Workflows for Geomechanical Restoration and Forward Modelling in Fold and Thrust Belts:Comparison with Geometric Methodologies, Applications and Limitations

Griffiths, Paul¹, Laurent Maerten² (1) BG Group, Reading, Berkshire, United Kingdom (2) IGEOSS, Montpellier Cedex2, France

Fold and thrust belts represent an important environment for world hydrocarbon exploration and production. However, in these settings seismic imaging of subsurface features is often poor due to structural complexity, with limited structural orientation data at depth to constrain interpretations. The geoscientist is required to develop a subsurface model that honours the available data but is often geologically model-driven. Section construction and geometric restoration have a long history of application in thrust belts, providing a consistent set of geometric constraints which help to test the interpretation and geological model. However, geometric techniques are often time-consuming and do not attempt to incorporate any physical deformation of the rocks.

We present an alternative methodology for restoration in fold and thrust belts using geomechanical elastic finite element code that allows simultaneous restoration of all fault blocks to a convergent solution that is repeatable. Using the geomechanical approach, potential interpretation inconsistencies appear as anomalous stress or strain concentrations and gaps and overlaps between the hangingwall and footwall. Modifications to the present-day interpretation can be rapidly and consistently restored to a unique geometry.

We compare the process and results of restorations and forward models using geometric techniques (flexural slip and fault parallel slip) and the geomechanical approach using synthetic and natural examples. The comparison is used to examine the uses and limitations of both geometric and geomechanical restoration approaches.