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7th Middle East Geosciences Conference and Exhibition
Manama, Bahrain
March 27-29, 2006
Characterization
of Fault Zones in Early Cretaceous
Carbonates
, Offshore
Abu Dhabi
ZADCO, P.O. Box 46808, Abu Dhabi, United Arab Emirates, [email protected]
Fault zones developed within Early Cretaceous reservoir
facies and intervening dense limestones, due to predominantly
wrench-reactivation activity on deep basement faults, are characterized by high linearity, small vertical offsets and
anastomosing to en-echelon nature in offshore fields. Consideration of the vertical linkage of these faults, from seismic
attribute data, display organized patterns of continuity, relaying to soft linkage and discontinuity, in response to the
individual layering and alternating dense-
reservoir
heterogeneity of the
reservoir
sequence. Similar changes occur through
seal sequences, highlighting distinct stratigraphic controls on fault propagation.
Reservoir
/ dense limestone fault zones
display differences in:
- Fault zone character
- Individual structural elements / internal structure
- Fault rock types
- Fault behaviour
- Reactivation susceptibility
- Cementation & structural accessed diagenetic
reservoir
degenerative effects
- Associated damage zone / fracture areole development
- Complexities inherent from juxtaposition of thin-layered reservoirs.
Such complexities, supported by dynamic characterization
, result in both fracture dominated ‘conductive' fault-fracture
zones and cemented/smeared ‘sealed' damage zones in the reservoirs, but particularly within the more thinly layered ones
(metric to several metres thick sequences). Deformation style and fault continuity becomes less heterogeneous in thicker
reservoirs where the array of effects is less diverse and fault behaviour and fracture zone effects are more limited and
predictable.
Identification of the relevant kinematic affinity, predominantly wrench reactivation, fault linkages and tectonic model
(repeated reactivated ‘shuffling' on deep faults propagating rheologically controlled fault segments into cover sequences)
provide an improved framework for understanding fluid flow. Consequently, it is no surprise that on production thinner pays
behave in contrasting fashion, with proportionately more fracturing and faulting and reservoir
degenerative effects, to thicker
zones on production.