Rift, Compartmentalisation and Evolution of Tilted Fault Blocks as Expressed by the Lower Miocene Abu Zenima and Nukhul Formations Suez Egypt
By
Chris Jackson1, Rob Gawthorpe1, Mike Young1, Jim Stewart2, Dave Pivnik2, Ian Sharp1
(1) University of Manchester, Manchester, United Kingdom (2) BP (Gulf of Suez Exploration Company), Cairo, Egypt
Although tilted fault blocks are common traps within rift basins more subtle
and complex structural and stratigraphic traps can be developed during fault
zone evolution by the growth, interaction and linkage of fault segments. The
early syn-rift Abu Zenima and Nukhul Formations (Lower Miocene) of the Suez Rift
can be used to determine the early rift structure. Outcrop studies in the Hammam
Faraun fault block
indicate that initial fault activity was distributed across
the fault
block
on short (1-4 km long), low displacement (<1 km) segments. These
initial segments either linked to form longer fault zones, or became inactive
during the first 6-8 Myr of rifting. Displacement progressively localised onto
>25 km long border fault zones that bound the present-day major tilted fault
block
, and many of the early intra-
block
fault zones became inactive. In the N.
October and East Tanka areas in the central Gulf of Suez, the Abu Zenima and
Nukhul Formations form hydrocarbon accumulations that are compartmentalized,
commonly lack hydrodynamic continuity, and which have different oil/water
contacts and hydrocarbon types. Reservoir distribution and compartmentalization
is interpreted to reflect deposition in early fault-controlled depocentres that
formed prior to the development of the main faults controlling the October and
East Tanka fields. Thus understanding the growth, linkage and death of fault
segments and reconstruction of the early rift structure has important
implications for subtle trap and reservoir distribution in rift basins.