--> Abstract: Accommodation: Sediment Supply Ratio (A/S) a key parameter for Stratigraphic Modeling and Reservoir Architecture Prediction, by J. C. Navarre and M. Bez; #90942 (1997).

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Abstract: Accommodation: Sediment Supply Ratio (A/S) a key parameter for Stratigraphic Modeling and Reservoir Architecture Prediction

NAVARRE J.C. and M. BEZ

Stratigraphic models predict the range of possible stratigraphic geometries and facies distributions between well control. The input parameters (including tectonics, eustasy and sediment supply) are constrained by the stratigraphic record derived from well log, core or field data. This stratigraphic record is best interpreted and modeled using one main parameter, A/S ratio.

Surface and subsurface strata within the Mesa Verde Group (Upper Cretaceous), San Juan basin (Colorado) are subdivided into stratigraphic cycles of at least three temporal scales. All scales of cycles record oscillations of base-level and concomitant variations of increasing and decreasing A/S ratios. Cycle symmetry, stratigraphic architecture, facies assemblage and sediment preservation, between coastal-plain and shoreface strata, are function of their position in the long-term base level cycle. During long-term base-level fall hemicycle, in low accommodation settings:

- Intermediate-term cycles in coastal plain strata are represented by crevasse splay/crevasse channel deposition and an erosional surface of unconformity formed during base-level fall hemicycles and an accumulation of amalgamated channelbelt sandstones on top of the unconformity surface during base-level rise hemicycles.

- Intermediate-term shoreface cycles are recognized by changes in the aggradation to progradation ratio and are composed of heterogeneous sandstones.

During long-term base-level rise hemicycle, in high accommodation settings:

- Intermediate-term cycles in coastal plain are symmetrical. The base-level fall hemicycle consists of a gradual filling of lakes. During base-level rise hemicycle, facies successions are opposite and record gradual flooding of the floodplain.

- Intermediate-term shoreface cycles are generally base-level fall asymmetrical and composed of homogeneous sandstones.

Knowledge of these facies changes within a stratigraphic context is an invaluable aid to predict geometries and facies distributions. Consequently, accommodation curves based on stratigraphic cycles stacking pattern and facies interpreted in bathymetry value are essential for correlation and reservoir models.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria