10 | Halliburton Landmark
were similar to those of the present day, which
preferentially follow long-lived structural trends.
The largest modern-day catchment areas can,
therefore, be used to help predict the likely
distribution of the thickest syn-rift siliciclastic
reservoirs offshore, which are interpreted to be
proximal to shorelines, trapped within rifted lows
(Figure 4).
Our sediment budget calculations and source-
to-sink analysis show that, during the Miocene,
the bulk of sediment sourced from the adjacent
Red Sea rift shoulders was directed westward
into the Nile catchment, transported north
into the Eastern Mediterranean (Macgregor,
2012). Sediment balancing based on present-
day catchment areas along the Egyptian Red
Sea margin suggests siliciclastic input into the
Northern Red Sea Basin was predominantly
locally derived, fed by small catchment areas
(Figure 4), which could result in relatively thin,
poorly-sorted sandstones with inferior reservoir
quality.
Additional sources of sediment for the early-
rift succession could have been supplied by
uplifted fault blocks along intra-basinal faults. In
the Northern Red Sea Basin, early rift-related
exhumation and reworking of older Nubian
facies along the crests of these tilted fault blocks
may have provided a source of reservoir quality
sandstones into the adjacent rifted lows.
Syn-rift Carbonate Reservoir
While siliciclastic deposition was focused into
structurally controlled hanging walls, Early to
Middle Miocene deposition of shallow-marine,
peritidal to subtidal carbonates developed on
isolated, uplifted fault-blocks (Koeshidayatullah,
2016) (Figure 2). Early Miocene carbonates signify
primary reservoirs in several Gulf of Suez fields
and could, therefore, represent a promising target
in the Egyptian Red Sea.
Outcrop analogues from the Saudi Arabian
Midyan Basin suggest that large benthic
foraminifera and reef builders, such as coralline
red algae and sclerectinian corals, were the main
carbonate producers, formed preferentially during
periods of relative sea level rise over footwall
highs. The reservoir quality of these carbonates
could also have been enhanced by periodic
Exploration Insights | 11
subaerial exposure and karstification during
tectonic uplift and/or eustatic sea level fall, based
on the presence of vuggy porosity in platform-
top successions of Midyan Basin outcrops
(Koeshidayatullah, 2016).
A NOTE ON SEALS AND TRAPS
Within the sub-Messinian salt stratigraphy
of the Gulf of Suez, intra-formational, basinal
mudstones immediately overlie proven Early
Miocene siliciclastic reservoirs. Seals of a similar
nature are expected across the Northern Red
Sea Basin, indicating seal presence for lower
syn-rift reservoirs to be of relatively low potential
risk. In addition, a thick Late Miocene evaporite
sequence provides an effective seal for Middle to
Late Miocene sub- and intra-salt siliciclastic and
carbonate reservoirs across most of the basin.
Hanging walls of basin-bounding faults are likely
structural traps for both pre-rift Nubian and
syn-rift siliciclastic reservoirs, analogous to the
Kingfisher Field of Uganda and the Ngamia Field
of Kenya. This play is underexplored. However,
reservoir size is expected to be limited here
by hyperextension, the dense faulting in the
area, and diminished sand supply from the rift
shoulders due to relatively small catchment
areas. Directly beneath the salt, Middle Miocene
carbonate buildups could represent promising
targets, likely to be developed over the largest
outboard paleo highs. Additional traps are
expected to be provided by salt mobilization,
together with stratigraphic pinch-out, in the intra-
and post-evaporite sequence.
CONCLUSIONS
There is considerable petroleum potential in the
Egyptian Red Sea, and a high chance of future
exploration success. The Gulf of Suez is a suitable
analogue; however, this work highlights the
fundamental differences in the structural and
thermal histories of the two areas, meaning that
any comparisons have to be undertaken with
caution.
High and variable heat flow, variable burial depths,
and thick, mobile salt deposits in the Egyptian Red
Sea likely contribute to significant spatial variation
in source rock maturity, and in the potential
loss of porosity with depth, therefore, creating
uncertainty in charge and reservoir quality. McKenzie, D. 1978. Some remarks on the development of
sedimentary basins. Earth and Planetary Science Letters, v.
40, no. 1, p. 25-32. (XURBB_394592).
Petroleum system modeling in Permedia has
shown that gas is likely to be the dominant phase,
except in areas close to the shore where heat flow
is reduced, and over shallow basement blocks. Pigott, J.D., G. Teferra and Y.E. Abdelhady 1996. Late Cenozoic
Paleo-Heatflow of the red Sea: regional Implications for
tectonics and Hydrocarbon Exploration. Proceedings of the
EGPC 13th Petroleum Exploration and Production Conference,
Cairo. Egyptian General Petroleum Corporation (EGPC), p. 313-
339. (XURBB_640721).
Syn-rift clastic plays are expected to be limited
within the offshore, largely due to diminished
sand supply from the rift shoulders and relatively
small catchment areas, but carbonate plays may
be of greater relative importance, particularly
above outboard rifted highs. The exploration of
pre-salt plays is likely to be complicated by the
uncertain preservation of the pre-rift stratigraphy
within the basin, which would require improved
seismic to be resolved, but there is strong
evidence of at least locally preserved Nubian,
particularly within hanging walls.
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ACKNOWLEDGMENTS
The authors would like to acknowledge the contributions
of Duncan Macgregor, who provided valuable guidance on
the geological theory and technical content of this article,
and Sigrún Stanton would like to acknowledge her co-author
Natasha Dowey.
AUTHOR
Sigrún Stanton — Senior Geoscientist, Regional
Petroleum Geoscience, Halliburton Landmark
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