3D Chronostratigraphic Coordinate System Based on Geomechanical Restoration

Geological structures are generally deformed, making the present-day Euclidean distance inappropriate for applying geostatistics. Considering this, chronostratigraphic coordinate system maps geological models into a regular chronostratigraphic space, where deformations (especially those due to both faults and folds) have been removed (Mallet, 2004). Three curvilinear coordinates are used for this mapping, among which a time coordinate, inspired from H. E. Wheeler's work (1958), and two paleogeographic coordinates corresponding to the location of each particle at deposition time. To-date, chronostratigraphic coordinate system has been implemented by Moyen and Mallet (2004), Jayr et al. (2008), as a global optimization method which computes the three coordinates from chronostratigraphic interpretations. In this work, we propose instead to use sequential geomechanical restoration to compute paleogeographic coordinates. Geomechanical restoration is a way to infer the original position of a horizon taking rock physics into account. Each layer is restored into depositional state, which provides the paleogeographic coordinates of its hanging wall. Doing so, it is possible to capitalize on restoration efforts to build a chronostratigraphic coordinate system, accounting for rock rheology and for the deformation path inferred from the sedimentary record.