A 3D printing digital model generation method

Abstract

The application discloses a 3D printing digital model generation method, and belongs to the field of oil and gas reservoir development. The method is based on a commonly used GRDECL format corner point grid model of a reservoir geological model, and proposes a fracture-vug type reservoir geological model grid information automatic extraction, three-dimensional profile construction and three-dimensional profile optimization algorithm. Without model coarsening and similarity analysis, the automatic high-precision conversion from the corner point grid model to the STL format 3D printing digital model can be realized, and the convenience and accuracy of the fracture-vug type reservoir space physical model printing are solved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas reservoir development, and specifically relates to a method for generating 3D printed digital models. Background Technology

[0002] Fractured-vuggy reservoirs exhibit complex multiphase flow coupling, involving both porous media seepage and large-space pipe flow. To elucidate the flow patterns of multiphase fluids in fractured-vuggy carbonate reservoirs, physical simulation methods are commonly used in research. [1-4] Due to the complexity of the reservoir space and the special pore structure characteristics of fractured-vuggy media, conventional sand filling methods, cementing methods, and etching methods (chemical etching and laser engraving) cannot be applied to the fabrication of physical models of fractured-vuggy reservoirs with multiple pore types, thus limiting the application of physical simulation methods in studying the transport and flow mechanisms of fractured-vuggy porous media.

[0003] In recent years, 3D printing technology has developed rapidly, demonstrating significant advantages in its application to fractured reservoir model experiments. Compared to traditional physical model preparation methods such as using acrylic glass, 3D printed physical models can be computer-controlled to print the pore distribution of realistic fractured reservoirs, precisely matching their actual size and shape. The surfaces of the fractures and cavities closely resemble the actual conditions. [5-7] .

[0004] The STL file format is the standard file format for 3D printing digital models. Almost all rapid prototyping machines can accept STL file formats for printing. It was developed in 1988 by Charles W. Hull, the founder of 3D Systems. [8] It is the de facto standard file format for 3D printing.

[0005] Although the STL file format is well-defined and supported by many computer-aided design (CAD) software programs, the preparation of 3D printed physical models currently lacks a reliable source of digital model parameters. In oilfield development, geological models constructed using commercial software such as Petrel, RMS, and GOCAD are the primary data volume type reflecting the characteristics of fractured-vuggy reservoirs. These geological models are generally constructed using hexahedral corner meshes in the GRDECL format, while 3D printed digital models are constructed using the triangle-based STL format. There are significant differences between the two in both geometric structure and file format. Currently, the corner mesh data of fractured-vuggy reservoir geological models cannot be directly recognized by 3D printers, and there is no readily available automated method to easily convert them to STL format, causing considerable inconvenience to the 3D printing of fractured-vuggy physical models.

[0006] References: [1] Li Jianfeng, Zhao Qun, Hao Shuling, et al. Physical simulation study of fracture-vuggy system in carbonate reservoir of Tahe Oilfield [J]. Petroleum Geophysical Prospecting, 2005, 44(5): 428-432. [2] Xu Chuanqi, Fu Meilong, Qin Tianbao, et al. Visual model experiment on water production law of fractured-vuggy carbonate reservoirs[J]. Petroleum Drilling and Production Technology, 2020, 42(2): 195-200. [3] Liu Xueli, Zheng Xiaojie, Tan Tao, et al. Experimental study on CO2 flooding mechanism of Tahe strong bottom water sandstone reservoir [J]. Oil & Gas Reservoir Evaluation and Development, 2020, 10(06): 115-120. [4] Wang Diansheng, Yao Jun. Experimental and numerical simulation study on flow mechanism of slotted media [D]. China University of Petroleum, 2009. [5] Yu, Miao. Study on 3D printing technology and distribution law of residual oil in fractured-vuggy reservoirs [J]. China University of Petroleum (East China), 2017. [6] Wang Chaoqi. Research on waterflooding law and enhanced oil recovery strategies in fractured-vuggy reservoirs [J]. China University of Petroleum (East China), 2018. [7] Dai Caili, Fang Jichao, Jiao Baolei, et al. Research progress on enhanced oil recovery in fractured-vuggy carbonate reservoirs in China [J]. Journal of China University of Petroleum (Natural Science Edition), 2018, 42(6): 67-78. [8] Hull C W. Apparatus for production of three-dimensional objects by stereolithography[J]. United States Patent, Appl., No. 638905, Filed,1984. Summary of the Invention To address the challenge of automatically converting GRDECL format corner mesh models of fractured-vuggy reservoirs into STL format 3D printing digital models, this invention provides a method for generating 3D printing digital models. This method analyzes the data structure and file format of fractured-vuggy reservoir geological models and 3D printing digital models, and based on key algorithms such as fracture-vuggy model extraction, 3D contour construction and optimization, it automatically converts corner mesh models into 3D printing models.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: First, a method for generating 3D printed digital models is provided, the method comprising the following steps: (1) Construct a corner grid and parse the grid's attribute information; (2) Extract the fracture-cavity system from the geological model and find similar connected regions; (3) Construction and triangulation of the three-dimensional contour of the slit hole model; (4) Optimization of the three-dimensional contour of the slit model; (5) Generation of 3D printed digital models.

