Cross-hole fracture clustering method based on fracture coplanarity index

Abstract

The invention provides a cross-hole fracture clustering method based on a fracture coplanarity index, and the method comprises the steps: selecting a target region drill hole group, carrying out the image processing of a target region drill hole image, obtaining the geometric parameters of a drill hole fracture trace, generating all fracture surface equations in a single hole, and correcting the equations based on the drill hole parameters, calculating the coplanarity index of the fractures of the two drill holes, sequentially carrying out coplanarity judgment on all fracture surfaces of the target drill hole and all fracture surfaces of the adjacent drill holes according to the coplanarity indexes, and clustering the fractures of which the coplanarity indexes of the fracture surfaces in the two adjacent holes are greater than a coplanarity threshold value, and determining a fracture surface boundary based on a cross-hole fracture clustering result and generating a fracture network model. According to the method, the regional discrete fracture network model can be established, and the method is used for generating and analyzing the fracture network model between the drilling regions and is convenient to use.

Description

Technical Field

[0001] The invention relates to the technical field of rock mass cross-pore fracture clustering, and in particular to a cross-pore fracture clustering method based on fracture coplanarity index. Background Art

[0002] Most water conservancy and hydropower projects are built in mountain valleys. The geometric configuration of joints and fissures in the rock mass is very complex and difficult to observe directly, which makes the foundation engineering involving fracture network rock mass hidden. The existence of fractures leads to the anisotropy and heterogeneity of the rock mass. At the same time, the fractures also dominate the seepage characteristics of the rock mass. The bedrock seepage problem caused by fractures in the rock mass brings huge challenges to the construction of water conservancy projects. Discrete fracture network is a common method for analyzing seepage. The geometric parameters of borehole fractures are crucial to the establishment of discrete fracture network models based on borehole data. However, to establish a discrete fracture network model, it is necessary to obtain borehole fracture images. The existing borehole fracture image recognition is only for a single borehole. The single-hole fracture model can be established through a series of operations such as image recognition, skeletonization algorithm, and single-hole clustering. However, the obtained fracture model only represents the area where the single hole is located, and does not involve multiple holes, especially the fracture model generation and analysis of the area between boreholes. Therefore, it is not conducive to analyzing the structure and development of regional fractures. Therefore, it is necessary to design a cross-pore fracture clustering method based on the fracture coplanarity index. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a cross-pore fracture clustering method based on fracture coplanarity index.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a cross-pore fracture clustering method based on fracture coplanarity index, comprising:

[0006] Drilling clusters in selected target areas;

[0007] The target area drilling images are processed and the geometric parameters of the drilling fracture traces are obtained, and the fracture surface equations of all the fractures in a single hole are generated and corrected based on the drilling parameters;

[0008] Calculate the coplanarity index of the two borehole fractures;

[0009] All fracture surfaces of the target borehole and all fracture surfaces of adjacent boreholes are judged for coplanarity in turn according to the coplanarity index, and fractures whose coplanarity index of fracture surfaces in two adjacent boreholes is greater than the coplanarity threshold are clustered;

[0010] The fracture surface boundaries are determined based on the cross-pore fracture clustering results and a fracture network model is generated.

[0011] Preferably, the target area drilling images are processed and the drilling fracture trace geometric parameters are obtained, and all fracture surface equations in a single hole are generated and corrected based on the drilling parameters, specifically:

[0012] According to the open source DeepLabV3+, the cracks in the borehole images are identified, the pixels in the crack area in the image are efficiently segmented, and the binary image of the cracks and the rock background is obtained;

[0013] The cracks in the binary image are skeletonized according to the identification, and the burr method is used to eliminate the burrs generated in the skeletonization process to obtain a complete skeleton crack without burrs;

[0014] Based on the least squares method, the segmented fracture fitting plane is obtained, and the coplanarity error between each fracture segment and other fracture segments is calculated. If it is less than the set threshold, the fractures are clustered into the same type, the skeleton fracture clustering is completed, and a three-dimensional fracture coplanar map is generated;

[0015] Based on the three-dimensional fracture surface equation after skeleton fracture clustering, the fracture surface characteristic parameters are obtained;

[0016] Correct the characteristic parameters of the fracture surface;

[0017] The corrected fracture surface equation is calculated based on the corrected fracture surface characteristic parameters.

