Adam_edit.qxp 24/10/08 11:10 Page 94
4D Physical Simulation of Basin-scale Salt Tectonic Processes and Coupled
Geosciences
Depositional Systems from the Rift Basin to Modern Continental Margin
a report by
Jürgen Adam and Salt Dynamics Group
Department of Earth Sciences, Royal Holloway University of London, and Department of Earth Sciences, Dalhousie University
With the increasing pressure to secure oil and gas resources for the enables the correlation, structural restoration and mechanical
coming decades, petroleum exploration is pushing forwards into analysis of complex salt and fault systems. The derived salt tectonic
underexplored frontier salt basins and their deepwater environments models support the verification of seismic interpretations and
along the Atlantic and Arctic continental margins. Successful petroleum exploration concepts, and reduce risk in exploration activities in
exploration in these geologically, technically and economically deepwater and frontier basins.
challenging areas requires a comprehensive understanding of the basin
history, including a basin-scale tectono-stratigraphic framework. Passive Margin Salt Basin Evolution
However, only a few wells with restricted stratigraphic information are On passive continental margins with syn-rift and post-rift salt
available in frontier areas, in comparison with the well-explored salt sediments, the evolution of a prograding sedimentary wedge is
basins of the Atlantic margins or the deepwater slopes of the Gulf of characterised by thin-skinned extension of the brittle overburden on
Mexico and Brazilian margins. the viscous substratum; examples include the Angolan margin,
2
the
Gulf of Mexico,
3
the Scotian margin
4
and the Brazil margin.
5
For example, in the frontier salt basin beneath the continental slope
offshore Atlantic Canada, only 14 exploration wells have been drilled Differential sedimentary loading causes seaward flow of the viscous
so far in deepwater (>200m) in an area of ~100,000 km
2
.
1
Here, salt sediments and gravity spreading of the brittle sedimentary
disappointing results from the most recent exploration cycle overburden passively moving on top of the weak salt detachment
demonstrate that successful exploration concepts developed in other (see Figure 1A). From the rift stage to the modern passive margin,
salt basins, such as the Gulf of Mexico or the South Atlantic, cannot three evolutionary stages with a characteristic kinematic
be reliably adapted to frontier basins because of their unique segmentation of deformation throughout the basin can be
characteristics, including rift basin geometry, palaeogeography, salt distinguished (see Figures 1B to 1D). Whereas the kinematic
thickness and sediment supply. Even with improved geophysical segmentation is characteristic for all passive margin basins, the
imaging of salt structures on a prospect scale, it is becoming clear duration of the evolutionary stages and the structures developing in
that the evolution of these salt features and their interaction with the kinematic domains are controlled by such factors as:
sedimentation can be analysed successfully only in basin models that
stretch from the initial salt mobilisation in the rift basins to the • basement morphology and geometry of the salt basin;
formation of allochthonous salt nappes and canopies in the modern • salt thickness; and
deepwater slope and basin. • sedimentation pattern and rates.
The Salt Dynamics Group has recently developed a new generation of The early stage (late syn-rift to early post-rift) is characterised by
analogue experiments with 3D strain monitoring to support exploration mobilisation of primary salt with evacuation and overburden
in frontier salt basins. The scaled physical experiments successfully extension in the landward salt basin and salt inflation and
simulate the first-order structures and depositional systems of the overburden contraction in the seaward salt basin (see Figure 1B).
passive margin salt basins, from early post-rift salt mobilisation to Typical structures in the shelf extensional domain are grabens,
the late post-rift allochthonous salt canopy/nappe system. growth faults or passive diapirs. In the seaward contractional domain,
salt inflation, short wavelength folding and local thrusting can occur.
The integration of analogue experiments with high-resolution 3D
strain monitoring, tectonic modelling and seismic interpretation The intermediate stage (post-rift to drift) starts when most of
the original salt has been evacuated from the landward salt
basin. As no new accommodation space is generated, this causes
Jürgen Adam is a Senior Lecturer at Royal Holloway University in London and an Adjunct
Professor at Dalhousie University in Halifax, Nova Scotia. He is a member of the Fault
seaward progradation of sediments on top of the inflated salt in the
Dynamics Research Group and leader of the Salt Dynamics Groups in the Departments of
seaward salt basin (see Figure 1C). Ongoing contraction in the distal
Earth Sciences at Royal Holloway and Dalhousie Universities. Dr Adam is a structural
salt basin is accommodated by long wavelength folding
geologist, geomechanics specialist and physical modeller with more than 15 years of
professional experience. He is developing innovative physical experiment methods to
and salt extrusion, forming extensive canopy systems along the
simulate tectonic processes from structural to margin scale. His research areas include
seaward salt basin margin.
active and passive continental margins, fold-and-thrust belts and their related sedimentary
basins. In collaboration with partners at the Dalhousie University, Memorial University, the
Geological Survey of Canada and industry partners, Dr Adam is investigating salt tectonics The late stage (main drift) begins when most of the salt has been
in generic deepwater passive margin settings and the sedimentary basins of Eastern
evacuated from the salt basin. At this stage, the remaining salt is
Canada. The multidisciplinary studies focus on tectonic–sedimentary processes at passive
continental margins and their relevant industry applications.
trapped in diapir structures or is expelled into the seaward
allochthonous salt system (see Figure 1D). Former structures in the shelf
94
© TOUCH BRIEFINGS 2008
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