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CRUMEYROLLE, PHILIPPE, Total Research Center, St Remy les Chevreuses, France, DOMINIQUE CLAUDE and JEAN-LOUIS LESUEUR, Elf-Aquitaine, Pau, France, and PHILIPPE JOSEPH, Institut Francais du Petrole, Rueil-Malmaison, France

ABSTRACT: The Roda Deltaic Complex (Spain): Reservoir Stratigraphy of a Low Stand Prograding Wedge

The Eocene Roda sandstones outcrops have been studied in order to better understand the geometry, the internal architecture and the stratigraphy of a low stand deltaic complex. The Roda sandstones are formed by several seaward prograding, vertically stacked and finally landward stepping sandbodies (X, Y, Z). Each sandbody is 10 to 40 m thick and corresponds to three main facies associations:

(1) landward, braided distributary channels together with wave-reworked mouthbars constitute a braided fan-delta.

(2) in a seaward direction, high angle (X sandbody) or low angle (Y sandbody) avalanching foresets up to 15 m thick form several laterally stacked bars which are interpreted as tide-reworked Gilbert-type delta-front bars.

(3) in the seaward part of the Y sandbody, tidal facies become volumetrically much more important. They form a system of tidal offshore bars attached to the shoreface. The thickness and the relative percentage of deltaic facies versus tidal facies are strongly related to the position of the sandbodies in the stacking hierarchy: tidal facies dominate in vertically stacked cycles in a seaward position, whereas deltaic facies are more volumetrically important in seaward stepping cycles such as X sandbody. Three main types of bounding surfaces have been recognized: these are downlap, erosion or flooding surfaces, which also occur within progradational clinoforms. These master bedding surfaces furnish a key in order to establish a precise stratigraphic frame and subdivide each of these pot ntial sandy reservoirs into several subunits bounded by permeability barriers.

(This poster deals with the results of a long-term reservoir research project shared between Elf-Aquitaine, Total and I.F.P. with a financial support of the E.E.C.)

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.