Structural Restoration of Geological Structures With Viscous Stokes Flow - Principle and First Results

Abstract

Summary Restoration of geological structures is commonly used to assess past basin geometry from present-day structures. In geomechanical restoration, numerical methods to date consider the rock properties as fully elastic and the faults as frictionless contact surfaces. However, salt bodies have been proven to behave as Stokes viscous fluids in geomechanics, and faults appear in rocks reaching a plastic limit inside a shear zone. In order to take these behaviours into account, we introduce a new geomechanical restoration scheme based on Stokes equations. Such a strategy seems reasonable for three main reasons. First, rocks have been found to be mainly ductile in large deformations under long time periods (1e5 to 1e9 years). Second, these equations allow the modelling of other rheologies and boundary conditions closer to natural ones. Third, the reversibility of the Stokes equations can be used to compute the reverse motion of a geological domain. Our restoration scheme is implemented in a software called FAIStokes. The classic forward modelling part of this software is validated through relevant benchmarks. First tests, including van Keken (1997) &s benchmark, on the more innovative backward modelling part, show the great potential of the proposed scheme for restoration using only mechanical (i.e. no geometrical) conditions.