Method of modelling a subterranean region of the earth

Abstract

A method of modelling a subterranean region of the Earth at a first location comprises the steps of: providing geological data; selecting a plurality of facies; providing a distribution of rock physics probability with spatial dependencies; approximating the rock physics probability at the first location with at least one distribution per facies utilizing the spatial dependencies in the rock physics probability distribution; and performing a Bayesian inversion at the first location using the approximation of the rock physics probability distribution. The method may also employ a window comprising the first location and at least one further location.

What is claimed is: 
     
         1 . A method of determining a rock facies in a subterranean region of the Earth at a first location, comprising the steps of:
 obtaining seismic data associated with said region;   selecting a plurality of facies;   providing a first rock physics probability distribution with spatial dependencies;   providing a second rock physics probability distribution around the first location comprising at least one probability distribution per facies, wherein the spatial dependencies in the first rock physics probability distribution are utilized, such that the second rock physics distribution provides a simplifying approximation of the first rock physics distribution; and   performing a Bayesian inversion at the first location by a computer processor using the second rock physics probability distribution to predict the probability of the rock facies at said location taking into account said seismic data, in order to indicate a presence of said facies in said region.   
     
     
         2 . The method as claimed in  claim 1 , wherein the Bayesian inversion step provides a posterior rock physics probability distribution of the rock physics probability distribution. 
     
     
         3 . The method as claimed in  claim 2 , wherein the step of approximating the posterior rock physics probability distribution comprises summing the approximating distributions in the window. 
     
     
         4 . The method as claimed in  claim 1 , wherein the at least one distribution is Skew Normal. 
     
     
         5 . The method as claimed in  claim 1 , wherein the at least one distribution is Elliptical. 
     
     
         6 . The method as claimed in  claim 1 , wherein the at least one distribution is Gaussian. 
     
     
         7 . A computer program product embodied on a non-transitory computer readable medium, the computer program product comprising computer-executable instructions to perform the method as claimed in  claim 1 . 
     
     
         8 . A computer programmed to perform the method as claimed in  claim 1 . 
     
     
         9 . A method of determining a rock facies in a subterranean region of the Earth at a first location comprising the steps of:
 obtaining seismic data associated with said region;   selecting a plurality of facies;   providing a first rock physics probability distribution with spatial dependencies;   providing a second rock physics probability distribution around the first location comprising at least one distribution per combination of facies in a window comprising the first location and at least one further location, whereby the second rock physics distribution provides a simplifying approximation of the first rock physics distribution; and   performing a Bayesian inversion by a computer processor using the second rock physics probability distribution to predict the probability of the rock facies at said first location taking into account the seismic data, in order to indicate a presence of said facies in said region.   
     
     
         10 . The method as claimed in  claim 9 , wherein the Bayesian inversion step predicts the probability of the facies or the facies combinations in the window. 
     
     
         11 . The method as claimed in  claim 9 , wherein a likelihood term in the Bayesian inversion is evaluated directly from at least one rock physics distribution per combination of facies. 
     
     
         12 . The method as claimed in  claim 9 , wherein the combinations of facies exclude impossible combinations of facies. 
     
     
         13 . The method as claimed in  claim 9 , wherein the combinations of facies exclude physically impossible combinations of facies. 
     
     
         14 . The method as claimed in  claim 13 , where combinations of facies are excluded based on prior information. 
     
     
         15 . The method as claimed in  claim 9 , wherein the combinations of facies exclude combinations of facies that would not be expected to occur naturally. 
     
     
         16 . The method as claimed in  claim 9 , wherein the combinations of facies exclude combinations of facies that would not be expected to occur naturally. 
     
     
         17 . The method as claimed in  claim 9 , wherein the approximation of the rock physics probability is the same for all locations that have the same facies configuration in the window. 
     
     
         18 . A computer program product embodied on a non-transitory computer readable medium, the computer program product comprising computer-executable instructions to perform the method as claimed in  claim 9 . 
     
     
         19 . A computer programmed to perform the method as claimed in  claim 9 . 
     
     
         20 . A method of determining a rock facies in a subterranean region of the Earth at a first location, comprising the steps of:
 obtaining seismic data associated with said region;   selecting a plurality of facies;   providing a first rock physics probability distribution with spatial dependencies;   obtaining a second rock physics probability distribution comprising at least one probability distribution per facies utilizing the spatial dependencies in the first rock physics probability distribution wherein the second rock physics distribution provides a simplifying approximation of the first rock physics distribution around the first location; and   performing a Bayesian inversion at the first location by a computer processor using the second rock physics probability distribution to predict the probability of the rock facies at said location taking into account said seismic data, in order to indicate a presence of said facies in said region.   
     
     
         21 . A method of determining a rock facies in a subterranean region of the Earth at a first location comprising the steps of:
 obtaining seismic data associated with said region;   selecting a plurality of facies;   providing a first rock physics probability distribution with spatial dependencies;   obtaining a second rock physics probability distribution comprising at least one distribution per combination of facies in a window comprising the first location and at least one further location, wherein the second rock physics distribution provides a simplifying approximation of the first rock physics distribution around the first location; and   performing a Bayesian inversion by a computer processor using the second rock physics probability distribution to predict the probability of the rock facies at said first location taking into account the seismic data, in order to indicate a presence of said facies in said region.   
     
     
         22 . A method of determining a rock facies in a subterranean region of the Earth at a first location, comprising the steps of:
 obtaining seismic data associated with said region;   selecting a plurality of facies;   providing a first rock physics probability distribution with spatial dependencies;   approximating the first rock physics probability distribution around the first location with at least one probability distribution per facies utilizing the spatial dependencies in the first rock physics probability distribution, to obtain a simplified, second rock physics distribution; and   performing a Bayesian inversion at the first location by a computer processor using the simplified, second rock physics probability distribution to predict the probability of the rock facies at said location taking into account said seismic data, in order to indicate a presence of said facies in said region.   
     
     
         23 . A method of determining a rock facies in a subterranean region of the Earth at a first location comprising the steps of:
 obtaining seismic data associated with said region;   selecting a plurality of facies;   providing a first rock physics probability distribution with spatial dependencies;   approximating the first rock physics probability distribution around the first location with at least one distribution per combination of facies in a window comprising the first location and at least one further location, to obtain a simplified, second rock physics distribution; and   performing a Bayesian inversion by a computer processor using the simplified, second rock physics probability distribution to predict the probability of the rock facies at said first location taking into account the seismic data, in order to indicate a presence of said facies in said region.