[0008] Furthermore, the corner mesh file mentioned in step (1) includes SPECGRID, COORD, ZCORN, and ACTNUM, and the attribute information includes mesh validity, partition information, porosity, and permeability.

[0009] Furthermore, the grid validity refers to the fact that grids that are not reservoirs or have no effective porosity are invalid grids.

[0010] Furthermore, the zoning information refers to the zoning information of the matrix, fissures, or caves. The zoning information is denoted as ZONE, with the matrix denoted as ZONE=1, fissures as ZONE=2, and caves as ZONE=3.

[0011] In a specific implementation, step (2) involves extracting the geological model's fracture-cavity system based on the corner grid information read and parsed in step (1) and the fracture-cavity partitioning attribute (ZONE) of the geological model, and searching for similar connected regions to extract the fractures and cavities in the geological grid respectively.

[0012] Furthermore, the similar connected regions mentioned in step (2) are caves or fissures, and the method for constructing similar connected regions of the caves includes the following steps: ① Mark the state parameters of all grids as 0, denoted as ; ②With any grid Starting from the empty set, establish an empty set. Mark the grid The state parameter is 1, denoted as and grid Add to collection middle; ③ Define the adjacent grid criteria , grid and The necessary and sufficient condition for adjacency is: i1, j1, k1 are The 3D mesh numbers, i2, j2, k2 are The three-dimensional mesh number; ④ Searching for the current grid The ZONE=3 values ​​are the same and Adjacent grids, adjacent grids meet the criteria , forming a set Mark these grids and add it to the collection middle; ⑤ Traversal Repeat steps ③ and ④ for all grids until... If empty, meaning no adjacent grids of the same type can be found, the result is... That is, a connected region of the same type; ⑥ Traverse all grids with a state parameter of 0 until all grids are exhausted. To obtain all connected regions of the same type in the cave. ; The method for constructing similar connected regions of the crack includes the following steps: applying the criterion in step ③... Change to: The remaining steps are consistent with the method for constructing similar connected regions in a cave, thus obtaining all similar connected regions of the fissure. .

[0013] Further, step (3) includes the following steps: generating three-dimensional boundary surfaces of the same type of connected regions obtained in step (2) to construct the three-dimensional contours of each slot system.

[0014] Furthermore, the steps for generating the three-dimensional boundary surface of the slot system include marking the six faces of the cubic mesh, obtaining the coordinates of the eight vertices of the mesh, finding the boundary face of the mesh, obtaining the coordinates of the four vertices of the boundary face, triangulating the boundary face, and numbering the boundary face triangles.

[0015] Furthermore, the optimization method described in step (4) includes the following steps: triangle subdivision, marking new and old vertices, constructing new vertex adjustment functions, and constructing old vertex adjustment functions.

[0016] Furthermore, the process of generating the 3D printed digital model in step (5) involves outputting the three-dimensional contour of the optimized slit model in step (4) into a 3D printed digital model format file.

[0017] Finally, the application of the above-described generation method in constructing reservoir geological models is presented.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention realizes the direct output of reservoir geological models represented by GRDECL format corner mesh to 3D printers, providing a convenient technical method for expanding the application field of reservoir geological models and improving the realism and accuracy of indoor fracture and cavity physical models; (2) The data format conversion method formed by the present invention can be used to convert any reservoir geological model into a 3D printing format, supporting the development of indoor physical model processing and preparation technology in the field of reservoir development. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the corner grid geometry. Figure 2 This is a schematic diagram of the discontinuity error in the equivalent mesh of the crack. Figure 3 A schematic diagram showing the markings on the six faces of the mesh; Figure 4 This is a schematic diagram of the boundary surface triangulation. Figure 5 A geometric topology diagram using vertex + index method; Figure 6 This is a schematic diagram of triangle subdivision; Figure 7 A schematic diagram of the function adjustment for the new vertex; Figure 8 A schematic diagram of the old vertex adjustment function; Figure 9 Grid diagram of corner points of fractured reservoir; Figure 10 Extraction map of the cave model grid; Figure 11 Extracting the crack mesh map; Figure 12 Construct a 3D outline of the cave model; Figure 13 Construct a 3D contour map of the crack model; Figure 14 An optimized 3D outline diagram of the karst cave model; Figure 15 An optimized 3D contour diagram of the crack model; Figure 16 This is an image of a 3D printed digital model (STL Viewer). Detailed Implementation

[0020] The following description of the embodiments is merely to aid in understanding the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of the claims. The following description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not limited to the embodiments shown herein, but can be applied to a wider scope consistent with the principles and novel features disclosed herein. While any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of the present invention, preferred methods and materials are listed herein.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] Example The main method of this invention is to automatically generate an STL format 3D printing digital model based on the GRDECL format corner mesh model of fractured-vuggy reservoirs. The detailed method is as follows: 1. Corner mesh file parsing and reading / writing First, the geometric information data of the corner mesh file needs to be parsed. The corner mesh file consists of main parts such as SPECGRID, COORD, ZCORN, and ACTNUM. SPECGRID NI N2 N3 / COORD X11 Y11 Z11 X12 Y12 Z12… XM1 YM1 ZM1 XM2 YM2 ZM2 / ZCORN Z11 Z12 Z13 Z14 Z15 Z16 Z17 Z18… ZN1 ZN2 ZN1 ZN4 ZN5 ZN6 ZN7 ZN8 / ACTNUM A1 A2 … AN / ZONE Z1 Z2 … ZN / PORP1 V11 V12 … V1N / PORP2 V21 V22 … V2N / PROPN VN1 VN2 … VNN / Assume the reservoir has N1, N2, and N3 grid numbers in the X, Y, and Z directions, respectively. To construct the corner grid, pillars need to be generated along the depth direction. Two points determine a straight line, and each point corresponds to three coordinate values; therefore, defining one pillar requires six data points.

[0023] Once the supports for the corner mesh are fixed, the exact location of the mesh is still uncertain. At this point, another parameter is needed: the Z-coordinates of the eight corner points. Because the corner points can only move along the defined supports, knowing the coordinates of a point in any direction allows us to calculate its position on the supports—the three-dimensional coordinates of the corner point. Since the contact surfaces of adjacent corner meshes may not perfectly overlap, each corner point of each mesh needs to be defined individually. For a hexahedral mesh, each mesh has eight corner points, and each corner point requires a coordinate value for location, resulting in a total of 8 × N1 × N2 × N3 Z-coordinates. See the corner mesh geometry below. Figure 1 .

[0024] After parsing the corner mesh geometry, the next step is to parse the mesh attribute information (see Table 1).

[0025] Table 1

[0026] 2. Extraction of seam and hole models from mesh models (Key Algorithm 1) This step, based on the corner grid information read and parsed in step 1, extracts the fracture-cavity system of the geological model according to the fracture-cavity zone attribute (ZONE), and searches for similar connected regions to extract fractures and cavities from the geological grid separately. The method for constructing similar connected regions is as follows (taking cavities as an example): ① Mark the state parameters of all grids as 0, denoted as ; ②With any grid Starting from the empty set, establish an empty set. Mark the grid The state parameter is 1, denoted as and grid Add to collection middle; ③ Define the adjacent grid criteria , grid and The necessary and sufficient condition for adjacency is: i1, j1, k1 are The 3D mesh numbers, i2, j2, k2 are The three-dimensional mesh number; ④ Searching for the current grid The ZONE=3 values ​​are the same and Adjacent grids, adjacent grids meet the criteria , forming a set Mark these grids and add it to the collection middle; ⑤ Traversal Repeat steps ③ and ④ for all grids until... If empty, meaning no adjacent grids of the same type can be found, the result is... That is, a connected region of the same type; ⑥ Traverse all grids with a state parameter of 0 until all grids are exhausted. To obtain all connected regions of the same type in the cave. ; The steps for finding similar connected regions of cracks are the same as above. See the schematic diagram of the equivalent mesh discontinuity error of cracks. Figure 2 In addition to handling local discontinuities in crack modeling, the criterion in ③ is used. The necessary and sufficient condition is changed to: This yields all connected regions of the same type from the cracks. .

[0027] 3. Construction and triangulation of the 3D contour of the slit model (key algorithm 2) This step generates a three-dimensional boundary surface for the fracture-cavity system based on the connected regions of the same type of cracks and caves obtained in step 2, in order to construct the three-dimensional contour of each fracture-cavity system.

[0028] The method for constructing the 3D contour of a cave (or fissure) is as follows: ①According to the grid Orientation, marking the six faces of each grid as , , , , and ,like Figure 3 As shown, their directional adjacent grids are defined as follows: ; ② Obtain the mesh The coordinates of the 8 points: First, determine the Z-coordinate number of the vertex:

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] Next, determine the Z-coordinate:

[0037] Third, determine the column number:

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] Fourth, determine the XY coordinates:

[0046]

[0047] In the above formula, NI, NJ, and NK are the number of grids along the I, J, and K axes, respectively.

[0048] ③For any Find the boundary surfaces of all the grids, i.e., the surfaces whose adjacent grids in the corresponding directions do not belong to the boundary surface. All faces, recorded as

[0049] ④ For any In step ②, obtain the coordinates of its four vertices and number them sequentially, denoted as . And triangulate it, that is, divide it into two triangles, the face can be represented as and (like Figure 4(As shown), note that the shorter diagonal should be chosen as the common side of the triangle; ⑤ Sort all the vertices of the boundary triangles in this order, according to Figure 5 The methods are numbered sequentially, and the vertex numbers of triangles in ④ are changed to the new numbers.

[0050] 4. Optimization of the 3D contour of the seam model (Key Algorithm 3) This step optimizes the 3D contour obtained in step 3, as follows: ① Triangle subdivision: Connect the midpoints of the three sides of a triangle to divide it into four triangles, such as... Figure 6 As shown; ② Mark the old and new vertices, that is, divide the triangle into the old vertices (i.e., the original three vertices). And the new vertices (i.e., the three points in the middle of the three edges). ; ③ For any new vertex Define its adjustment coordinates See the diagram of the new vertex adjustment function. Figure 7 Its value is related to its surrounding neighboring vertices:

[0051] in, Indicates the old vertex number. This indicates the number of times a vertex is used by a triangle (as a vertex of a triangle), as shown in the figure. The point, its adjusted coordinates are: .

[0052] ④ For any old vertex Define its adjustment coordinates See the diagram of the old vertex adjustment function. Figure 8 Its value is related to the number of times the point is shared by the surrounding triangles:

[0053] in

[0054] 5. Generation of 3D Printed Digital Models In this step, the optimized three-dimensional contour of the fractured-vuggy reservoir model obtained in step 4 is output as a 3D printing digital model format file.

[0055] An STL file provides the geometric information of a triangular facet line by line, with each line beginning with one or two keywords. The unit of information for a triangular facet in an STL file is a triangular facet with a vector direction; an STL 3D model is composed of a series of such triangular facets. The first line of the entire STL file specifies the file path and filename. In an STL file, each facet consists of 7 lines of data. `facetnormal` is the coordinate of the normal vector pointing outwards from the solid, and `outerloop` indicates that the following 3 lines contain the coordinates of the three vertices of the facet, arranged counter-clockwise along the normal vector pointing outwards from the solid. The STL file information is as follows: UINT8

[80] – Header UINT32 – Number of triangles foreach triangle REAL32[3] – Normal vector REAL32[3] – Vertex 1 REAL32[3] – Vertex 2 REAL32[3] – Vertex 3 UINT16 – Attribute byte count End Experimental Example Figure 9 This is a grid of corner points of a fractured reservoir provided for an embodiment, where the dark part represents caves and the light part represents fractures. Figure 10-16 The method described in the embodiments is obtained, wherein: step 2 yields... Figure 10-11 The mesh extraction image is obtained in step 3. Figure 12-13 The 3D contour drawing of the model is obtained in step 4. Figure 14-15 The optimized 3D contour map of the model is obtained in step 5. Figure 16 A 3D printed digital model (STL Viewer) image.

[0056] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for generating a 3D printed digital model, characterized in that, The generation method includes the following steps: (1) Construct a corner grid and parse the grid's attribute information; The corner mesh files mentioned in step (1) include SPECGRID, COORD, ZCORN, and ACTNUM, and the attribute information includes mesh validity, partition information, porosity, and permeability. The zoning information refers to the zoning information of the matrix, fissures, or caverns; The partition information is denoted as ZONE, the matrix is ​​denoted as ZONE=1, the fissure is denoted as ZONE=2, and the cave is denoted as ZONE=3; (2) Extract the fracture-cavity system from the geological model and find similar connected regions; The similar connected regions mentioned in step (2) are caves or fissures. The method for constructing similar connected regions of the caves includes the following steps: ① Mark the state parameters of all grids as 0, denoted as ; ②With any grid Starting from the empty set, establish an empty set. Mark the grid The state parameter is 1, denoted as and grid Add to collection middle; ③ Define the adjacent grid criteria , grid and The necessary and sufficient condition for adjacency is: i1, j1, k1 are The 3D mesh numbers, i2, j2, k2 are The three-dimensional mesh number; ④ Searching for the current grid The ZONE=3 values ​​are the same and Adjacent grids, adjacent grids meet the criteria , forming a set Mark these grids and add it to the collection middle; ⑤ Traversal Repeat steps ③ and ④ for all grids until... If empty, meaning no adjacent grids of the same type can be found, the result is... That is, a connected region of the same type; ⑥ Traverse all grids with a state parameter of 0 until all grids are exhausted. To obtain all connected regions of the same type in the cave. ; The method for constructing similar connected regions of the crack includes the following steps: applying the criterion in step ③... Change to: The remaining steps are consistent with the method for constructing similar connected regions in a cave, thus obtaining all similar connected regions of the fissure. ; (3) Construction and triangulation of the three-dimensional contour of the slit hole model; Step (3) includes the following steps: generating three-dimensional boundary surfaces of the same type of connected regions obtained in step (2) to construct the three-dimensional contours of each slot system; The steps for generating the three-dimensional boundary surface of the slot system include marking the six faces of the cubic mesh, obtaining the coordinates of the eight vertices of the mesh, finding the boundary face of the mesh, obtaining the coordinates of the four vertices of the boundary face, triangulating the boundary face, and numbering the boundary face triangles. (4) Optimization of the three-dimensional contour of the slit model; The optimization method described in step (4) includes the following steps: triangle subdivision, marking new and old vertices, constructing new vertex adjustment functions, and constructing old vertex adjustment functions; (5) Generation of 3D printed digital models.

2. The generation method according to claim 1, characterized in that, The process of generating the 3D printed digital model in step (5) is to output the three-dimensional contour of the optimized slit model in step (4) into a 3D printed digital model format file.

3. The application of the generation method according to any one of claims 1-2 in constructing reservoir geological models.

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