[0018] Preferably, based on the three-dimensional crack surface equation after skeleton crack clustering, the crack surface characteristic parameters are obtained, specifically:

[0019] Establish a coordinate system, select the center point of the target borehole as the coordinate origin, and define the east direction, north direction, and vertical upward direction as the positive directions of the x-axis, y-axis, and z-axis, respectively, to determine the coordinates of the center point of the borehole O(0,0,0);

[0020] Select the coordinates of the intersection of the fracture surface and the centerline of the borehole, that is, the coordinates of the fracture center point M 0 (0,0,h) is used as the coordinate of the required point on the fracture surface, where h is the distance from the center point of the borehole to the intersection of the fracture surface and the centerline of the borehole, that is, the fracture surface depth. 0 The normal vector of the crack surface S is obtained by using the point coordinates and the crack surface equation

[0021] Preferably, the characteristic parameters of the fracture surface are corrected, specifically:

[0022] Get drilling data, including top angle θ 1 and azimuth angle θ 2 , the calculated axis direction vector Combined with the hole coordinates O(0,0,0), the drilling axis equation is:

[0023]

[0024] The depth of the center of the crack is known to be h. Substituting t = h into the equation of the borehole axis, the coordinates of the center of the borehole can be obtained: 1 (x 1 ,y 1 ,z 1 ), where x 1 =dsinθ 1 sinθ 2 ,y 1 =dsinθ 1 cosθ 2 , z 1 =dcosθ 1 ;

[0025] Find the direction vector along the negative z-axis Rotate to The corresponding rotation matrix R is:

[0026]

[0027] In the formula, θ 1 The negative direction vector of the z-axis arrive The rotation angle, that is, the vertex angle θ 1 , r is the negative direction vector of the z-axis and The cross product vector of Apply the same rotation to get the corrected normal vector of the crack surface in

[0028] Preferably, the corrected fracture surface equation is calculated based on the corrected fracture surface characteristic parameters, specifically:

[0029] According to the coordinates of the center point of the crack surface after correction, M 1 (x 1 ,y 1 ,z 1 ), the corrected fracture surface normal vector Solving the plane equation according to the point method, the corrected crack surface equation is:

[0030] n x (xx 1 )+n y (yy 1 )+n z (zz 1 )=0

[0031] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0032] The present invention provides a cross-hole fracture clustering method based on fracture coplanarity index, the method comprising: selecting a target area borehole group, performing image processing on the target area borehole images respectively and obtaining the geometric parameters of the borehole fracture traces, generating all fracture surface equations in a single hole and correcting them based on the drilling parameters, calculating the coplanarity index of the fractures of two boreholes, judging the coplanarity of all fracture surfaces of the target borehole and all fracture surfaces of adjacent boreholes in turn according to the coplanarity index, clustering the fractures whose coplanarity index of the fracture surfaces in two adjacent holes is greater than the coplanarity threshold, determining the fracture surface boundary based on the cross-hole fracture clustering result and generating a fracture network model. The present invention can establish a regional discrete fracture network model, which is used for the generation and analysis of fracture network models between borehole regions and is easy to use; the innovation of the present invention is that the coordinates of the points for determining the plane equation and the plane normal vector are obtained based on the inclined hole. Compared with the traditional method of obtaining the fracture surface of the vertical hole, this method is more in line with the actual situation, and the accuracy of the obtained borehole fracture surface data is improved to a certain extent; the present invention defines a cross-hole fracture coplanarity index, and realizes the acquisition of fracture information between adjacent boreholes. The specific implementation process is to make a judgment based on the coplanarity index, as shown in the accompanying drawings of the specification. Figure 3 As shown in the figure, if the cracks between two adjacent boreholes are clustered into the same crack plane, then the cracks in the area between them must also be on this crack plane, and then the relevant information of the cracks in the area between the boreholes can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 This is the preprocessing diagram of single-hole fracture clustering;

