WORRALL, DAN M., Shell EP International Ventures, Houston,Texas USA, BRADFORD E. PRATHER and JOSEPH STRACCIA, Shell International Research and Technical Services, Rijswijk,The Netherlands

Abstract: Frontier Deepwater Basins: What's Next?

A major portion of volumes discovered to date in the global deepwater play are found in two settings.The first includes basins with Tertiary deepwater clastics deposited upon a mobile substrate of salt or shale, downdip of major Tertiary delta systems. Examples include the northern Gulf of Mexico basin, continental slope of the Lower Congo delta, and Niger delta slope. A second setting includes predominantly stratigraphic traps in Tertiary to Upper Cretaceous submarine fans in a toe-of-slope setting. Examples include major accumulations in Campos basin, Brazil, and the West of Shetlands.

Exploration efforts in frontier basins over the past decade have largely focused on the first of these settings. Mobile substrate provides high trap density and a variety of plays, amplitude technology is useful in lowering trap risk, and the setting is familiar to companies involved in the Gulf of Mexico. Many frontier areas currently being tested fall into this setting, such as the Trinidad slope, the Mahakkam and Tarakan basins of Indonesia, salt basins in northwest Africa, and the Kwanza basin of Angola. Although there are other frontier "mobile substrate" basins still remaining to be tested, numbers are limited.

The second setting is less explored in the global frontier arena. Stratigraphic traps in unconfined, toe-of-slope fans provide large and attractive targets, but with low trap density and less play diversity per exploration block. Low structural relief combined with large trap dimensions make best utilization of amplitude anomalies more difficult. Potential targets however are numerous, and exploration efforts are increasing.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England