--> Abstract: Tectono-Stratigraphic Evolution of a Deep-Water Lowstand Sequence Set and Controls from Reservoir Architecture: Ainsa Basin (Eocene), Spain, by Vitor Abreu, Rob Hill, Jake Violet, Matt Grove, Richard Lovell, and Kirt Campion; #90082 (2008)

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Tectono-Stratigraphic Evolution of a Deep-Water Lowstand Sequence Set and Controls from Reservoir Architecture: Ainsa Basin (Eocene), Spain

Vitor Abreu, Rob Hill, Jake Violet, Matt Grove, Richard Lovell, and Kirt Campion
ExxonMobil, Houston, TX

Deep water rocks exposed in the Ainsa Basin provide excellent analogs to offshore West Africa reservoirs. These outcrops offer an opportunity to characterize the spatial and temporal distribution of reservoir and non-reservoir facies in deep-water deposits, the hierarchical organization of deep water systems, and the development of deep-water systems as part of the basin-scale stratigraphic evolution.

The Ainsa Basin was formed due to the interaction of the African plate with the European plate and Iberian micro-plate during the Cenozoic. Fill in the basin consists of a series of composite sequences that are bounded by angular unconformities resulting from thrust-induced over-steeping. During the Middle Eocene, a Composite Sequence is defined by four deep water depositional sequences: Gerbe-Banaston, Ainsa, Morillo, and O Grau. These depositional sequences stacked to form a lowstand sequence set that is capped by a maximum flooding surface, separating these sequences from the overlying highstand deposits of the Sobrarbe Deltaic Complex.

Stratigraphic stacking, stratal architecture and lithofacies associations were used to interpret deep water depositional environments for each unit and place them in the context of the overall basin evolution. For example, the Gerbe-Banaston sequence is characterized by a rich lithofacies assemblage with relatively short bed lengths that are interpreted as high-energy, confined slope channels developed during the early phases of the cycle. Towards the end of the lowstand sequence set, the O Grau sequence exhibits a more limited lithofacies assemblage with bedsets showing broad aspect ratios that are interpreted as weakly confined to distributive depositional environments in a low-gradient basin. The range of depositional elements present in these outcrops reveals important sub-seismic architectures that may influence fluid flow.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery