4D Modeling of the Interaction between Salt Tectonic Processes and Dynamic Deposition Systems at Passive Margins from the Shelf to the Deepwater Slope

Juergen Adam, Csaba Krezsek, and Djordje Grujic
Salt Dynamics Group, Dalhousie University, Halifax, Canada

Sedimentary basins along the Atlantic passive margins exhibit extensive thin-skinned extension over salt sediments. The gravity-driven tectono-stratigraphic evolution of the depocenters in the shelf, slope and deepwater areas cause complex feedbacks between sedimentation, faulting and salt mobilisation from basin to reservoir scales. Basin and petroleum system modelling of these dynamic depositional environments, especially in the deepwater with limited well control remains challenging.
The Salt Dynamics Group utilises 4D scaled physical experiments to simulate the structural evolution of passive margins during progradation of depositional systems on salt substratum from the late syn-rift to post-rift stage. Fault kinematics, surface deformation and subsidence are monitored by high-resolution 2D/3D optical image correlation (PIV - Particle Imaging Velocimetry). The displacement and strain data obtained by PIV analysis are compatible with input data or results from numerical deformation (FE/DE) and basin modelling techniques. 3D models and structurally balanced cross sections are built from experiment sections and time-series 3D surface and strain data to provide insights in the basin history and mechanics of fault and salt-structures. This integrated modelling approach allows us to quantitatively assess: 1) the timing and mechanisms of faulting and salt mobilisation, 2) the role of variable sedimentation patterns and rates, and 3) the kinematic coupling between extension in the shelf and slope and compression in the deepwater basin.
The experiments reproduce the complex 3D structures of passive margins detached on salt, including crestal grabens, landward and seaward growth fault/roller structures, diapirs, turtle structures, canopies, and allochthonous salt sheets. Distinct kinematic sub-domains in the shelf and deepwater basin are characterised by characteristic deformation styles controlled by the salt thickness, pre-salt basement topography, and sedimentation rates and patterns. Individual grabens in the shelf show highly variable and localized subsidence patterns and are kinematically linked with early deep-water compressional belts and late allochthonous salt canopies. Our results show that a strong relation exists between sedimentation, rate of extension and dominant structural styles. Starved sedimentation enhances passive diapirism and canopy formation. Low sedimentation rates favor passive diapirs, expulsion rollovers, and basinward growth fault/rollover systems. Conversely, high sedimentation rates support rapid development of early basinward and late landward growth fault/rollover systems or can seal earlier extension structures. Thus, structural patterns of fault and salt structures have the potential to give insights into the dynamics of depositional systems.
We are confident that in the near future mechanical fault concepts and improved interpretation templates for salt-related structures and depositional systems derived from innovative 4D physical simulation can significantly improve basin modelling and petroleum system modelling of structurally complex basins and complex reservoirs.

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands