AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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Unlocking the exploratory potential of the Pernambuco-Paraíba Basin, Brazil: Multiphased rifting and thermal modeling on a salt-influenced basin

Abstract

The Pernambuco-Paraíba Basin (PEPB) lies in one of the last poorly-known deep-water areas of the NE Brazilian rifted margin, and has been recently evaluated in petroleum exploration. The PEPB is bounded in the distal eastern edge by the Pernambuco and Touros Plateaus, which are related with rift and (mostly) post-rift volcanic phases. The structural domain is bounded to the north by a NW-SE transform margin, and to the south by the Maragogi High. The upper crustal domain is characterized by half-graben faulted blocks to rotated ones on the easternmost distal part, with NE-SW listric faults combined with NW-SE oblique transfer faults. Only three wells were drilled in the vicinity of the basin, which don’t supply sufficient stratigraphic information. Nevertheless, the available 3D seismic revealed the apparent basement position, extensional-related structures, and two marine syn-rift packages established in the main graben. It also shows remarkable salt growth, which frequently crosses the syn-rift sequences and appears to control marine depositional systems during the Albian. Salt diapirs not only controlled the Albian channels and fan features – considered to be the main reservoirs – but also promoted wide-angle anticline traps at a later stage, most likely related with the Upper Cretaceous-Tertiary post-breakup tectonic reactivations. Petroleum systems modeling was carried out to address the prospectivity of the study area, considering two hypothetical oil-prone marine source-rocks charging hydrocarbons into the Albian reservoirs. A thermal model was built accounting for two rifting phases that were identified in seismic, and calibrated using regional assumptions from the adjacent Sergipe-Alagoas Basin. It accounted for the Albian post-rift volcanic phase that is identified mostly on the distal basin edge, where rift hinges were reactivated and uplifted (Caixeta et al. 2014) before late-breakup thermal subsidence from the Cenomanian-Turonian onwards. Preliminary results for different temperature scenarios show there is maturity and oil expulsion potential towards the Albian reservoirs and subsequent Upper Cretaceous sequence, with minor gas expulsion. Charge timing for a base case reference model also seems to be encouraging, as peak oil expulsion would have occurred after salt-related trap formation.