Sequence stratigraphy and the Ubarana-Upper Cretaceous exploratory play within the lower Albian – middle Eocene section of the Mundaú sub-basin, Ceará Basin

Abstract

The Ceará Basin is located at the east portion of the Brazilian Equatorial Margin, and it is subdivided from west to east into four sub-basins: Piauí-Camocim, Acaraú, Icaraí and Mundaú, the latter being the focus of this study. The lower Albian to middle Eocene section of the Mundaú sub-basin is characterized by the Ubarana-Upper Cretaceous exploratory play, with turbidite reservoirs. That same chronostratigraphic interval shows important discoveries on the African Margin, such as the Jubilee field, and on the Equatorial Margin in offshore fields in Guyana and Suriname. For this study, it was used data from eight exploratory wells and ten 2D seismic lines, located on the shelf-edge portion, in shallow waters, to the deep-water region. In this study, six low resolution Transgressive-Regressive sequences were identified. These T-R sequences are bounded at the top and bottom by maximum regressive surfaces (MRS), that were recognized in the well data, and posteriorly in the seismic data, through seismic stratigraphy methods. In addition to the MRS, maximum flooding surfaces (MFS) are recognized in the exploratory wells, through low and high frequency T-R cycles. In addition, this work allowed the identification of turbidite plays in deep waters regions The genesis of those turbidites, defined as the low-density type, is associated with a base-level rise at the shoreline, when the normal regression phase occurs. Thus, this study contributes with stratigraphic description of the lower Albian-middle Eocene section, and identification of turbidite reservoirs within that interval, which are important to the exploration and discovery of hydrocarbons in context in the Brazilian Equatorial Margin.