Análise estratigráfica das seções rifte e pós-rifte na Sub-bacia de Mundaú da Bacia do Ceará, Margem Equatorial Brasileira

Abstract

The discoveries of oil fields in the African Equatorial Margin combined with the drilling of wells such as Pecém and Pitu, respectively, in the Ceará and Potiguar basins, reinforce the necessity for studies which aim to better understand the evolution of the sedimentary basins within the Brazilian Equatorial Margin, emerging as a new frontier for hydrocarbon exploration. The tectonic-structural complexity of the Brazilian Equatorial Margin is discussed in several works, which classify this region as a transforming passive margin. However, there is a gap in the research of this basins when it comes to the concepts of Sequence Stratigraphy. The Ceará Basin is placed in the continental shelf of the Brazilian Equatorial Margin and its origin is connected to the Gondwana’s breakup process during the Early Cretaceous, resulting in the Equatorial Atlantic opening. The basin is limited to the southeast by the Fortaleza High, to the west by the Tutóia High, to the north by the southern part of the Zomanche Fracture Zone, and to the south by the crystalline basement. Due to the distinct tectonic aspects and different structural framework, The Ceará Basin can be divided into four sub-basins, from west to east: Piauí-Camocim, Acaraú, Icaraí and Mundaú. The stratigraphic framework of the Mundaú Sub-basin is composed by three super sequences: rift, post-rift and drift. In lithostratigraphic terms, the rift and post-rift stages correspond to the Mundaú and Paracuru formations, respectively. They were studied in this work from the well data, allowing the elaboration of 1D diagrams, with lithofacies, cycles, cycle sets and depositional sequences. The seismic stratigraphic analysis was carried out from 2D seismic lines, and consisted of characterizing seismic facies and the identification of reflectors terminations, culminating in the recognition of sequence stratigraphy units and surfaces. The integration of this interpretations allowed the separation of the studied section in terms of seismic stratigraphic units, which were associated with tectonic systems tracts. At the end, it was possible to propose a model for the tectono-stratigraphic evolution of the studied sub-basin.