--> Geoarchitectural Analysis of Forced Regressive Isolated Sandstone Bodies: A New Reservoir Emplacement Model for Devonian Petroleum Systems of Brazil, Young, Charles; Borghi, Leonardo; Denck, Thiago, #90100 (2009)

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Geoarchitectural Analysis of Forced Regressive Isolated Sandstone Bodies: A New Reservoir Emplacement Model for Devonian Petroleum Systems of Brazil

Young, Charles1
 Borghi, Leonardo2
 Denck, Thiago2

1E&P, BG Group, Rio de Janeiro, Brazil.
2
Laboratório de Geologia Sedimentar (Lagesed), UFRJ,
Rio de Janeiro, Brazil.

Isolated sandstone bodies generated during events of forced shoreline regression represent a tried-and-true model for sandstone reservoir prediction in areas such as the Cretaceous of Western Canada and the Lower Paleozoic of the North African sedimentary basins. Such model has yet to be thoroughly tested on Brazilian Paleozoic basins, all which possess similar conditions - ramp-style cratonic basins with epeiric seas. The
Parnaíba Basin, a 600.000 sqkm cratonic basin, located in the Northeastern Brazil, represents one of the least studied Paleozoic areas in Brazil. Its Devonian section, represented by the Itaim, Pimenteira, Cabeças and Longá formations, has been the main focus for petroleum exploration efforts, where potential source-rocks, seals and reservoirs are interpreted as deposited on ancient environments ranging from fluvio-deltaic to storm-dominated shallow seas. Recently, the authors proposed an integrated depositional model for the Devonian of this basin based on cores, logs, palynofacies and outcrops, with special focus on the depositional geoarchitecture of the Pimenteira Formation, whose shales are considered the main source rocks in the basin. As a result, four isolated sandstone bodies (10-20m thick each) with fair reservoirs characteristics were identified within the Pimenteira Formation, all of them deposited in storm-dominated shallow seas with prodeltaic influence. The origin of these sandstone bodies is genetically related to forced regressions events of 4th/5th order, which emplaced potential reservoirs amidst the main source rocks. Some of these sandstone bodies were characterized at outcrop scale (macroscale), allowing the identification of geoarchitectural elements, whose facies and geometries allow a discussion of the reservoir’s quality and connectivity. This model is of special significance for exploration efforts in the Parnaíba basin since it creates the perspective of a new Pimenteira-Pimenteira(?) petroleum system, with a greatly improved chance of effective oil migration, accumulation and sealing. This exploration model remains to be tested in other Brazilian Paleozoic basins, like the Paraná and Amazonas, or even the Solimões Basin, the only current Paleozoic basin with commercial oil and gas production.

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil