Abstract:
Based on well logs, cuttings, cores and 3D seismic this work presents the 3rd order stratigraphic framework of the Feliz Deserto, Barra de Itiúba and Penedo formations and its relationship with the Furado Oilfield reservoir zones (Sergipe-Alagoas Basin). It also discusses the impact of tectonics on sedimentation during the early rifting stages. The J20-K5 Sequence (Candeeiro, Bananeiras and Serraria formations of the Dom João / Rio da Serra stages) comprise mostly shallow lacustrine and fluvial deposits that conformably change upwards to the K10-K20 Sequence (Feliz Deserto Formation of the Rio da Serra Stage), both making up a single 2nd order sequence. The K10-K20 sequences encompass shallow lacustrine facies that record a gradual growth on tectonic activity, as pointed by the upward change from parallel to divergent strata. The Pre-Aratu Unconformity bounds the K10-K20 and K34-K36 sequences and represents an important regional uplift event. A new subsidence pulse resulted in the deposition of the K34-K36 Sequence (Aratú to Buracica stages). Its lower 3rd order sequences encompass lacustrine and deltaic deposits and show evidence of higher-scale lake-level fluctuations relative to the K10-K20 Sequence. The upper 3rd order sequences represent the last stages of basin filling (coarse-grained fluvial deposits), the uppermost being equivalent to the Penedo Formation (Jiquiá Stage). Later, in the Alagoas Stage, a huge number of large, post-depositional normal faults deformed the entire succession although a gentle tectonic activity, related to fault propagation folding, a typical feature of early rifting, is identifiable since the late Rio da Serra Stage.
Keywords:
Sergipe-Alagoas Basin; Feliz Deserto Formation; Barra de Itiúba Formation; Rift