A 3D geological modeling method for steeply inclined strata

Abstract

The present invention belongs to the technical field of large-scale three-dimensional geological model construction and spatial visualization analysis in the construction scenario of underground engineering, and particularly relates to a three-dimensional geological modeling method for steeply inclined strata, comprising the following steps: Step 1: Establish a steeply inclined strata model that conforms to the strike and dip constraints; Step 2: Solve the intersection line between the unconformity surface and the steeply inclined strata surface to complete the three-dimensional geological construction of the steeply inclined strata and the unconformity contact surface. The said Step 1 includes the following steps: Step 101: Organize the plane geological map and strata description data of the modeling target area, and extract the strike line vector graph of the steeply inclined strata in the modeling target area; Step 102: According to the strike line vector graph, perform equally spaced sampling on the strike line, and extract the plane coordinate set {P n} = {X s , Y s}. The present invention can significantly reduce the type and amount of the original modeling data, greatly reduce the modeling steps and shorten the modeling process, and effectively improve the modeling efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of large-scale three-dimensional geological model construction and spatial visualization analysis in the construction scenario of underground engineering, and particularly relates to a three-dimensional geological modeling method for steeply inclined strata. Background Art

[0002] Three-dimensional geological modeling is a work highly dependent on data. A good three-dimensional geological model requires a large amount of basic data as support. When existing three-dimensional geological modeling software constructs a stratum structure model, there are usually two methods. One is to use borehole data for modeling. In this method, it is necessary to extract stratum layering control points from the borehole data and implicitly model the stratum surface by means of an interpolation algorithm to obtain the three-dimensional stratum surface. When the borehole data is rich, this method can obtain a good modeling effect. However, when the borehole data in the target area is sparse, it is not sufficient to constrain the interpolation algorithm, and the stratum modeling accuracy is poor. The other method is to use three-dimensional seismic data for modeling, and model based on the surface data obtained from three-dimensional seismic interpretation. The spatial point cloud data of the stratum and fault surfaces are used to control the generation of the three-dimensional models of the stratum and faults. This method combines well logging interpretation and three-dimensional seismic data and can obtain a relatively accurate three-dimensional geological model. In the case where the target stratum is buried deep and the drilling cost is too high, this method can achieve good cost control and a good modeling effect, so it is widely used in three-dimensional geological modeling of oil reservoirs.

[0003] Due to the influence of fold tectonic movements, the dip angles of the strata on both wings of the fold change after long-term geodynamic transformation. If the strata are strongly squeezed by the fold, the dip angle change is large. If the work area for geological modeling is on one wing of a syncline or anticline, the target stratum appears as a monoclinic stratum with a large dip angle. When the stratum dip angle is greater than 45°, it is called a steeply inclined stratum.

[0004] Steeply inclined strata are widespread, which has an adverse impact on the construction of underground projects such as subway tunnel shield and mineral resource extraction. When using conventional three-dimensional geological modeling software to model such steeply inclined strata, it is difficult to accurately obtain a model that conforms to the actual situation. The above two methods mainly show the following limitations when modeling steeply inclined strata:

[0005] 1) Different interpolation methods have specific requirements for the data used in modeling. When constructing a stratum model based on borehole data, the distribution of the stratum is controlled by the characteristics of the stratum layering data in the borehole. When the amount of borehole and layering data is scarce, due to algorithm limitations, it is difficult to guarantee the accuracy of interpolation.

[0006] 2) When using interpolation methods in a limited number of data points, such as the minimum curvature, DSI and other methods, their smoothing effects will seriously affect the model accuracy in the interpolation area, and the steeply inclined characteristics of the stratum cannot be reflected, and phenomena such as surface distortion, holes, and intersections will occur.

[0007] 3) When modeling steeply dipping strata and unconformity contact relationships, the existing intersection line algorithms have high algorithm complexity and are not conducive to implementation. For example, a method for calculating the intersection line of free-form surfaces proposed in Chinese Patent CN202210319642.2 uses the Newton-Raphson iteration method to obtain the intersection line of two free-form surfaces. However, since this method requires solving first-order and second-order partial derivatives and the Hessian matrix, the algorithm complexity is relatively high and it is not conducive to program implementation.