[0035] Figure 2 It is the correction diagram of single fracture hole parameters based on hole inclination;

[0036] Figure 3 is the cross-pore fracture coplanarity parameter diagram;

[0037] Figure 4 is the crack boundary map;

[0038] Figure 5 Generate plots for cross-pore fracture models;

[0039] Figure 6 A flow chart of a method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The purpose of the present invention is to provide a cross-hole fracture clustering method based on fracture coplanarity index, which can establish a regional discrete fracture network model for the generation and analysis of fracture network models between drilling areas and is easy to use.

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Figure 6 A flow chart of a method provided by an embodiment of the present invention, such as Figure 6 As shown, the present invention provides a cross-pore fracture clustering method based on fracture coplanarity index, comprising:

[0044] Step 100: Select a target area drilling group;

[0045] Step 200: performing image processing on the target area drilling images respectively and obtaining the geometric parameters of the drilling fracture traces, generating all fracture surface equations in a single hole and correcting them based on the drilling parameters;

[0046] Step 300: Calculate the coplanarity index of the two borehole fractures;

[0047] Step 400: all fracture surfaces of the target borehole and all fracture surfaces of adjacent boreholes are judged for coplanarity in turn according to the coplanarity index, and fractures in two adjacent boreholes whose coplanarity index of fracture surfaces is greater than the coplanarity threshold are clustered;

[0048] Step 500: Determine the fracture surface boundary and generate a fracture network model based on the cross-pore fracture clustering results.

[0049] In step 200, the target area drilling images are processed and the geometric parameters of the drilling fracture traces are obtained, and all fracture surface equations in a single hole are generated and corrected based on the drilling parameters, specifically:

[0050] Step 201: According to the open source DeepLabV3+, the cracks in the borehole image are identified, and the pixels in the crack area in the image are efficiently segmented to obtain a binary image of the cracks and the rock background. Figure 1 (b)

[0051] Step 202: skeletonize the cracks in the binary image obtained by identification, and use a burr method to eliminate the burrs generated during the skeletonization process to obtain a complete skeleton crack without burrs. Figure 1 (c)

[0052] Step 203: Based on the least squares method, the segmented fracture fitting plane is obtained, and the coplanarity error between each fracture segment and other fracture segments is calculated. If the error is less than the set threshold, the fractures are clustered into the same type, the skeleton fracture clustering is completed, and a three-dimensional fracture coplanar map is generated. Figure 1 (d) and (e);

[0053] Step 204: based on the three-dimensional fracture surface equation after skeleton fracture clustering, obtain fracture surface characteristic parameters (such as fracture surface normal vector and drilling fracture surface center point position);

[0054] Step 205: Correcting the characteristic parameters of the fracture surface;

[0055] Step 206: Calculate a corrected fracture surface equation based on the corrected fracture surface characteristic parameters.

[0056] In step 204, based on the three-dimensional fracture surface equation after skeleton fracture clustering, fracture surface characteristic parameters are obtained, specifically:

[0057] like Figure 2 As shown, a coordinate system is established, the center point of the target borehole is selected as the coordinate origin, and the east direction, north direction, and vertical upward direction are respectively defined as the positive directions of the x-axis, y-axis, and z-axis, and the coordinate of the center point of the borehole is determined to be O(0,0,0);

[0058] Select the coordinates of the intersection of the fracture surface and the centerline of the borehole, that is, the coordinates of the fracture center point M 0 (0,0,h) is used as the coordinate of the required point on the fracture surface, where h is the distance from the center point of the borehole to the intersection of the fracture surface and the centerline of the borehole, that is, the fracture surface depth. 0 The normal vector of the crack surface S is obtained by using the point coordinates and the crack surface equation

