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Extending the Reservoir Facies Beyond the Classic Exploration Model for Microbial Carbonates: Looking For New Opportunities in Campos Basin, Brazil

Daudt, J.; Louzada, Carlos1; Bondurant, C.; Blevins, M.; Chong, G.; and Walton, Gene
1[email protected]

The giant oil accumulations recently discovered in the pre-salt section of the Campos and Santos basins created an exciting scenario for offshore exploration in Brazil. These discoveries in the pre-salt reservoirs have caused a drastic change in the Brazilian reserves profile as deep water turbidites used to represent more than 85% of the total number in 2007 (estimated by that time in 14 billion of boe, excluding sag carbonates). Today, the Santos and Campos pre-salt plays have potential resources of more than 50 billion barrels. However, there is a huge uncertainty in these numbers mainly due to the limited well control, seismic data of variable quality, and scarce dynamic data.

As the exploration of these carbonates intensified in the past 5 years, new data was acquired and new insights were gained. Studies led by several universities on modern analogues have been increased in number since the pre-salt "boom" in Brazil. Relying on the Huttonian concept that "the present is the key to the past", these studies bring perceptions from the present day counterparts that help to reveal the key aspects of the evolution of the ancient Aptian lakes. In this sense, they must incorporate a comprehensive understanding of the tectonic evolution of the lakes, their water chemistry variability, and climate influence on the carbonatic facies stratigraphy. Unfortunately, it was observed that there is no perfect analogy that can be simplistically applied to the pre-salt section.

In order to create a predictive depositional model to guide exploratory efforts in these carbonates, some specific questions need to be addressed. For instance, what is the influence of paleo-topography on the distribution of the high energy facies? What is the impact of base level variations and lake compartmentalization on stratigraphic evolution? What is the role of marine incursion events in the preservation and distribution of sag reservoirs? What is the importance of the stratigraphic edges in defining the sag carbonate play? With these questions in mind, this presentation will discuss several concepts and models with emphasis on the stratigraphic component. The intention is to debate aspects related to the potential of finding good reservoir facies beyond the classic carbonatic model, creating new exploratory paradigms. These ideas may open new opportunities for exploring sag carbonates in the Campos Basin.

 

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013