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Integrated Workflow for Characterization and Modelling of a Mixed Sedimentary System: The Ilerdian Alveolina Limestone Formation (Early Eocene, Graus-Tremp Basin, Pyrenees, Spain)

Hamon, Youri *1; Deschamps, Remy 1; Joseph, Philippe 1; Schmitz, Julien 1; Doligez, Brigitte 1
(1) Sedimentology-Stratigraphy, IFPEN, Rueil-Malmaison, France.

Reservoir properties are controlled primarily by the sedimentary architecture and facies distribution but are strongly modified by the early to late diagenetic history. The understanding and the spatial prediction of the reservoir heterogeneities induced by the diagenesis is thus a crucial question for reservoir characterization and modelling.

The aim of this paper is to propose an integrated approach to highlight the sedimentary and stratigraphic factors that control the spatial distribution of diagenetic phases in a mixed siliciclastic-carbonate succession. Based on this study, a fine grid geological model was built to reproduce both the sedimentary facies and the diagenetic trends interpreted from outcrop observations.

In the Graus-Tremp Basin, the Ilerdian (early Eocene) Alveolina Limestone Formation is clearly a mixed carbonate-siliciclastic series, showing a complex pattern of bioclastic, bioconstructed and clastic facies.

At a regional scale (Graus-Tremp basin), sedimentological sections were described and sampled. Several lithofacies have been described and grouped in facies associations attributed to a specific depositional environment on the basis of their constituent facies, packaging patterns and overall geometry: proximal deltaic complex, shallow inner-ramp, mid-ramp, mid- to outer-ramp, filling of incision, coral-dominated patch reef, reef-mound. This study allows the construction of a detailed paleogeography based on sequence stratigraphy analysis for the Early Ilerdian series of the Graus-Tremp Basin.

Subsequently, a focus at reservoir scale has been realized for reservoir architecture and diagenetic modelling. A 3D conceptual model illustrating the depositional architecture of the Serraduy area is also proposed based on the sedimentary geometries assessed on the field. Results from the diagenetic study (petrography and geochemistry) show the occurrence of several successive early (micritization, marine calcite cementation, dissolution, neomorphism) and late (calcite cementation, compaction features) diagenetic phases.

The 3D gridded model has been constructed, based on nine surfaces (sequence boundaries and maximum flooding surfaces) helped by 3D outcrop model (3D photogrammetry).The relationships between sedimentary facies and diagenesis have been used to define lithofacies simulation rules for the plurigaussian algorithm, that aims at simulating both the distribution of sedimentary facies and the diagenetic overprint.


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California