--> --> Petroleum Systems and Thermal Modeling of the Western Iberian Margin – From the Onshore Lusitanian Basin to the Deep Offshore Peniche Basin

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Petroleum Systems and Thermal Modeling of the Western Iberian Margin – From the Onshore Lusitanian Basin to the Deep Offshore Peniche Basin


The Lusitanian Basin is one of the Western Iberian Margin's basins, all related with the opening of the North Atlantic and having their counterparts in eastern Canada's Jeanne D'Arc and Whale Basins. In the Lusitanian Basin, pre-rift, rift and drift phases, with its associated deposits, may be studied in detail, including a whole range of lithofacies, from continental proximal infills to distal deep-marine condensed sections. In addition, the structural style and the importance of basement, diapiric structures and other evolutionary aspects can also be investigated. This paper deals with the sedimentary and thermal evolution of the mainly onshore Lusitanian Basin and its petroleum systems, establishing an analogue for the nearby offshore Peniche Basin, aiming to contribute to a better regional framework for exploration in this region. Petroleum systems of the Lusitanian Basin are well known from outcrops and wells, with abundant data about the elements and processes of its petroleum systems. In the Peniche Basin, a seismo-stratigraphic approach, based on the analysis of 28 seismic lines (courtesy of PETROBRAS), allowed the identification of broadly the same sedimentary packages and some extrapolation about its petroleum systems. Subsidence and thermal maturation modeling (PetroMod) has been conducted on 10 wells of the Lusitanian Basin and 13 pseudo-wells of the Peniche Basin. A comparative analysis shows that both Jurassic potential source rocks - marine lower Jurassic shaly marls and lagoonal upper Jurassic marly limestones - reached oil-window in both basins. The lower SR entered the oil-window between late Jurassic and early Cretaceous times, whereas the upper SR entered the oil-window mainly in late Cretaceous to early Tertiary times. However, some lateral variations may be identified in regional maps, related with the inner/outer position of each basin, as well as with each basin's depocenters. Several thick reservoirs, including late Cretaceous and Tertiary siliciclastics, may have accumulated oil, migrated along faults and diapiric structures, related with Mesozoic extension and also with alpine compression. These reservoirs are well sealed by clayey units, expected to thicken distally towards the outer basins. Alpine inversion structures may have promoted good trap geometries, but also seriously affected seal-integrity. All these interpretations are still to be validated by a wildcat well, constraining stratigraphic and thermal assumptions.