[0008] Therefore, there is an urgent need for a method that is applicable to the lack of 3D seismic interpretation data, can solve the problem of sparse borehole data, and can better realize the modeling of steeply dipping strata to solve the large-scale 3D geological modeling problem in engineering application scenarios. Summary of the Invention

[0009] The purpose of the present invention is to provide a 3D geological modeling method for steeply dipping strata, which can significantly reduce the type and amount of original modeling data, greatly reduce the modeling steps, shorten the modeling process, and effectively improve the modeling efficiency.

[0010] The technical solutions adopted by the present invention are specifically as follows:

[0011] A 3D geological modeling method for steeply dipping strata includes the following steps:

[0012] Step 1: Establish a steeply dipping strata model that meets the strike and dip constraints;

[0013] The said Step 1 includes the following steps:

[0014] Step 101: Extract the vector graph of the strike line of the steeply dipping strata in the modeling target area;

[0015] Step 102: According to the vector graph of the strike line, perform equally spaced sampling on the strike line, and extract the set of plane coordinates of the strike line {P n} = {X s , Y s} as the basic data set for 3D surface interpolation of the strata;

[0016] Step 104: Extract the stratified data points of the modeling target strata from the borehole columnar diagram in the target area to establish an expanded borehole data set;

[0017] Step 105: Establish a 3D strata surface using the centerline method;

[0018] Step 106: Use the dip and dip angle constraints to establish a 3D layer line array of the strata;

[0019] Step 107: Use the delaunay triangulation algorithm to triangulate the surface line array to form a triangular mesh;

[0020] Step 108: Based on the vertex dataset of the triangular mesh and combined with the borehole expansion dataset extracted in Step 104, form the control point dataset of the steeply inclined strata surface;

[0021] Step 2: Solve the intersection line of the unconformity surface and the steeply inclined strata surface to complete the 3D geological modeling of the steeply inclined strata and the unconformity contact surface;

[0022] The said Step 2 includes the following steps:

[0023] Step 201: Respectively set the main and secondary surfaces for the surfaces to be calculated, where the main surface is the cutting surface and the secondary surface is the surface to be cut and trimmed, and through coordinate intersection operation, obtain [X AC , Y AC , Z AC ;

[0024] The said Step 201 includes the following steps:

[0025] Set the triangular mesh vertex set of the main surface as f A (X, Y, Z), and the coordinate range is [X A , Y A , Z A , and set the triangular mesh vertex set of the secondary surface as f C (X, Y, Z), and the coordinate range is [X C , Y C , Z C , through coordinate intersection operation, the complete coordinate set [X AC , Y AC , Z AC , Z AC containing the intersection line L

[0026] Step 202: Perform uniform grid meshing on the coordinate set [X AC , Y AC , Z AC , set the grid spacing as (ΔX AC , ΔY AC , ΔZ AC ), and the grid spacings in the three-axis directions are the same. The number of grid cells in the X, Y, and Z coordinate axes directions are respectively denoted as (m, n, p);

[0027] Step 203: Set the error threshold as Calculate that if it is less than the error threshold, it is considered that the grid cells coincide;

[0028] Step 204: Substitute the coordinates of the grid cell into f A (X, Y, Z) and f C(X, Y, Z), if and then this grid cell is on the intersection line of surfaces A and C and is marked;

[0029] Step 205: Traverse all grid cells to complete the marking of grid cells on the intersection line of surfaces;

[0030] Step 206: Use the triangle intersection algorithm to find the intersection points, and add the intersection points to the triangular meshes of the two intersecting strata models respectively. If the intersection point is inside the triangle, new coordinate points are added inside; if the intersection point is on the side of the triangle, a new point is added at this point to divide this side;

[0031] Step 207: Connect the vertices of the triangular mesh to construct new triangles, and use Delaunay triangulation to perform local reconstruction of the main and slave surfaces;

[0032] Step 208: Mark and delete the sub-regions of the surface according to the stratigraphic sequence and sedimentary relationship to complete the 3D geological modeling of the steeply inclined strata and the unconformity contact surface.

[0033] Furthermore, the strike line vector graph in step 101 is extracted according to the plane geological map and stratigraphic description data of the modeling target area.

[0034] Furthermore, between step 101 and step 104, there is also included:

[0035] Step 103: Perform curvature constraint on the strike data.

[0036] Furthermore, step 103 includes the following steps:

[0037] Obtain the B-spline curve equation passing through the strike sampling points by data fitting, denoted as y = f(x). Starting from one end of the strike line as the starting point A, every three adjacent points are used to calculate the curvature, and traverse to the other end point B of the curve. Let the curvature at the point Pi(x0, y0) be:

[0038]

[0039] Obtain the curvature set {κ1, κ2,..., κ n-2} of the strike curve by calculating through formula (1).

[0040] Furthermore, the borehole expansion data set in step 104 includes borehole name, hole mouth coordinates, formation name, layer depth measurement or elevation.

[0041] Furthermore, step 105 includes the following steps:

[0042] Step 105a: According to the modeling depth range {Z top , Zbottom}The calculated center line

[0043] Step 105b: Combine the plane coordinate set of the strike line in Step 102, add the Z coordinate to the strike line coordinate set, and establish the three-dimensional coordinate set [X of the formation center line s , Y s , Z center .

[0044] Furthermore, the said Step 108 includes the following steps:

[0045] For each vertex on the grid, take a neighborhood B around the point, and the taking method is to satisfy all points whose distance to the point is less than or equal to the given distance d, and define the following matrix:

[0046]

[0047] where, |B| is the area of B; e is the edge of the grid in B; is the unit vector in the direction of e; ||e∩B|| is the length of e∩B, which is between 0 and |e|; β(e) is the included angle between the two normal triangles with e as the common side;

[0048] Examine the eigenvalues and eigen-directions of the above matrix, the minimum eigenvalue and eigen-direction of are used as the estimation formula of the normal vector of the grid surface at the vertex p i , and the minimum eigenvalue and the maximum eigenvalue are used as the estimation formulas of the principal curvatures κ1 and κ2. Then the mean curvature K H and the Gaussian curvature K G are directly obtained from the principal curvatures according to the theory of differential geometry:

[0049]

[0050] Use the mean curvature to smooth the surface, and generate a three-dimensional formation surface that not only conforms to the formation strike and dip laws but also can satisfy the formation stratification positions revealed by boreholes.

[0051] The technical effects achieved by the present invention are:

[0052] (1) The present invention uses the strike line of the formation as the basic data for surface interpolation to achieve the purpose of expanding the interpolation sample set, uses the dip angle for the normal constraint in three-dimensional surface interpolation, and combines borehole data to expand the set of layer control points, improves the local accuracy, and uses the strike and dip constraints for three-dimensional interpolation of the formation surface, which preferably solves the problem of sparse or even missing borehole and formation stratification data, can preferably solve the problem of sparse modeling data, and effectively improves the interpolation effect of sparse borehole data.

[0053] (2) The present invention realizes the solution algorithm for the intersection line of formation surfaces based on a grid method, without the need for partial derivatives and matrix operations. The algorithm complexity is extremely low, and it has the characteristics of natural discreteness, making it easy to be implemented by programming.

[0054] (3) The present invention introduces the idea of collision detection in computer-aided design, establishes bounding boxes for formation models that may intersect, constructs an octree to screen the bounding boxes where potential intersecting triangles are located, then equally divides the space occupied by the bounding boxes into small cubes, establishes a triangle spatial index. If triangles from two models are contained in the same cube, the intersection line of the two triangles is calculated. This method simplifies the solution of the intersection line of different surfaces to the intersection of intersecting triangles, can quickly exclude non-intersecting triangles, improves the operation efficiency, is applicable to the reconstruction of the contact relationship of steeply inclined formation models, and can meet the requirements of fault-cut sedimentary formation modeling. Brief Description of the Drawings

[0055] Figure 1 is a schematic diagram of the steeply inclined formation of the present invention;

[0056] Figure 2 is a schematic diagram of the set of sampling points of the strike line of the present invention;

[0057] Figure 3 is a schematic diagram of the curvature calculation of the curve of the present invention;

[0058] Figure 4 is a schematic diagram of the array of layer lines with strike, dip and dip angle constraints of the present invention;

[0059] Figure 5 is a schematic diagram of the triangular meshing of the formation surface of the present invention;

[0060] Figure 6 is a schematic diagram of the intersection line of the surface of the present invention;

[0061] Figure 7 is a diagram of the discretized calculation of the intersection line of the surface of the present invention;

[0062] Figure 8 is a local reconstruction diagram of the triangular mesh of the present invention;

[0063] Figure 9 is a diagram of the extraction result of the intersection line of the surface of the present invention. Detailed Embodiment

[0064] In order to make the purpose and advantages of the present invention clearer, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text only describes one or several specific implementation manners of the present invention, and does not strictly limit the scope of protection specifically claimed by the present invention.

[0065] As Figures 1-9As shown in the figure, a three-dimensional geological modeling method for steeply inclined strata includes the following steps:

[0066] Step 1: Establish a steeply inclined strata model that meets the strike and dip constraints;

[0067] The schematic diagram of the steeply inclined strata is as shown in Figure 1 , and Step 1 proposed by the present invention includes the following steps:

[0068] Step 101: Sort out the plane geological map and strata description data of the modeling target area, and extract the vector graph of the strike line of the steeply inclined strata in the modeling target area;

[0069] The plane geometric graph of the strike line of the steeply inclined strata in Step 101 can be obtained with the help of GIS or CAD software;

[0070] Step 102: According to the vector graph of the strike line, first perform equally spaced sampling on the strike line, and extract the set of plane coordinates of the strike line {P n} = {X s , Y s} as the basic data set for three-dimensional surface interpolation of the strata. The sampled points of the strike line extracted are as shown in Figure 2 ;

[0071] Here, the plane coordinate sampling interval can be determined according to the modeling accuracy and the range of the modeling target area. A smaller sampling interval will increase the later calculation amount.

[0072] Step 103: Perform curvature constraint on the strike data. This step is an optional step and can be selected according to user needs. It can be used for thinning of strike data points and control of layer surface smoothing.

[0073] Specifically, Step 103 includes the following steps:

[0074] The B-spline curve equation passing through the strike sampling points can be quickly obtained through data fitting, and is set as y = f(x). Starting from one end of the strike line as the starting point A (such as the A point in Figure 2 ), every three adjacent points are used to calculate the curvature, and traverse to the other end point B of the curve. For the curvature at the Pi(x0, y0) point shown in Figure 3 is:

[0075]

[0076] Through calculation by formula (1), the curvature set {κ1, κ2,..., κ n-2} of the strike curve is obtained.

[0077] Setting the value of r in formula (1) can perform appropriate threshold control on the curvature, aiming to avoid sharp changes in the strike of the created formation surface, and at the same time thin out the data points in the area with relatively small strike changes to reduce the computational amount in subsequent steps.

[0078] Step 104: Extract the stratigraphic data points of the modeling target formation from the borehole columnar diagram of the target area, establish an extended borehole dataset, and the formed dataset shall include the borehole name, orifice coordinates, formation name, layer depth measurement or elevation, as shown in Table 1 specifically;

[0079] Table 1 Example of borehole stratigraphic data representation

[0080]

[0081] Step 105: Establish a three-dimensional formation surface using the centerline method;

[0082] Step 105 includes the following steps:

[0083] Step 105a: Calculate the centerline top , Z bottom} according to the modeling depth range {Z

[0084] Step 105b: Combine the strike line plane coordinate set in Step 102, add the Z coordinate to the strike line coordinate set, and establish a three-dimensional coordinate set [X s , Y s , Z center of the formation centerline;

[0085] Step 106: Establish a three-dimensional formation surface line array using dip and dip angle constraints;

[0086] Step 106 includes the following steps:

[0087] Step 106a: Draw a line perpendicular to the tangent direction of the strike line at the point (x i , y i , z center ) of the three-dimensional coordinate points of the strike centerline and with an angle with the horizontal plane equal to the dip angle of the formation;

