--> ABSTRACT: Crustal Structure, Rift Tectonics and pre-Salt Stratigraphy beneath the Ultra Deep Water Area Offshore Angola: Results from Reprocessed Seismic Data, by Joaquim Boavida, Erling Vågnes, Paulino Jeronimo, Mateus de Brito, Murthy Inkollu, Jose Peliganga, and Murray Symonds; #90906(2001)

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Joaquim Boavida1, Erling Vågnes2, Paulino Jeronimo3, Mateus de Brito4, Murthy Inkollu3, Jose Peliganga5, Murray Symonds4

(1) Universidade Agostinho Neto, Luanda, Angola
(2) Norsk Hydro Angola, Luanda, Angola
(3) Sonangol DPP, Luanda, Angola
(4) SonaWest, Luanda, Angola
(5) Elf Angola, Luanda, Angola

ABSTRACT: Crustal Structure, Rift Tectonics and pre-Salt Stratigraphy beneath the Ultra Deep Water Area Offshore Angola: Results from Reprocessed Seismic Data

Reprocessing of 2D seismic data was undertaken as part of a joint effort between University Agostinho Neto, Sonangol DPP, Western Geophysical and Norsk Hydro Angola, aiming to understand the crustal structure, rift-history, and pre-salt stratigraphy beneath the UDW area offshore Angola. Reprocessing enhanced the imaging of pre-salt stratigraphy and crustal structure and confirmed the existence of strong reflections at 9 s twt, interpreted to originate at the MOHO or in the lowermost crust. Crustal extension is estimated at b=2-2.5. The study area is underlain by three half grabens bounded by down to the west faults. Maximum depth to the base of the syn rift is > 8 km. Maximum thickness of pre-salt strata is > 3.5 km. Graben fill was divided into 4 sequences: 1. Early rift. Sedimentation kept up with accommodation. These strata are difficult to map. 2. Main rift phase. Thin strata deposited mainly as fault aprons. Topographic and/or bathymetric relief was probably large. 3. Basin fill onlapping towards both the fault scarps and hanging wall crests. This sequence may have source rock potential. 4. Regional basin fill burying the crests of the half grabens beneath up to 1.5 km of sediments. Tectonic activity during the two later phases was minor. Based on regional analogues it is probable that the pre-salt strata beneath the UDW area offshore Angola contain petroleum systems similar to those in Cabinda and onshore Kwanza. Acknowledgement: The authors thank Sonangol and Western Geophysical for reprocessing and permission to publish these data.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado