--> Abstract: The Petroleum System of Campos Basin, by R. Jahnert, A. França, L. Trindade, C. Quintaes, P. Santos, J. Pessoa, and R. Bedregal; #90933 (1998).

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Abstract: The Petroleum System of Campos Basin

Jahnert, Ricardo; Almério França; Luiz Trindade; Cláudia Quintaes; Paulo Santos; Jonilton Pessoa; Ricardo Bedregal - Petrobras/E&P/Cenpes

The petroleum system of Campos basin contains ten billion cubic meters of discovered oil in place and 800 billion cubic meters of natural gas, comprising one of the most prolific sedimentary basins in South America. It is located in southeast Brazil covering about 100,000 km2 with 44 oil fields, seven giants, holding up to 85% of total Brazilian oil reserves and 40% of total natural gas reserves.

The Campos basin produces mostly from turbiditic sandstones of the Carapebus formation (Cretaceous-Tertiary), comprising 80% of the total production. Other important reservoirs are: calcarenites of the Macaé formation (Albian), bioclastic lacustrine limestones of the Lagoa Feia formation (Barremian), and fractured basalts of the Cabiúnas formation (Neocomian). (Fig. 1)

The source rocks are lacustrine saline to brackish water shales of the Lagoa Feia formation (Barremian) containing 5% TOC, an average thickness about 100m with a maximum of 500m in depocenters, covering aproximatelly 50,000 km2.

Trapping style is chiefly structural for the Cabiúnas formation; structural- stratigraphic for the coquinas (bioclastic limestones of the Lagoa Feia formation), where pinch-out of the coquinas is a common feature; strongly structural for the calcarenites of the Macaé formation (rollovers related to salt tectonics), and finally structural combined with sandstone pinch-out for Cretaceous and Tertiary turbidites.

At the depocenters, thermal basin modelling suggests the onset of oil generation in late Albian, reaching its maximum during the Miocene and it is still going on to present days. The top of oil window is about 4,500m deep and transformation rates reaches up to 70%.

The events chart register the temporal relationship between elements and processes of the Lagoa Feia-Carapebus (!) petroleum system in the central area of the basin, responsable for the Marlim oil field charging. (Fig. 2)

The success for oil exploration in the Campos basin results from the presence of excellent source rocks and reservoirs, late migration, presence of internal structural highs, but mostly for the commitment to face deep water exploration challenges.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil