Integrated high-resolution 3D seismic and Gravity-Magnetic modeling for frontier exploration in the northern sector of the Peniche Basin

Abstract

The deep-water Peniche Basin, located along West Iberia’s proximal margin, has been one of the exploration focus area on the southern North Atlantic, especially during the last decade. The basins of the West Iberia Margin have been broadly compared to other hydrocarbon prolific conjugates, such as the Jeanne d’Arc and Flemish Pass, Porcupine and Rockall Trough, and the Essaouira/Aaiun-Tarfaya basins. Still underexplored, with lack of proper stratigraphic control, the northern sector was recently surveyed with a high-resolution, 3200 km2 of 3D seismic and Gravity-Magnetic data. New insights were drawn from these surveys, concerning the interpreted Meso-Cenozoic megasequences inferred from the contiguous Lusitanian and Porto basins. Yet, some lithological variations are expected, reflecting the continuous basinward deepening from the rift-climax phase onwards, and an overall sedimentary infill higher than recorded in the Lusitanian Basin. The opening of the trough between the Porto Seamount and the Aveiro Fault seems to be mostly controlled by tectonic subsidence, associated with a conjugated horizontal and vertical pairing between the deeply-rooted ENE-WSW Aveiro Fault and the NE-SW structures. Its main rotation phase is linked with the rift-climax phases during the Late Jurassic to Early Cretaceous, probably as an effect of relative local crustal thinning. Potential field data modeling was incorporated into the assessment, helping to identify the main structural families and showing the character of each anomaly integrated with regional geology. This provides some insights on the nature and geometry of the Pre-Mesozoic basement within the study area, including apparent local emplacement of Late-Hercynian granitoids. Here we present some results from interpretation of the 3D volume, mapping the main horizons, from sea-floor to near-top basement, identifying salt pillows and diapirs, and discussing their control on Early Cretaceous channel features. Autochthonous salt acts as a regional stratigraphic marker, where in restricted regions a thick pre-salt sequence, likely to be Late Triassic continental siliciclastics, can be observed. Additionally, post-salt Early-Middle Jurassic sag carbonates were also interpreted. Based on our analysis, thick Upper Jurassic wedge sequences are developed within the hanging-walls of the Porto Seamount horst feature and the Aveiro Fault, which can imply local discrepancies in the margin’s rifting evolution prior to continental breakup. Based on regional, proven petroleum system elements and conjugate analogs, source-rocks were defined, and thermal modeling was performed. According to the margin’s estimated thermal regime, supported by Heat Flow measurements recorded in the area, preliminary modeling results point out for mature and overmature source-rocks, which have already reached its maximum oil expulsion potential. These results, coupled with regionally integrated 3D interpretation, enrich both geological knowledge and petroleum potential in the Peniche Basin.

AAPG Datapages/Search and Discovery Article #90325 © 2018 AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin, Lisbon, Portugal, May 2-3, 2018