtain the second correction result, so that the accuracy of the first correction result is close to the accuracy of the actual crack opening.

2. The electrical imaging crack opening correction method based on image crack segmentation and selection according to claim 1 is characterized in that: S2.1 The specific steps are: process the natural gamma logging data of the fracture development section, and use a single eigenvalue to represent the natural gamma value of the fracture development section.

3. The electrical imaging crack opening correction method based on image crack segmentation and selection according to claim 1 or 2, characterized in that: The calculation of the natural gamma eigenvalue of the fracture development section includes two steps: a. Use the half-width method to read the natural gamma logging data of the fracture development section, and read the natural gamma value in 0.1m intervals; b. Calculate the natural gamma characteristic value of the fracture development section using formula (1) Where: GR i is the natural gamma logging data of the fracture development section, where i = 1, 2, 3, ..., n; GR eigen is the natural gamma eigenvalue of the fracture development section.

4. The method for correcting crack opening degree by electrical imaging based on image crack segmentation and selection according to claim 1, characterized in that: Step S2.2 includes three steps: a. For a crack area in the electrical imaging image of the crack, draw the R, G, and B grayscale histograms of the area. The R grayscale histogram of the area will show a multi-peak distribution. The grayscale value of the lowest point between the two peaks with the lowest grayscale values ​​is used as the crack grayscale threshold; b. According to formula (2), the electrical imaging image of the crack is segmented to obtain the electrical imaging crack segmentation image Where: src is the image gray value matrix; thresh is the crack gray threshold; G Fiss Segmentation images for electrical imaging cracks; c. Randomly select four sampling points of the crack in the electrical imaging crack segmentation image, measure the crack opening at the four sampling points, and calculate the image crack opening by formula (3): Where: l is the diameter of the well; H j is the crack opening of the sampling point, where j = 1, 2, 3, 4; L is the width of the electrical imaging image; H Fiss-image is the image crack opening degree; the unit in the formula is mm.

5. The method for correcting crack opening degree by electrical imaging based on image crack segmentation and selection according to claim 1, characterized in that: In S2.3, in order to ensure that there is a clear and accurate reference in the actual core fracture photo, the opening of the fracture at four sampling points in the actual core fracture photo and the size of the reference image are measured, and the actual size of the reference is determined at the same time. Finally, the actual fracture opening in the core photo is calculated according to formula (4): Where: H photo-i is the crack photo opening, where i = 1, 2, 3, 4; L photo is the reference image size; L actual is the actual size of the reference object; H actual is the actual opening of the crack; the unit in the formula is mm.

6. The method for correcting crack opening degree by electrical imaging based on image crack segmentation and selection according to claim 1, characterized in that: Step S3 is specifically as follows: S3.1, Determination of the first correction formula: The determination of the first correction formula is based on the natural gamma eigenvalue of the fracture development section, the initial fracture opening and the image fracture opening, and is divided into the following three steps: a. Based on the initial crack opening and the image crack opening, the opening ratio is calculated using formula (5): H com =H Fiss-image / H Fiss-eigen (5) Where: H Fiss-eigen is the initial crack opening; H Fiss-image H is the image crack opening; com is the ratio of the opening degree; the units in the formula are all mm; b. Make GR according to the ratio of opening degree and the natural gamma characteristic value of the fracture development section eigen ~H com The intersection diagram, the fitting trend line is established by power function fitting, as shown in formula (6) In the formula: a1, b1 are fitting coefficients; c. According to the initial crack opening and the fitting trend line formula (6), determine the first correction formula (7) Where: H corr-1 is the first calibration result; S3.2, First correction of crack data The initial crack opening is substituted into formula (7) to realize the first data correction of the crack opening. Through the first crack data correction, the accuracy of the initial crack opening can be improved to be close to the accuracy of the image crack opening.

7. The method for correcting crack opening degree by electrical imaging based on image crack segmentation and selection according to claim 1, characterized in that: Step S4 is specifically as follows: S4.1, Determination of the second correction formula: Based on the image crack opening and the actual crack opening, the second correction formula is determined in the following three steps: a. Select crack data that has both image crack opening and actual crack opening corresponding to each other, and calculate the difference in opening using formula (8) H diff =H Fiss-image -H actual (8) Where: H Fiss-image H is the image crack opening; actual is the actual crack opening; H diff is the difference in opening degree; b. Make H according to the difference in opening and the image crack opening Fiss-image ~H diff The intersection diagram is used to establish the fitting trend line through logarithmic fitting, as shown in formula (9): H diff =a2×ln(H Fiss-image )-b2 (9) Where: H Fiss-image is the image crack opening degree; a3 and b3 are fitting coefficients; H diff is the difference in opening degree; c. According to the image crack opening and the fitting trend line formula (9), determine the second correction formula (10) H corr-2 =H Fiss-image -H diff (10) Where: H corr-2 is the second calibration result; H Fiss-image H is the image crack opening; diff is the difference in opening degree; S4.2, Second correction of crack data: The first correction result is equivalent to the image crack opening and is substituted into formula (10) to achieve the second data correction of the crack opening, and the accuracy of the initial crack opening is corrected to be close to the accuracy of the actual crack opening.

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