[0059] In step 205, the characteristic parameters of the fracture surface are modified, specifically:

[0060] The fracture surface characteristic parameters obtained are based on vertical drilling conditions. In actual field conditions, the drilling direction often has a certain angle with the vertical direction, which is inconsistent with the actual situation, so it needs to be corrected;

[0061] Get drilling data, including top angle θ 1 and azimuth angle θ 2 , the calculated axis direction vector Combined with the hole coordinates O(0,0,0), the drilling axis equation is:

[0062]

[0063] The depth of the center of the crack is known to be h. Substituting t = h into the equation of the borehole axis, the coordinates of the center of the borehole can be obtained: 1 (x 1 ,y 1 ,z 1 ), where x 1 =dsinθ 1 sinθ 2 ,y 1 =dsinθ 1 cosθ 2 , z 1 =dcosθ 1 ;

[0064] Find the direction vector along the negative z-axis Rotate to The corresponding rotation matrix R is:

[0065]

[0066] In the formula, θ 1 The negative direction vector of the z-axis arrive The rotation angle, that is, the vertex angle θ 1 , r is the negative direction vector of the z-axis and The cross product vector of Apply the same rotation to get the corrected normal vector of the crack surface in

[0067] In step 206, a corrected fracture surface equation is calculated based on the corrected fracture surface characteristic parameters, specifically:

[0068] According to the coordinates of the center point of the crack surface after correction, M 1 (x 1 ,y 1 ,z 1 ), the corrected fracture surface normal vector Solving the plane equation according to the point method, the corrected crack surface equation is:

[0069] n x (xx 1 )+n y (yy 1 )+n z (zz 1 )=0

[0070] In step 300, the coplanarity index of the two borehole fractures is calculated, specifically:

[0071] Assume that borehole A and borehole B reveal two fracture surfaces respectively, and the corresponding fracture surfaces are l 1 , l 2 First, determine the position relationship of the two fracture surfaces. If they intersect, the intersection line is L. The center line of the two boreholes is L. 1 , l 2 The intersection point is C 1 , C 2 ,like Figure 3 As shown;

[0072] In this study, a straight line on any fracture surface parallel to L and intersecting the midlines of the two boreholes is selected as the rotation axis, and the rotation angle is recorded as θ. Figure 3 The influence of spatial freedom on the translation distance after rotation determines the choice of C 1 , C 2 The direction of the line segment after the projection of the connecting line on the plane perpendicular to L is taken as the translation direction, and the translation distance is recorded as d. In the figure, d can be obtained from the geometric relationship of the triangle:

[0073] d=H[tan(γ+θ)-tanγ]

[0074] Where H is L to L 0 The vertical distance, L 0 is a straight line passing through the midpoint of the line connecting the two orifices A and B and parallel to the borehole; γ is the elevation angle, which is the fracture surface l 2 The angle between L and plane I. The spatial position of plane I can be determined by the position of plane I and the horizontal plane, where the angle between plane I and the horizontal plane is equal to the angle between L and the horizontal plane.

[0075] According to the above description of the geometric relationship between the two fracture surfaces, the evaluation index ε describing the coplanarity of the two fracture surfaces is defined as:

[0076]

[0077] Where D is the distance between two drilling holes, in m;

[0078] If the two fracture surfaces are parallel, θ=0. At this time, no rotation is required. Only translation is needed to make the two fracture surfaces coincide. The translation direction is the perpendicular direction of the two fracture surfaces. The translation distance can be calculated according to the distance formula of parallel planes in mathematics.

[0079] In step 500, the fracture surface boundary is determined based on the cross-pore fracture clustering result and a fracture network model is generated, specifically:

[0080] The present invention assumes that the crack boundary shape is an irregular polygon. Figure 4 Different fracture boundary definition methods are shown to determine the fracture surface boundaries of adjacent cross-hole regions;

[0081] According to the above method, the deterministic equation of each fracture surface in the study area can be determined, and then all fracture surface equations can be used to generate a deterministic fracture network model, such as Figure 5 shown.

