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ABSTRACT: The Discovery History and a Depositional Model for the Reservoir Rocks of the Marlim Field--Campos Basin, Brazil

W. E. Peres, L. R. Guardado

The Marlim field is located in the Campos basin, approximately 100 km offshore of Rio de Janeiro State, Brazil. The basin was discovered early in 1985 by the wildcat 1-RJS-219, drilled in a water depth of 853 m. Its areal extent is 152 km2, and its latest estimate of oil in place is about 8.2 billion bbl.

The first steps toward this discovery were taken when a seismic amplitude anomaly was identified in two-dimensional seismic data and a wildcat was proposed for the westernmost edge of the seismic anomaly, where the well could also reach a prominent Cretaceous structural high.

The interpretation of new seismic data resulted in a better definition of the seismic amplitude anomaly limits, indicating that the anomalous reflection could represent a relatively thick, sand-rich turbidite complex. This new interpretation allowed a better positioning of the undrilled exploratory well, where a 75-m-thick sandstone was found.

The Marlim Complex reservoir rocks were deposited mainly during the major Oligocene relative sea level fall by a dominantly progradational process. This sea level fall exposed the late Eocene/early Oligocene sand-rich deposits of the Sao Tome low to the action of predominantly subaqueous erosive processes on a shallow shelf.

Halokinesis apparently was the major mechanism that led to sediment failure at the delta front of the former wave-dominated Paraiba do Sul delta system, originating the turbidite currents that were the main processes for canyon excavation and sediment transport from the shelf to deep-water environment.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990