The Salt Layer as Important Key to the Pernambuco Plateau Petroleum System, NE Brazil
The Pernambuco Basin (PEB) represents a marginal basin with an area of approximately 20,800 km² located in the eastern portion of Northeast Brazil. This basin represents one of the most prominent exploration frontiers in the deep waters of the Brazilian margin. Piston core campaign performed in 2005 revealed the existence of an active petroleum system, with a few discoveries of oil exudations in the plateau region. These exudations can be related to structures associated with a regional evaporitic layer, which deformation created oil migration pathways. We performed a study of this salt layer that covers the Pernambuco Plateau. The lack of offshore wells prevents the confirmation of nature and age of this salt basin. The study was based in the investigation of 132 2D time-migrated seismic sections that covers the offshore region of PEB, and 2D geophysical transects built with satellite-based gravimetric data and airborne magnetometric data. The results allowed estimating the distribution, and the main characteristics of this salt layer (thickness and salt-related structures). PEB presents two rift stages - Barremian?-Aptian, and Lower-Middle Albian. Stratigraphic relations revealed that the salt layer was deposited in Late Aptian, which implies that it was affected by late rifting processes. According to that prospect, the salt layer was early deformed by active rift faulting (tilted and folded), which strongly influenced salt tectonics during the evolution of burial across Late Cretaceous to the Present. Early deformation stages of the salt layer during the rift influenced the geometry of its post rift deformation, when the salt formed salt sheets that intruded post-rift and drift successions (allochthonous salt sheets). Other structures like large salt diapirs and salt drops were formed mainly over the depocenters. Salt deformation patterns in regional scale show good correlation with the depocenters borders, and with location of oil exudation, which are of critical importance to modeling of the PEB Petroleum System.
AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019