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Abstract: An Example of Hybrid Petroleum System in Offshore Angola

B. C. Duval, G. Choppin De Janvry, J. C. Heidmann, J. L. Pittion, H. L. Ten Haven

Block 2 is located on the western Lower Congo basin, in offshore Angola.

In the Pinda Albian carbonate reservoirs, oil was often found together with gas and gas content generally increases westwards.

The Pinda structures are related to the Aptian halokinesis resulting in the segmentation of the Pinda carbonate platform into allochthonous blocs (rafts).

Three main source-rocks were identified.

Strong source potential was locally observed in the lacustrine Pre-salt Bucomazi equivalent. The major part of this section is presently in the gas window.

The principal marine source-rock is restricted to the upper part of the Iabe formation (mainly Senonian and Paleocene). The Iabe is in the oil kitchen over most of the western part of the block.

The Tertiary Malembo marine section has a gas and condensate potential in the westernmost area of the block (Miocene trough).

Oil tested in the Pinda formation belongs to two groups. Oils from the easternmost part of the block are of pure lacustrine origin and were generated in the Pre-salt. All the other oils have a mixed origin (Iabe and Pre-salt).

Basin modelling was performed to assess the timing of generation and migration and the migration paths. The development of overpressure at the boundary between the Malembo and the Iabe controls the hydrocarbon migration.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France