[0088] Step 106b: Obtain the direction vector of the line in Step 106a according to the definition of dip and dip angle α Thus, obtain the straight line equation of the dip line to form the line array of the formation surface, that is, the three-dimensional formation surface line array, as shown in Figure 4 specifically;

[0089] Step 107: Use the delaunay triangulation algorithm to triangulate the surface line array to form a triangular mesh, as shown in Figure 5 specifically;

[0090] Step 108: Based on the vertex dataset of the triangular mesh and combined with the borehole expansion dataset extracted in Step 104, form a control point dataset for the steeply inclined strata surface;

[0091] Due to the addition of the borehole expansion dataset, there may be problems of mutual deviation or conflict among the surface control points. Therefore, the grid curvature algorithm is used for surface smoothing. Among them, Step 108 includes the following steps:

[0092] For each vertex on the grid, take a neighborhood B around the point. The method of taking it is to satisfy all points whose distance to the point is less than or equal to a given distance d. For simplicity, all points within the sphere with the point as the center and radius d can be directly taken. Only the points and edges within the sphere are considered below. Define the following matrix:

[0093]

[0094] where |B| is the area of B; e is the edge of the grid in B; is the unit vector in the direction of e; ||e ∩ B|| is the length of e ∩ B, which is between 0 and |e|; β(e) is the angle between the two normal triangles with e as the common side.

[0095] Examine the eigenvalues and eigen-directions of the above matrix, The minimum eigenvalue and eigen-direction of can be used as the estimation formula for the normal vector of the grid surface at vertex p i The minimum eigenvalue and the maximum eigenvalue can be used as the estimation formulas for the principal curvatures κ1 and κ2. Then the mean curvature K H and the Gaussian curvature K G can be directly obtained from the principal curvatures according to the theory of differential geometry:

[0096]

[0097] Thus, the surface is smoothed using the mean curvature to generate a three-dimensional strata surface that not only conforms to the strata strike and dip laws but also satisfies the strata stratification positions exposed by the boreholes.

[0098] The above steps are also applicable to the three-dimensional modeling of the steeply inclined fault surface.

[0099] Step 2: Solve the intersection line of the unconformity surface and the steeply inclined strata surface to complete the three-dimensional geological modeling of the steeply inclined strata and the unconformity contact surface;

[0100] Step 2 includes the following steps:

[0101] Step 201: For the surfaces to be calculated, set them as the main and secondary surfaces respectively, where the main surface is the cutting surface and the secondary surface is the surface to be cut and trimmed, as Figure 6The unconformity shown is the main surface.

[0102] Specifically, step 201 includes the following steps:

[0103] Let the set of triangular mesh vertices of the main surface be f A (X, Y, Z), with the coordinate range being [X A , Y A , Z A , and the set of triangular mesh vertices of the secondary surface be f C (X, Y, Z), with the coordinate range being [X C , Y C , Z C . Through coordinate intersection operation, the entire coordinate set [X AC , Y AC , Z AC containing the intersection line L of surfaces A and C can be obtained; AC ;

[0104] Step 202: Perform uniform grid division on the coordinate set [X AC , Y AC , Z AC . Set the grid spacing to (ΔX AC , ΔY AC , ΔZ AC ). For simplicity, the grid spacings in the three-axis directions can be made the same. The number of grid cells in the X, Y, and Z coordinate axes directions are denoted as (m, n, p) respectively;

[0105] Step 203: Set the error threshold to Calculate that if it is less than the error threshold, the grid cells are considered to coincide;

[0106] Step 204: Substitute the coordinates of the grid cells into f (X, Y, Z) and f A (X, Y, Z) respectively. If C and and then this grid cell is on the intersection line of surfaces A and C and is marked;

[0107] Step 205: Traverse all grid cells to complete the marking of the grid cells on the surface intersection line, as shown in Figure 7 ;

[0108] Step 206: Use the triangle intersection algorithm to find the intersection points and add the intersection points to the triangular meshes of the two intersecting formation models respectively. If the intersection point is inside the triangle, add new coordinate points inside; if the intersection point is on the side of the triangle, add a new point at this point and divide this side. Specifically, as shown in Figure 8 ;

[0109] Step 207: Connect the vertices of the triangular mesh to construct new triangles, and use Delaunay triangulation to perform local reconstruction of the master and slave surfaces, as Figure 9 shown;

[0110] Step 208: Mark and delete the sub-regions of the surface according to the stratigraphic sequence and sedimentary relationship, so as to complete the 3D geological modeling of the steeply inclined strata and unconformity contacts.

[0111] In summary, the present invention proposes a convenient method for constructing a structural model for steeply inclined sedimentary strata. Compared with traditional 3D geological modeling software, it can significantly reduce the types and amounts of original modeling data, greatly reduce the modeling steps, shorten the modeling process, and effectively improve the modeling efficiency. The present invention has the following technical features:

[0112] The present invention uses strike and dip constraints for 3D interpolation of the formation surface, which preferably solves the problem of sparse or even missing borehole and formation stratification data. The present invention uses the strike line of the formation as the basic data for surface interpolation to achieve the purpose of expanding the interpolation sample set. At the same time, the dip angle is used as the normal constraint for 3D surface interpolation, and combined with borehole data to expand the set of layer control points, improving the local accuracy, which can preferably solve the problem of sparse modeling data and effectively improve the interpolation effect of sparse borehole data.

[0113] The present invention proposes an intersection line calculation method for unconformity surfaces applicable to steeply inclined strata, and realizes the solution algorithm for the intersection line of formation surfaces based on a grid method, without the need for partial derivatives and matrix operations, with extremely low algorithm complexity, having a natural discrete characteristic and being easy to program and implement.

[0114] The present invention introduces the idea of collision detection in computer-aided design, establishes bounding boxes for the formation models that may intersect, constructs octrees to screen the bounding boxes where potential intersecting triangles are located, then equally divides the space occupied by the bounding boxes into small cubes, establishes a triangle spatial index, and if the same cube contains triangles from two models, then find the intersection line of the two triangles. This method simplifies the solution of the intersection line of different surfaces to the intersection of intersecting triangles, can quickly exclude non-intersecting triangles, improves the operation efficiency, is applicable to the reconstruction of the contact relationship of steeply inclined formation models, and can meet the requirements of fault-cut sedimentary formation modeling.

[0115] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. The structures, devices, and operation methods not specifically described and explained in the present invention, unless otherwise specified and limited, are implemented according to the conventional means in the art.

Claims

1. A three-dimensional geological modeling method for steeply inclined strata, characterized in that: It includes the following steps: Step 1: Establish a steeply inclined strata model that conforms to the strike and dip constraints; The said Step 1 includes the following steps: Step 101: Extract the strike line vector graph of the steeply inclined strata in the modeling target area; Step 102: According to the trend line vector graph, perform equally spaced sampling on the trend line, and extract the set of planar coordinates of the trend line {P n} = {X s , Y s} as the basic data set for 3D surface interpolation of the strata; Step 104: Extract the stratified data points of the modeling target strata from the borehole columnar diagram of the target area and establish a borehole extended dataset; Step 105: Establish a three-dimensional strata surface using the centerline method; Step 106: Use the dip and inclination constraints to establish a three-dimensional layer line array of the strata; Step 107: Use the delaunay triangulation algorithm to triangulate the surface line array to form a triangular mesh; Step 108: Based on the vertex dataset of the triangular mesh and combined with the borehole extended dataset extracted in Step 104, form a control point dataset for the steeply inclined strata surface; Step 2: Solve the intersection line of the unconformity surface and the steeply inclined strata surface to complete the three-dimensional geological modeling of the steeply inclined strata and the unconformity contact surface; The said Step 2 includes the following steps: Step 201: Respectively set the surfaces to be calculated as the main and slave surfaces, where the main surface is the cutting surface and the slave surface is the surface to be cut and trimmed, and calculate to obtain the coordinate set [X AC , Y AC , Z AC ; The calculation coordinate set in the said Step 201 includes the following steps: Let the set of triangular mesh vertices of the main surface be f A (X, Y, Z), with the coordinate range being [X A , Y A , Z A . Let the set of triangular mesh vertices of the secondary surface be f C (X, Y, Z), with the coordinate range being [X C , Y C , Z C . By performing an intersection operation on the coordinates, the complete coordinate set [X AC , Y AC , Z AC , Z AC containing the intersection line L of surfaces A and C can be obtained; Step 202: Perform uniform grid division on the coordinate set [X AC , Y AC , Z AC . Set the grid spacing to (ΔX AC , ΔY AC , ΔZ AC ). The grid spacing in the three-axis directions is the same. Denote the number of grid cells in the X, Y, and Z coordinate axes as (m, n, p) respectively; Step 203: Set the error threshold to If the calculation result is less than the error threshold, it is considered that the grid cells coincide; Step 204: Substitute the coordinates of the grid cell into f separately for f A (X, Y, Z) and f C (X, Y, Z). If and then this grid cell is on the intersection line of surfaces A and C and is marked; Step 205: Traverse all grid cells to complete the marking of the grid cells of the surface intersection line; Step 206: Use the triangle intersection algorithm to find the intersection points, and add the intersection points to the triangulation networks of the two intersecting formation models respectively. If the intersection point is inside the triangle, add new coordinate points inside; if the intersection point is on the side of the triangle, add a new point at this point and divide this side. Step 207: Connect the vertices of the triangular mesh to construct new triangles and use the delaunay triangulation for local reconstruction of the main and secondary surfaces; Step 208: According to the stratigraphic sequence and sedimentary relationship, mark and delete the sub-regions of the surface to complete the three-dimensional geological modeling of the steeply inclined strata and the unconformity contact surface.

2. The three-dimensional geological modeling method for steeply inclined strata according to claim 1, characterized in that: The strike line vector graph in the said Step 101 is extracted according to the plane geological map and strata description data of the modeling target area.

3. The three-dimensional geological modeling method for steeply inclined strata according to claim 1, characterized in that: Between the said Step 101 and Step 104, it also includes: Step 103: Perform curvature constraint on the strike data.

4. The three-dimensional geological modeling method for steeply inclined strata according to claim 3, characterized in that: The said Step 103 includes the following steps: The B-spline curve equation passing through the trend sampling points is obtained by data fitting, denoted as y = f(x). Starting from one end of the trend line as the starting point A, every three adjacent points are used to calculate the curvature, and it is traversed to the other end point B of the curve. Let P i The curvature at the point (x0, y0) is: The curvature set {κ1, κ2,..., κ n-2} of the trend curve is obtained by calculating through formula (1).

5. The three-dimensional geological modeling method for steeply inclined strata according to claim 1, characterized in that: The borehole extended dataset in the said Step 104 includes the borehole name, orifice coordinates, strata name, layer depth measurement or altitude.

6. The three-dimensional geological modeling method for steeply inclined strata according to claim 1, characterized in that: The said Step 105 includes the following steps: Step 105a: Calculate the top center line according to the modeled depth range {Z bottom}, Step 105b: Combine the trend line plane coordinate set in Step 102, add the Z coordinate to the trend line coordinate set, and establish a three-dimensional coordinate set [X s , Y s , Z center of the formation center line.

7. A three-dimensional geological modeling method for steeply inclined strata according to claim 1, characterized in that: The said Step 108 includes the following steps: For each vertex on the grid, take a neighborhood B around the point, and the taking method is to satisfy all points whose distance to the point is less than or equal to the given distance d, and define the following matrix: where |B| is the area of B; e is the side of the grid in B; is the unit vector in the direction of e; ||e ∩ B|| is the length of e ∩ B, which is between 0 and |e|; β(e) is the angle between two normal triangles sharing e as a common side; Examine the eigenvalues and eigen-directions of the above matrix, The minimum eigenvalue and eigen-direction are used as the estimated formula for the normal vector of the mesh surface at vertex p i The minimum eigenvalue and the maximum eigenvalue are used as the estimated formulas for the principal curvatures κ1 and κ2. Then, the mean curvature K H and the Gaussian curvature K G are directly obtained from the principal curvatures according to the theory of differential geometry: Use the mean curvature to smooth the surface to generate a three-dimensional strata surface that not only conforms to the strike and dip laws of the strata but also satisfies the stratigraphic layered positions revealed by the boreholes.

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