Steven G. Henry¹, Al Danforth²
(1) Geolearn LLC, Houston, TX
(2) Consulting Exploration Geologist, Houston, TX

Abstract: New Play Types for the Angolan Deep and Ultra-Deepwater

Beginning with Girassol (1996) and continuing through Orquidea and Xikomba (1999), the offshore of Angola has been providing the industry with giant deepwater discoveries. Abundant source rocks of various ages and presently at various depths (maturity), with overlying sequences of salt structured Tertiary sands and shales have provided the basic components for this deepwater play. If exploration is to continue moving to even deeper waters, new petroleum systems must be identified and new plays developed.

This paper presents new play types, illustrated with seismic examples, for the exploration of Angolan deep (1500-3000 m) and ultra-deep (3000-4000 m) waters. Seismic data, 2-D and 3-D, from Western Geophysical’s African Speculative Surveys, now provide coverage from the deepwater discoveries, over the Crustal Transition Zone and out onto the Mafic / Volcanic Crust. Application of seismic stratigraphic principles have led to the identification a new ultra-deepwater petroleum system and numerous new plays.

This new petroleum system developed overlying Late Cretaceous basins, containing up to 2000 m of sediment, which are observed onlapping the surrounding mafic / volcanic highlands. Deposition (2000-3000 m) of abyssal Tertiary sediments, resulted in the Cretaceous sediments entering into the oil/gas window, suggested by apparent Hydrocarbon Indicators. Plays within the ultra-deep include draped basin floor fans and stratigraphic traps. Plays overlying the Crustal Transition Zone include structures related to recent (Pleistocene?) compression, drape/onlap of the transitional horst, and salt related structures on the western limit of the salt basin.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana