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.