Carbonate Buildups in the Post-Rift Sequence of the Pernambuco Basin, NE Brazil: Oil Play Implications

Abstract

The Pernambuco Basin (PEB) is a 20,800-km² area located in the eastern continental margin of Northeast Brazil. This basin represents one of the most prominent exploration frontiers in the deep waters of the Brazilian margin, with the best potential residing in the Pernambuco Plateau region. We performed a detailed study of carbonate buildups within the post-rift sequences of the PEB, which provides an important contribution to the Petroleum Potential of this marginal basin. This study is based on an analysis of 143 2D seismic surveys that cover almost the entire plateau region. The methodology included a detailed interpretation of 59 selected time-migrated seismic sections, application of post-processing filters to reduce the n/s ratio, and an additional integrated analysis of potential geophysical surveys to distinguish magmatic extrusive structures that also affect the post-rift sequences. Due to the lack of offshore wells, the age of the main interpreted seismic sequences were based on available data from the onshore region of the PEB and available data from the offshore region of the Alagoas Basin. Thus, four main seismic sections were defined: rift – (Barremian-Albian), Cretaceous post-rift (Albian-Maastrichtian), Lower Cenozoic post-rift (Maastrichtian-Middle Miocene), and Upper Cenozoic post-rift (Middle Miocene-Recent). Carbonate buildups represent structures extending up to 15 km long and up to 0.9 s (TWT) thick. They are abundant in the north and central portions of the Pernambuco Plateau, and were formed over outer structural highs, salt domes, and magmatic buildings. These structures formed from the Late Cretaceous (Santonian?-Maastrichtian) to the Neogene (Miocene). They consist of rimmed and isolated carbonate platforms exhibiting typical progradation wedges related to eustatic cycles, and this interpretation allows for a preliminary sequence stratigraphy analysis for the Cenozoic interval of the PEB. Most of the carbonate buildups are capped by marine shales (seal rocks) and are connected with the deep zones of the depocentres by rift faults (possible migration paths) that were reactivated by post-rift events. Thus, the carbonate buildups of the PEB have important features that point to the potential of these structures as a promising oil play for oil and gas reservoirs, as observed in the southeast Brazilian margin basins. Keywords – Pernambuco Basin, carbonate buildups, oil plays, sequence stratigraphy

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016