A methodology for efficiently populating faulted corner point grids with strain

Abstract

This article describes an algorithm to compute finite strain in faulted corner point grids using the software Havana. The algorithm is based on a simple fault displacement formula, and a volumetric computation of strain in the grid's deformed configuration. The volumetric computation of strain is tested by comparing the finite strain of a 3D trishear model calculated by this method, with that calculated by the tetrahedrons method. The agreement between both methods confirms the validity of the volumetric strain computation. The algorithm is applied to synthetic models of one and three intersecting normal faults, and to a real model with seven faults, the Emerald Field. In all cases the computed finite strain is consistent with the fault network and with the variation of slip along the faults. There is one parameter that affects the computation significantly: the drag radius ( r d ) or extent of folding across a fault. Low r d models yield high finite strain and strain gradients but limited fault interaction, and vice versa. Using empirical relations between fault throw and damage zone width, r d can be narrowed down and further constrained by evaluating the quality of the grid's restoration. The strain algorithm can be integrated easily into a reservoir modelling workflow and in stochastic modelling. The algorithm provides criteria for conditioning the distribution of deformational features within the reservoir zones affected by faulting, based on the magnitude of finite strain.