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Abstract: Sand Body Geometry and Permeability Areal Distribution in Fluvial Sandstones Reservoir

A. Francesconi, M. Erba, A. Puliti, M. Rampoldi

This paper describes as the integration between geological and reservoir engineering activities led to a more accurate detection of permeability areal distribution in a giant oil field where depositional environment retains a fundamental control on reservoir petrophysical characteristics.

The data source was: well-log and well-test data of 60 wells, laboratory analyses and sedimentological studies of about 10 fully cored wells, more than 20 years of field performance.

The sedimentological study pointed out the presence of three non-marine environments: low-sinuosity braided channel, overbank splay and flood basin. The areal distribution of these environments was controlled by the synsedimentary tectonic movement.

Permeability/porosity correlations were investigated on the basis of core data and the continuous permeability profile was estimated. Based on these data the arithmetic, geometric and harmonic average were calculated to investigate the flow characteristics of the individual reservoir units by comparing the log permeability with the well-test permeability assumed as the reference value.

The results of this comparison led to a further analysis of the sedimentological and electrofacies data.

The following conclusions were drawn: the areas characterized by the arithmetic average correspond to over bank splay environment where low permeable sandstones with high lateral continuity sedimented; the areas characterized by the geometric and harmonic average correspond to channel environment where more permeable sandstones with poor lateral continuity sedimented.

The permeability maps, optimized according to these sedimentological concepts, gave a fundamental improvement to the history match process.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France