Evolution of DHI Techniques in Offshore Nile Delta
By
Hammouda Nada1, Tom R. Williams2
(1) BP Egypt, Cairo, Egypt (2) BP-Egypt, Cairo, Egypt
The first wells in the offshore Nile Delta, positioned solely on structural
seismic
interpretation
, were drilled based on oil agreements resulting in the
abandonment of early gas discoveries. The advent of the Gas Clause Article in
the mid 80’s, where EGPC improved gas terms making it more lucrative to explore
for gas, resulted in more than 25 gas discoveries throughout the offshore Nile
Delta.
More than 100,000 kms of 2D and 30,000 km2 of 3D seismic
data
has been
acquired in the Nile Delta. Advances in
seismic
acquisition and processing
techniques during this period have resulted in improved
data
quality with
successful application of DHI techniques. These included early “bright spot” and
“flat spot” observations, AVO analysis and the use of
seismic
polarity to
pinpoint gas filled zones. These were all influential in the drilling of
discoveries such as Denis, Seth, Hap’y and Baltim.
Seismic
inversion and flat spot enhancement techniques have proven useful in
evaluating the more complex submarine canyon and channel/levee facies that the
latest phase of Pliocene drilling has encountered in Fayoum, Libra, Aztec, Ruby
and Abu Sir.
Seismic
inversion has been used to estimate net pay thickness and
to generate hydrocarbon pore volume maps.
Current challenges for DHI techniques center around more accurate prediction and calibration of how thin “single cycle” gas charged sheet sands might be, distinguishing between residual and producible gas, and understanding differences between conventional gas pay in clean sands and “unconventional” silty, thin bed or low resistivity pay.