Method for modelling a surface and device for implementing same

• US 5,465,323 A
• Filed: 05/20/1991
• Issued: 11/07/1995
• Est. Priority Date: 09/20/1989
• Status: Expired due to Term

• Current Assignee: Cggveritas Services SA (CGG), Societe Nationale Elf Aquitaine (Cook Composites and Polymers), Total Compagnie Francaise Des Petroles
• Original Assignee: Association Scientifique Pour La Geologie et de SES Applications, Compagnie Generale De Geophysique, Total Compagnie Francaise Des Petroles, Societe National Elf Aquitaine (Totalenergies Se)
• Inventors: Mallet, Jean-Laurent
• Primary Examiner(s): Zimmerman, Mark K.
• Application Number:
  US07/689,044
• Time in Patent Office: 1,632 Days
• Field of Search: 395/119, 395/120, 395/123, 395/141, 395/142, 364/413.17, 364/421
• US Class Current: 345/423
• CPC Class Codes: A61F 2/30942 for designing or making customized prostheses, e.g. using templates, CT or NMR scans, finite-element analysis or CAD-CAM techniques
• CPC Class Codes: A61F 2002/30943 using mathematical models
• CPC Class Codes: A61F 2002/30952 using CAD-CAM techniques or NC-techniques
• CPC Class Codes: A61F 2240/002 Designing or making customized prostheses
• CPC Class Codes: G01V 1/282 Application of seismic models, synthetic seismograms
• CPC Class Codes: G01V 2210/66 Subsurface modeling
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation

Abstract

A method for obtaining a model of a surface including the steps of obtaining measurements of geometrical data concerning specific points on the surface, making a grid of the surface, with the grid passing through said points, memorizing, at an address which is specific to each node of the grid, the coordinates of the node, the number of satellites of the node, information for access to the addresses of said satellites and thereafter to information which relates to them, and geometrical data which may be associated with said node; for each node, defining a local roughness index obtained from a weighted sum of the current coordinates of the node and its satellites, defining the sum of an overall roughness index representing the sum of all the local roughness indices, and of an overall index of the infringement of said geometrical data, iteratively adjusting the coordinates of indefinite nodes, by using at each adjustment the sum of a weighted combination of current node neighbor coordinates and of a combination of geometrical data associated with the node, in order to minimize said sum, and creating a model of the surface on the basis of the adjusted coordinates.

Claims

1. A process for modeling a surface representing an interface between two areas with different properties in a three-dimensional body, comprising the steps of:

measuring to obtain a set of geometrical data, from said interface of said three-dimensional body, relating to the surface and associated with respective points on said surface;

meshing the surface so that all said points are a subset of nodes of a mesh;

storing at a specific memory address for each node of the mesh, the following data;

first, second, and third coordinates,

a number of satellite nodes,

satellite node address data providing access to specific coordinates of said satellite nodes and consequently to satellite node related data relating thereto, and

geometrical data associated with said each node of the mesh;

for each node of the mesh, defining a local roughness index derived from a weighted sum of the coordinates of the node and of its satellites;

defining a global roughness index obtained by summing the local roughness indices associated with the nodes, and a global violation index of said geometrical data, to thereby generate a sum of said global roughness index and said global violation index;

fitting fitted coordinates of each node processed by an iterative method in which for each step of an iteration there is added a weighted combination of the coordinates of the node and of the satellites of said node and a combination of the geometrical data associated with said node, to thereby minimize said sum of the global roughness index and the global violation index; and

creating a representation of the surface from the fitted coordinates of each node.

2. A process according to claim 1, wherein:

the surface is meshed using triangles.

3. A process according to claim 1 wherein:

the fitting step comprises three separate sub-steps respectively using the first, second, and third coordinates of the nodes and the coordinates of the satellite nodes corresponding thereto, respectively.

4. A process according to claim 1, wherein:

the geometrical data includes vector data between two given nodes.

5. A process according to claim 1, wherein:

the geometrical data includes data of a vector normal to the surface to be modeled.

6. A process according to any one of claims 4 to 5, wherein:

at least one geometrical datum is associated with a coefficient representing a certainty factor by which said at least one datum is known, the global violation index is a function of said certainty factors.

7. A process according to claim 1, further comprising the steps of measuring properties of the three-dimensional body in a region of at least one node of the mesh and storing the measured properties at addresses specific to the at least one node so as to obtain complementary data of the three-dimensional body.

8. A process according to claim 1, wherein:

for each local roughness index, a ratio between a first and a second weight of a corresponding node equals a negative of the number of satellite nodes.

9. A process according to claim 8, wherein:

said weighted combination uses substantially the same weighting as the ratio.

10. A process according to claim 1, wherein:

the summing of the local roughness indices is a weighted summing.

11. A process according to claim 10, wherein:

said weighted combination uses the weighting associated with the local roughness indices.

12. A process according to claim 1, wherein:

the three-dimensional body is a geological formation.

13. A process according to claim 1, wherein:

the surface represents variations of a property of a two-dimensional body in a vicinity of a plane intersecting said body, said property being represented by a remaining dimension, and a representation of the surface is used to optimize visualization of underground resources of said three-dimensional body, said three dimensional body being a geological formation.

14. A process according to claim 1, wherein:

the representation of the surface is a graphical representation on a flat medium.

15. A method according to claim 1, wherein:

the representation of the surface is a three-dimensional model.

16. A device for modeling a surface representing an interface between two areas with different properties in a three-dimensional body, comprising:

means for measuring to obtain a set of geometrical data, from said interface of said three-dimensional body, relating to the surface and associated with respective points on said surface;

means for meshing the surface so that all said points are a subset of nodes of a mesh;

means for storing at a specific memory address for each node of the mesh, the following data;

first, second, and third coordinates,

a number of satellite nodes,

satellite node address data providing access to specific coordinates of said satellite nodes and consequently to satellite node related data relating thereto, and

geometrical data associated with said each node of the mesh;

calculation means for fitting fitted coordinates of each node processed by an iterative method in which for each step of an iteration there is added a weighted combination of the coordinates of the node and of the satellites of said node and a combination of the geometrical data associated with said node, to thereby minimize a sum of a global roughness index obtained by summing local roughness indices associated with the nodes, each local roughness index derived from a weighted sum of the coordinates of the node and the coordinates of its satellites, and of a global violation index of said geometrical data; and

means for creating a representation of the surface from the fitted coordinates of each node.