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AAPG Bulletin


DOI: 10.1306/07151917381

Tectono-sedimentary evolution and petroleum systems of the Mundaú subbasin: A new deep-water exploration frontier in equatorial Brazil

Narelle Maia de Almeida,1 Tiago M. Alves,2 Francisco Nepomuceno Filho,3 George Satander Sá Freire,4 Ana Clara Braga de Souza,5 Márcio Nunes Normando,6 Karen M. Leopoldino Oliveira,7 and Thiago Henrique da Silva Barbosa8

1Programa de Pós-Graduação em Geologia, Universidade Federal do Ceará (UFC), Fortaleza, Ceará, Brazil; Instituto Federal do Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil; [email protected]
23D Seismic Lab, School of Earth and Ocean Sciences, Cardiff University, Cardiff, United Kingdom; [email protected]
3Departamento de Física, UFC, Fortaleza, Ceará, Brazil; [email protected]
4Programa de Pós-Graduação em Geologia, UFC, Fortaleza, Ceará, Brazil; [email protected]
5Programa de Pós-Graduação em Geologia, UFC, Fortaleza, Ceará, Brazil; [email protected]
6Programa de Pós-Graduação em Geologia, UFC, Fortaleza, Ceará, Brazil; [email protected]
7Programa de Pós-Graduação em Geologia, UFC, Fortaleza, Ceará, Brazil; [email protected]
8Departamento de Engenharia do Petróleo, UFC, Fortaleza, Ceará, Brazil [email protected]


The Brazilian equatorial margin (BEM) evolved in response to transform motion between Brazil and Africa. In 2012, Petrobras drilled the Pecém well in the Mundaú subbasin (Ceará Basin) of the BEM to record the first deep-water oil discovery in the region. This work investigates the deep-water evolution of the Mundaú subbasin focusing on its structural and sedimentary evolution, and characterizes the petroleum systems in this new exploration frontier. For such purposes, poststack seismic reflection, borehole, and geochemical data were used. Three tectono-stratigraphic sequences representing synrift (Mundaú Formation), transitional (Paracuru Formation), and drift strata (Ubarana Formation) were divided into seven seismic units. Different tectonic domains were interpreted: proximal, distal, and Romanche Fracture Zone. Typical structures of transform margins, such as marginal ridges and marginal plateaus, were not identified in the Mundaú subbasin. Instead, the subbasin was predominantly deformed by transtensional movements. The Mundaú and Paracuru Formations are mature within the oil window, whereas the Ubarana Formation is immature. Main reservoir intervals consist of approximately 1-m (∼3.28-ft)-thick intercalations of sandstone between shales, siltstones, and marls. The seal rocks comprise shales in the Ubarana Formation, whereas the hydrocarbon trap is related to an unconformity and a normal fault. This work concludes that the Paracuru Formation is the main source and reservoir in the deep-water Mundaú subbasin, effectively comprising a Paracuru–Paracuru petroleum system. The results have significant implications for petroleum exploration in the BEM by proposing a developed transitional petroleum system in the distal parts of northeastern Brazil.

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