Insights into Fault Related Folding Provided by 3D Structural Restorations Using Mechanical Constraints
Abstract
Most current methods of restoring three-dimensional structural models are based on two-dimensional (horizon or cross-section based) approaches that impose restoration kinematics and do not consider mechanical rock properties. In contrast, we apply a new volumetric (3D) restoration method based on mechanical finite element techniques that has value in characterizing complex geologic structures and hydrocarbon traps. To perform these restorations, we define structures using 3D seismic reflection data. Stratigraphic horizons, faults, and detachments are mapped and represented as triangulated surfaces, which are then employed to constrain volumetric (tetrahedral) meshes. Mechanical properties (bulk and shear moduli), which can vary between stratigraphic intervals, are assigned to the mesh and used to balance competing volume conservation and strain terms in a strain energy minimization process. This allows certain rock units to behave competently during restoration, while other weaker units localize strain. Restorations are performed by flattening datum horizons, and simultaneously recovering both folding and faulting deformations. Three-dimensional displacement and strain fields are calculated using finite element techniques implemented in Gocad's Structural Restoration Plugin (Muron, 2005). We employ this restoration approach to gain insights into fault-related folding mechanisms, including the influence of major strength contrasts, fault geometries, and flexural slip surfaces on fold kinematics. Through a series of case studies from the deepwater Niger Delta, the Caspian Sea, southern California, and China, restorations are evaluated based on their inferred displacement and strain fields, and compared with patterns of syntectonic growth strata to assess the viability of restoration kinematics. Our results provide insights into the folding mechanisms of several classes of fault-related folds, and help to define histories of structural growth. Moreover, the strain fields derived from the restorations might also prove of use in constraining patterns of reservoir-scale deformation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.T52A..02S
- Keywords:
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- 8005 Folds and folding;
- 8010 Fractures and faults;
- 8020 Mechanics;
- theory;
- and modeling