Inversion method

Patent metadata

Field	Value
Publication number	US-2016334532-A1
Application number	US-201415110352-A
Country	US
Kind code	A1
Filing date	Jan 8, 2014
Priority date	Jan 8, 2014
Publication date	Nov 17, 2016
Grant date	—

Abstract

A method of estimating electromagnetic parameters of a geological structure, comprising: providing controlled source electromagnetic, CSEM, data of the structure, calculating a numerical model representing electromagnetic parameters of the structure and generating simulated CSEM data, discretising the numerical model based on prior knowledge of the structure, defining a functional for minimising the distance between said simulated CSEM data and said CSEM data, wherein the functional comprises a regularisation term which depends on prior knowledge of said structure.

First claim

1 . A method of estimating electromagnetic parameters of a geological structure, comprising the steps of:
providing controlled source electromagnetic, CSEM, data of the structure; calculating a numerical model representing electromagnetic parameters of the structure and generating simulated CSEM data; discretising the numerical model based on prior knowledge of the structure; and defining a functional for minimising the distance between said simulated CSEM data and said CSEM data, wherein the functional comprises a regularisation term which depends on prior knowledge of said structure.

2 . The method of claim 1 , wherein the electromagnetic parameters are the conductivity of the geological structure at a plurality of locations of the structure.

3 . The method of claim 1 , wherein the regularisation term has a strength which depends on the location of the structure.

4 . The method of claim 1 , wherein the regularisation term comprises a plurality of weights corresponding to a plurality of geological locations, wherein some of the locations are defined with more confidence than other locations, and wherein locations defined with more confidence are assigned higher weights than locations with less confidence.

5 . The method of claim 1 , wherein the regularisation term comprises a plurality of weights corresponding to a plurality of geological locations, and wherein the weights which are assigned to locations with horizons passing through them are lower than weights assigned to locations without horizons passing through them.

6 . The method of claim 1 , wherein said prior knowledge comprises seismic survey data.

7 . A method of estimating electromagnetic parameters of a geological structure, comprising the steps of:
providing controlled source electromagnetic, CSEM, data of the structure; calculating a numerical model representing parameters of the structure and generating simulated CSEM data; discretising the numerical model based on prior knowledge of the structure; and defining a functional for minimising the distance between said simulated CSEM data and said CSEM data, wherein the functional comprises terms correlating neighbouring geological locations in dependence on prior knowledge of said structure.

8 . The method of claim 7 , wherein said correlating depends on the presence of a structural gradient estimated from prior knowledge of said structure.

9 . The method of claim 7 , further comprising defining a first spatial direction in the tangential plane of said structure and a second spatial direction perpendicular to the tangential plane of said structure

10 . The method of claim 9 , wherein a high correlation is assigned to neighbouring locations in the first spatial direction and wherein a low correlation is assigned to neighbouring locations in the second spatial direction.

11 . The method of claim 7 , wherein said prior knowledge comprises seismic survey data.

12 . The method of claim 7 , wherein the electromagnetic parameters are the conductivity of the geological structure at a plurality of locations of the structure.

13 . The method of claim 8 , wherein the first and second spatial directions are chosen according to said step of discretising the numerical model.

14 . A computer device comprising:
a receiver for receiving controlled source electromagnetic, CSEM, data of a geological structure; and a processor arranged to carry out the method of claim 1 .

15 . A computer program comprising non-transitory computer readable code which, when run on a computer device, causes the computer device to behave as the computer device according to claim 14 .

16 . A computer program product comprising a non-transitory computer readable medium and the computer program according to claim 15 , wherein the computer program is stored on the non-transitory computer readable medium.

Assignees

• Statoil Petroleum As

Inventors

• Wiik Torgeir
• Dischler Eirik Øverland
• Nordskag Janniche Iren
• Nguyen Anh Kiet

Classifications

• G01V2003/086

  Processing · CPC title

• G01V3/083 Primary

  Controlled source electromagnetic [CSEM] surveying · CPC title