--> Abstract: Offshore Algarve Basin, Portugal: Morphology of Paleozoic "Basement" and Influence on Mesozoic Sedimentation, by Hugo C. Matias, Frode Sandnes, Valeria C. F. Barbosa, P. T. L Menezes, Reidun Myklebust, Luis M. Matias, and Fernando A. Santos; #90039 (2005)

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Offshore Algarve Basin, Portugal: Morphology of Paleozoic "Basement" and Influence on Mesozoic Sedimentation

Hugo C. Matias1, Frode Sandnes2, Valéria C. F. Barbosa3, P. T. L Menezes4, Reidun Myklebust5, Luis M. Matias1, and Fernando A. Santos6
1 Faculty of Sciences - University of Lisbon, Lisboa, Portugal
2 TGS, N-3478 Naersnes, Norway
3 Research Scientist in Geophysics, Petrópolis, Brazil
4 DGAP/FGEL/UERJ, Brazil
5 TGS,
6 University of Lisbon,

The Algarve Basin developed as an extensional basin in the Mesozoic, and a thick sedimentary succession (consisting of continental clastics, two evaporite series, carbonates and marine clastics) was deposited. The basin was subsequently deformed by NW-SE transtensional and compressional stresses along the Azores-Gibraltar Fracture Zone. This deformation coupled with halokenesis, makes it difficult to map Paleozoic “basement” accurately. None of the five wells drilled in the basin penetrated the entire Mesozoic succession.

Interpreting the relief of the Paleozoic “basement” is important for predicting the Mesozoic depositional history and patterns. The interpretation is aided by 3D gravity inversion of data recorded along regional seismic profiles (acquired in a 4 km by 8 km grid). The gravity inversion algorithm utilized is the first-order Tikhonov regularization method.

Integrated gravity and seismic interpretation has resulted in a better understanding of the basin and its hydrocarbon potential. The Algarve Basin is delimited to the south by a basement high with a NE-SW orientation (Guadalquivir Bank). The basin strikes around ENE-WSW direction with the main depocenter striking E-W and a maximum depth of approximately 9 km. The Mesozoic succession accounts for some 6 km of the basin fill. Some terraces associated with horsts and grabens were correlated with regional faults that extend onshore. Carbonate banks and potential basinal source rock facies have been outlined. Sand rich siliciclastic depositional systems are also predicted. A live thermogenic petroleum system is substantiated by satellite detected oil seeps and an oil stained dredge sample.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005