Stratigraphic Analysis of the Cretaceous Turbidite Reservoirs in the Campos Basin, Brazil

Eduardo G. Barboza, Ricardo N. Ayup-Zouain, and Maria Luiza C. C. Rosa
UFRGS, Porto Alegre, Brazil

This work deals with the geometry and genesis of the Cretaceous turbidite reservoirs in the Campos Basin, Brazil. An alternative evolution model for this field in the interval Upper Albian to Cenomanian is presented.

A three-dimensional seismic interpretation with VoxelGeo® software and facies analyses using well log profiles data are applied to this study. These provide the necessary constraints to identify and obtain a three-dimensional visualization of a sinuous paleochannel at the base of the interval studied. This paleochannel has not been visualized by the earlier interpretations of this reservoir.

In addition to the seismic and facies analyses, a depositional model is developed with four distinct turbidite systems in two 3rd order sequences. These turbidite systems are therefore associated with 4th order sequences, which are interpreted as parasequences, as part of the two cycles in the 3rd order sequence. The 3rd sequences that contain the reservoirs, represent high frequency intervals in the stratigraphic record, in a drowning context (2nd order) of the Campos Basin.

Based on the characteristics observed in the depositional system, it is assumed that a channel complex arrangement for the whole system was developed. These channels were formed by hyperpicnal fluxes, after catastrophic inundations at the deltaic front system.

The data presented herein provide a more advanced model and understanding of the genesis of hydrocarbon accumulation in the studied interval, mainly in the turbidite deposits, whose occurrences are related to stages of relative lowering of sea level.