Patent ID: 9488047
Filing Date: 2016-11-08
CPC Classification: E21B

Claim Text:
1. A method for creating an amended realization of a geostatistical model of a subterranean hydrocarbon reservoir, wherein: a) said amended realization is based on a current realization of the model; b) said current realization comprises at least one petrophysical parameter value for each of a plurality of volume cells; and c) a covariance matrix is associated with the model, wherein the covariance matrix contains information about variance and statistical inter-dependence of estimated parameter value or values of the model; wherein the method comprises the steps of: d) creating a plurality of further model realizations from random seeds; e) creating an approximation matrix containing modified parameter values from said plurality of further model realizations, wherein the approximation matrix comprises series of column vectors, each column vector corresponding to one realization, wherein dimension of the approximation matrix is smaller than dimension of a true covariance matrix, wherein an updated parameter value is calculated by subtracting an average value of the parameter from the parameter value; f) deriving from the approximation matrix approximate eigenvectors and approximate eigen values which are approximations of the eigenvectors and eigen values of the covariance matrix by performing singular value decomposition on the approximation matrix; g) using the approximate eigenvectors and approximate eigen values in a Karhunen-Loève expansion to derive one or more amended realizations.