Use of Prior Information in Gradient-Based History Matching

Abstract

Summary This paper demonstrates how certain geological constraints can be imposed during gradient-based history matching by use of a prior term in the objective function. We extend an existing method of parameter selection (gradzone analysis) to the case in which the prior covariance matrix is nondiagonal. We show that the parameter selection can be made independently of the weight assigned to the prior information, and illustrate how the shape of the gradzones is modified to reflect the correlation structure of the porosity or permeability fields. Finally, the use of the prior term to preserve a relationship between porosity and permeability during the historymatching process is demonstrated.