Statoil Petroleum As

Equinor Energy As

Sintef Petroleumsforskning

Emmanuel Causse

Janniche Iren Nordskag

Anh Kiet Nguyen

Ketil Hokstad

Torgeir Wiik

Frank Agnar Maaø

Frank Agnar Maao

A method of obtaining a model of a sub-surface region, the model comprising a three dimensional matrix of sub-surface material property values. The method comprises providing a first approximation of said model, and performing simulations using the model to generate (i) a reference upgoing energy wave data set d, where the acquisition parameters used in the simulation are a set of known acquisition parameters, and (ii) a plurality of perturbed upgoing energy wave data sets dwhere the acquisition parameters are obtained by randomly perturbing said set of known acquisition parameters. The method further comprises forming a matrix D, the columns of which are the differences d&#x2212;dbetween the ith perturbed data set and the reference data set, applying an analysis to the matrix D to describe the matrix using a set of vectors, and selecting the most important vectors from said set of vectors to obtain a subset of vectors that describe said matrix D to an approximation. An iterative procedure is performed to improve said first approximation of said model, or a further approximation model, wherein, at each step of the procedure, a model update &#x394;m is determined, the model update being that model update that minimises a measure of the data misfit between said upgoing energy wave data set dand a data set simulated using the updated model, said measure using said subset of vectors to account for uncertainty in the upgoing energy wave data set d.

Providing for uncertainty in non-linear inversions of geophysical data

A method of solving a geophysical inverse problem for estimating a physical parameter, the method comprising providing a model vector representing the physical parameter, transforming the model vector by a first operator to provide a first transformed model vector, solve the inverse problem for the first transformed model vector to provide a first solution, transforming the model vector by a second operator to produce a second transformed model vector, solve the inverse problem for the second transformed model vector to provide a second solution, calculating a weighted sum of the first solution and the second solution.

Efficient solutions of inverse problems

A method of estimating a set of physical parameters, the method comprising iteratively inverting an equation to minimise an error between simulated data and measured data and to provide an estimated set of physical parameters, wherein said iteratively inverting comprises at least a first inversion step and a second inversion step and wherein the simulated data depend on a model vector representing the set of physical parameters, applying a compression operator to the model vector representing the set of physical parameters to reduce the number of free variables and to produce a compressed model vector and varying the compression operator between the first inversion step and the second inversion step.

Model compression

A method of constructing a basis of functions intended for the building of approximations of one-way or two-way seismic traveltime versus offset functions. The method is characterized by the combination of the following steps of (a) creating a distribution of reference one-way or two-way traveltime versus offset functions by traveltime modelling in a set of velocity models representing possible velocity distributions, (b) obtaining new reference functions by modifying these reference traveltime functions by applying an operator to them, (c) selecting a set of discrete offsets to make these new reference functions discrete, (d) arranging these discrete functions in columns to form a matrix, (e) applying a singular value decomposition to this matrix, with singular values sorted in decreasing order, to express its columns as linear combinations of the columns of an orthogonal matrix, and (f) building the basis functions by interpolating the columns of the orthogonal matrix.

Growing community of inventors

Trondheim, Norway

Emmanuel Causse