3-D Restoration Using Elasticity and/or Elastic Relaxation

Moretti, Isabelle C.¹, Marc O. Titeux² (1) IFP, Rueil Malmaison, France (2) ASGA-CRPG, Vandeaouvre-les-nancy, France

Tools for 3D restoration are now available. A complex meshing of the model takes into account heterogeneities due to the layering and facies variation. By coupling geometric modeling software and a mechanical finite-element code, the geologist is now able to impose the displacement on the main faults, in order to get an adequate restored geometry. Unfolding with a mechanical approach also allows computing 3D strain and stress fields within the main blocks. The geometry at various time steps, as well as the major fault offsets, is defined by the user using a geomodeler, whereas the restoration within the main “blocks” will be computed by a finite-element mechanical code. For the unfolding, one needs to define the deformation mode: elasticity, under the hypothesis of large deformation, seems reasonable as a first approximation. It allows easy reverse modeling. Facing the same problems, approaches based on a dynamic-relaxation solution are also possible. Resolution using dynamic relaxation is based on the determination of the stationary solution of the transient problem. It aims at accommodating the displacement and velocity fields along the main faults by computing iteratively the solution to the problem with new interface forces or degenerated cinematic constraints.

We will show 3D restoration in complex areas using both methodologies and compare the results in terms of computed initial geometry, dilatation, stress and strain tensors. The differences will be highlighted on the computed zones of high internal deformation that we use to interpret as zone of higher fracturation.