Understanding Paleo-Stress and Paleo-Strain History of the Lusitanian Basin Using Restoration and Forward Modelling

Abstract

Paleo-stress and paleo-strain models allows for better understanding of basin geological history. This, in turn, leads to more accurate prediction of hydrocarbon migration paths, and provide an insight on the trap formation mechanisms. To build a model describing geological history, an approach combining forward modelling and restoration might be applied (Anis, L. et al.).

The geometric restoration scheme (Petersen & Hjelle, 2008) is used for quantifying deformations related to folding and faulting processes. Applying fundamentals of classical differential geometry, a metric tensor that quantifies spatial distribution of deformation is derived. Restored geometrical state together with the strain tensor, mechanical properties and rheological models allows for computing of the correspondent stresses. Stress concentration areas indicate places where the faults or plastic deformations are formed. In particular, fractured areas not visible from the seismic data, might be identified in such a way.

However, presence of salt-related deformations considerably complicates this task since restoration of deformation in such areas is much more challenging than in the conventional basins. This is mainly due to the ability of salt to flow, dissolve and to hide deformation, and that salt movement is inherently three-dimensional. The principles of regional balance of extension and contraction, plainstrain deformation, and conservation of area and volume, commonly used in restoration, must be used with care (or not used at all) in salt-related restoration, especially if diapirs are present (Rowan & Ratliff, 2012). Therefore, additional forward modelling tools should be adopted.

Approach described above is used for building paleo-stress and paleo-strain model of the Lusitanian basin.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015