Assessing the hydrocarbon potential of the Peniche Basin, offshore Portugal
The Peniche sedimentary basin is part of the West Iberia and Newfoundland conjugate margins system, considered a magma-poor passive margin (Franke, 2013) situated in the deep Atlantic Ocean offshore Portugal. It encompasses an area of about 24000 km2 within which no exploration wells has been drilled. Wells located in the shelf domain of the Lusitanian basin (east of Peniche basin), DSDP/ODP wells (located west of the basin), vintages of 2D seismic, a 3D seismic cube and gravity and magnetic data have been used to assess the petroleum potential of this unexplored basin.
The geological evolution of the basin can be divided into four main episodes of rifting, that resulted in the break-up of Iberia and Grand Banks; 1) Triassic, 2) Sinemurian – Plienbachian, 3) Late Oxfordian and 4) Early Cretaceous. Followed by final break-up and seafloor spreading that started in Berriasian in the South Tagus Abyssal plan migrating northward across the Charlie Gibbs fracture zone in the Early Albian. The Peniche and adjacent Lusitania basins are separated a N-S trending structural high (Alves et al. 2006).
Though no well have been drilled in the Pencihe basin, some Lusitanian offshore wells have hydrocarbon shows, indicating the presence of an active petroleum system in that basin. Three potential Mesozoic source rock intervals were encountered in the wells : the Lower Jurassic Sinemurian and Pliensbachian, are considered as the principal source rock in the northern Lusitanian basin, while the oils present in the southern part seems to come from the Late Jurassic, i.e. Oxfordian source rock.
Several levels of siliciclastic and carbonate reservoirs were deposited during the periods of rifting and seafloor spreading. These levels of reservoir (and source) rocks has been encountered in the shelf wells of the Lusitania basin and traced on seismic to the Peniche basin.
The halokinesis that accompanied the deposition of post salt sediments, as well as the basin inversion associated with the convergence of Iberia, Eurasia and Africa has created structural, stratigraphic and combined traps that can accommodate tremendous quantities of hydrocarbons similar to fields found in the conjugate basins of Newfound Land. Petroleum system modelling indicates that the source rocks are mature for oil and could have migrated into the created traps.
Thus integrating regional geology, seismic interpretation and well correlation, data in conjunction with Lusitania basin outcrop and shelf well postmortem analysis has enabled the Peniche project exploration team to infer the possible existence of several working petroleum systems in the basin with significant hydrocarbon potential.
AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015