First Steps in Deep Offshore Exploration: The Angola Case History

Marc René Blaizot
TOTAL E§P, Paris, France

At the beginning of the 90's, the successful exploration of the Angolan Shelf orientated towards Cretaceous targets was reaching its peak. The oil industry, driven both by the lack of remaining potential and by the determination of SONANGOL to prove new national resources, was consequently looking closely at the neighbouring deep water areas.
TOTAL started a regional geological study aimed at determining whether significant plays and traps could exist in these totally undrilled areas.
This study was mainly based on the interpretation of newly acquired 2D seismic and their long distance well calibration together with the examination of possible analogs. The resulting regional synthesis highlighted:
The tectonics and depositional history
The distribution and maturity of source-rocks
The age and mapping of possible seal-reservoir pairs
The nature and inventory of the different traps.
Finally, a very prospective exploration domain with development of huge structures, good maturation context and possible turbiditic plays in the Tertiary series emerged.
Consequently, TOTAL ranked the different exploration blocks defined by SONANGOL as follows: block 17, 14, 16 and 15 and subsequently became operator of block 17 in 1993. The two main criteria for selection were: oil versus gas risk and the existence of prominent raft-type structures. This geological study opened a new, world-class, petroleum province due to the size and productivity of the first discovery, Girassol, in 1996.
This demonstrates that in frontier exploration, regional geological understanding is the essential step in selecting a promising portfolio, avoiding killing parameters and therefore focusing upon first-class exploration prospects and subsequent commercial successes.
This has allowed Angola to enter the first league of the one million barrel a day deepwater producers.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece