Structural Interpretation Using a Three Dimensional Mass-Spring Restoration

Shackleton, J. Ryan¹, Graham Seed¹, William Sassi¹, Serena Jones¹, John Grocott¹ (1) Midland Valley Exploration Ltd, Glasgow, United Kingdom

Three dimensional structural restoration of folded and faulted strata has traditionally been accomplished using a variety of geometric and mechanical techniques, often in combination. Geometric techniques are computationally inexpensive, but lack the full stress solution and may be limited to plane strain. In contrast, mechanical techniques produce stress solutions implicitly, but are computationally expensive and may not efficiently model dynamic processes or large strains. We present a new mass-spring technique for structural restoration that is computationally inexpensive, accounts for heterogeneous displacement, models dynamic processes, and is based on physical laws of displacement. Geologic surfaces and volumes are represented by elements with finite mass connected by springs, and the point dynamics equations for each mass are integrated over the surface or volume for a given time step. Dynamic processes and large deformations are implicit in the model formulation and the stress/strain for any mass can be computed based on motions of adjacent masses. We present two case studies: 1) an inverted rift sequence consisting of a non-cylindrical, fault-cored anticline and 2) a complexly faulted extensional basin. Restoration of the non-cylindrical fault cored anticline demonstrates the advantages of time step based dynamic modelling using a non-plane strain restoration. Restoration of complex block faulting in extensional regimes demonstrates the advantages of a dynamic restoration that closes fault gaps while minimizing strain.