DYNAMICS and ACTIVE PROCESSES - International Lithosphere ...

ILP TASK FORCE on SEDIMENTARY BASINS
2010 International Workshop
November 7-12, 2010, Tirana (Albania)
IMPACT of BASEMENT CONFIGURATION and SEDIMENT ARCHITECTURE on
GRAVITY GLIDING on UNDER-COMPACTED SHALE DECOLLEMENTS
Nadine ELLOUZ-ZIMMERMANN*, Raymi CASTILLA*, François ROURE*, Khalid
AL HOSANI**, Saleh AL MAHMOUDI** and Abdullah GAHNOOG **
*IFP Energies Nouvelles, 1-4 av de Bois-Préau, 92856 Rueil-Malmaison, France.
** Ministry of Energy, Abu Dhabi, Emirates
What are the dominant parameters which governed the tectonic style in gravity-driven
complex tectonics on deep shale décollements levels along margins? One of the first order
parameter concerns overloading process on platforms. Associated, either to intense
erosion/deposition in compressive margins, or driven by rivers which convey huge amount of
sediment up to deltas, the overloading in strongly link with the development of overpressure
cells within deep shale layer. Location of the depocenters or of the prograding deltas through
time, should also be a critical parameter for the evaluation of deformed traps.
To be able to identify some criteria of the generation of deformed zones, the architecture of
the deep structures was analyzed through time, via analogue models, in order to evaluate the
impact of several parameters which could vary in 3D. All the models have been acquired with
X-Ray tomography at IFP, and calibrated at a first order scale on subsurface data from
Chamak Survey- in the Makran compressive margin, in the Sinu accretionary prism and in the
East Oman Margin, atypical passive margin developed on the Oman Emirates Fold-and
Thrust belt.
Several sensitivity tests have been done on décollement level configuration; dip, interruption
on basement blocks, and various ratio between ductile and brittle layers..
It appears that the characteristics of initial configurations either of the basement, or of the
sedimentary patterns governed not only the distribution and the direction of the normal
growth faults system, but also the location and the amplitude of the down-slope compressive
deformation.
Cylindrical progradations of various extension -above or behind the compressive front, can
freeze the gravity-driven compressive front and evenly can be dissected by a new growth fault
system, or reactivated and translated downslope.
Out coming results allow 1) to improve seismic interpretation in blind areas when
overpressured shale mobilization processes dominated 2) to estimate the timing and the
nature of the deep structures development, and 3) to be predictive on the preservation of the
deepest traps.
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