A METHOD FOR ADAPTING AN UNSTRUCTURED MESH MODEL OF A GEOLOGICAL SUBSURFACE

1 . A method for adapting an unstructured mesh model of a geological subsurface obtained using measurements of said geological subsurface, to match it to a target, said unstructured mesh model comprising a first reference interface and a second reference interface, the first reference interface being associated with a first target interface, the second reference interface being associated with a second target interface, meshes of the unstructured mesh model having corners with coordinates (x, y, z) within said model and with parametric values (u,v,t) within said model, t representing a stratigraphic time for corners the method comprising:

for each corner between the first reference interface and the second reference interface—:

determining a vector at said corner, said vector is determined to maximize local variation of t, (u,v) being locally constant along said vector, values of parametric values (u, v, t) being determined based on neighboring corners for the determination of said vector;

determining a first distance between said corner and said first reference interface along said vector;

determining a second distance between said corner and said second reference interface along said vector;

determining a third distance between said corner and said first target interface along said vector;

determining a fourth distance between said corner and said second target interface along said vector; and

modifying the coordinates for said corner along said vector as a function of the first distance, the second distance, the third distance and the fourth distance

2 . The method according to claim 1 , wherein, a current coordinate system being defined along a line passing through said vector,

a first intersection between said line and said first reference interface having a coordinate c 1 in the current coordinate system,

a second intersection between said line and said second reference interface having a coordinate c 2 in the current coordinate system,

a third intersection between said line and said first target interface having a coordinate c 3 in the current coordinate system,

a fourth intersection between said line and said second target interface having a coordinate c 4 in the current coordinate system, said current corner having an initial coordinate c c in the current coordinate system, and

the modified coordinate of said current corner in the current coordinate system is a function of

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3 . The method according to claim 1 , further comprising, for each corner between the first reference interface and the second reference interface:

a second modification of the coordinates of said corner as a function of the current coordinates of said current corner and as a function of the current coordinates of distant corners that lie within a bounding box around the current corner.

4 . The method according to claim 3 , wherein, the coordinates of the corners being expressed by a plurality of components, the second modification of the coordinates of said corner includes calculating a median filter or an average of the coordinates of said current corner along at least one component of the coordinates of said distant corners along the at least one component.

5 . The method according to claim 3 , wherein the bounding box is a function of a distance from said current corner to a fault in said model.

6 . The method according to claim 3 , wherein the bounding box is a function of an anisotropic direction in said model.

7 . The method according to claim 6 , wherein the anisotropic direction is parallel to a line passing through said current corner and perpendicular to a fault in said model.

8 . The method according to claim 1 , wherein, the coordinates of the corners being expressed by a plurality of components, the distance between a current corner and a modified current corner, along at least one coordinate component, is less than a threshold value.

9 . The method according to claim 1 , wherein, the model includes at least one fault, the method further comprising:

identifying at least one corner having a distance to the at least one fault that is less than a predetermined influence distance; and

modifying the coordinates of the corner having a distance to the at least one fault that is less than the predetermined influence distance, as a function of modifications determined for a plurality of points having a distance to the at least one fault that is greater than the predetermined influence distance and part of a common interface with the corner having a distance to the at least one fault that is less than the predetermined influence distance.

10 . The method according to claim 9 , wherein the modifying the coordinates of the corner having a distance to the at least one fault that is less than the predetermined influence distance includes calculating a weighted average.

11 . The method according to claim 9 , wherein the modifying the coordinates of the corner having a distance to the at least one fault that is less than the predetermined influence distance includes a regression.

12 . A device for adapting an unstructured mesh model of a geological subsurface obtained using measurements of said geological subsurface, to match it to a target, said unstructured mesh model comprising a first reference interface and a second reference interface, the first reference interface being associated with a first target interface, the second reference interface being associated with a second target interface, meshes of the unstructured mesh model having corners with coordinates (x, y, z) within said model and with parametric values (u,v,t) within said model, t representing a stratigraphic time for corners the device comprising:

for each corner between the first reference interface and the second reference interface-:

a circuit configured to determine a vector at said corner, said vector determined to maximize local variation of t, (u,v) being locally constant along said vector, values of parametric values (u, v, t) being determined based on neighboring corners for the determination of said vector;

a circuit configured to determine a first distance between said corner and said first reference interface along said vector;

a circuit configured to determine a second distance between said corner and said second reference interface along said vector;

a circuit configured to determine a third distance between said corner and said first target interface along said vector;

a circuit configured to determine a fourth distance between said corner and said second target interface along said vector;

a circuit configured to modify the coordinates for said corner along said vector as a function of the first distance, the second distance, the third distance and the fourth distance; and

an interface configured to output a modified model based on the modification of the coordinates for said corner.

13 . A non-transitory computer program product comprising instructions, which, when executed by a processor, cause the processor to implement the method according to claim 1 .