[0082] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0083] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A cross-pore fracture clustering method based on fracture coplanarity index, characterized in that: include: Drilling clusters in selected target areas; The target area drilling images are processed and the geometric parameters of the drilling fracture traces are obtained, and the fracture surface equations of all the fractures in a single hole are generated and corrected based on the drilling parameters; Calculate the coplanarity index of the two borehole fractures; All fracture surfaces of the target borehole and all fracture surfaces of adjacent boreholes are judged for coplanarity in turn according to the coplanarity index, and fractures whose coplanarity index of fracture surfaces in two adjacent boreholes is greater than the coplanarity threshold are clustered; The fracture surface boundaries are determined based on the cross-pore fracture clustering results and a fracture network model is generated.

2. The method according to claim 1, characterized in that: The drilling images of the target area are processed and the geometric parameters of the drilling fracture traces are obtained. The fracture surface equations of all the fractures in a single hole are generated and corrected based on the drilling parameters. Specifically, According to the open source DeepLabV3+, the cracks in the borehole images are identified, the pixels in the crack area in the image are efficiently segmented, and the binary image of the cracks and the rock background is obtained; The cracks in the binary image are skeletonized according to the identification, and the burr method is used to eliminate the burrs generated in the skeletonization process to obtain a complete skeleton crack without burrs; Based on the least squares method, the segmented fracture fitting plane is obtained, and the coplanarity error between each fracture segment and other fracture segments is calculated. If it is less than the set threshold, the fractures are clustered into the same type, the skeleton fracture clustering is completed, and a three-dimensional fracture coplanar map is generated; Based on the three-dimensional fracture surface equation after skeleton fracture clustering, the fracture surface characteristic parameters are obtained; Correct the characteristic parameters of the fracture surface; The corrected fracture surface equation is calculated based on the corrected fracture surface characteristic parameters.

3. The method according to claim 2, characterized in that Based on the three-dimensional fracture surface equation after skeleton fracture clustering, the fracture surface characteristic parameters are obtained, which are: Establish a coordinate system, select the center point of the target borehole as the coordinate origin, and define the east direction, north direction, and vertical upward direction as the positive directions of the x-axis, y-axis, and z-axis, respectively, to determine the coordinates of the center point of the borehole O(0,0,0); Select the coordinates of the intersection of the fracture surface and the centerline of the borehole, that is, the coordinates of the fracture center point M0 (0,0,h) as the coordinates of the required point on the fracture surface, where h is the distance from the center point of the borehole mouth to the intersection of the fracture surface and the centerline of the borehole, that is, the depth of the fracture surface. According to the coordinates of point M0 and the fracture surface equation, the normal vector S of the fracture surface is obtained.

4. The method according to claim 3, characterized in that The characteristic parameters of the fracture surface are modified as follows: Get drilling data, including vertex angle θ1 and azimuth angle θ2, and calculate the axis direction vector Combined with the hole coordinates O(0,0,0), the drilling axis equation is: It is known that the depth of the center of the crack is h. Substituting t=h into the equation of the borehole axis, the coordinates of the center of the borehole M1(x1, y1, z1) can be obtained, where x1=dsinθ1sinθ2, y1=dsinθ1cosθ2, z1=dcosθ1; Find the direction vector along the negative z-axis Rotate to The corresponding rotation matrix R is: In the formula, θ1 is the negative direction vector of the z-axis arrive The rotation angle, that is, the vertex angle θ1, r is the direction vector in the negative direction of the z-axis and The cross product vector of Apply the same rotation to get the corrected normal vector of the crack surface in 5. The method according to claim 4, characterized in that The corrected fracture surface equation is calculated based on the corrected fracture surface characteristic parameters, specifically: According to the coordinates of the center point of the corrected fracture surface as M1 (x1, y1, z1), the corrected fracture surface normal vector Solving the plane equation according to the point method, the corrected crack surface equation is: n x (x-x1)+n y (y-y1)+n z (z-z1)=0。

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