NORRIS, RICHARD J., and G. MASSONNAT, ELF Aquitaine Production, Pau, France

ABSTRACT: The Impact of Geological Interpretation on Stochastic Reservoir Modeling and Flow Simulation

For a field in its appraisal stage (less than ten wells), stochastic reservoir modeling and flow simulation have been used to optimize a field development plan and to quantify uncertainties. Prior to sensitivity studies, a base-case geological model was developed, this however, proved to be surprisingly difficult. A study of the within-reservoir heterogeneities was undertaken during which the interpretation of seismic expression as geological features was seen to be very significant.

Seismic interpretation of a submarine canyon-fill revealed three discrete "packets" of sediments. Each packet has a distinct seismic expression which is associated with assemblages of facies interpreted from well data. Two geological models can be invoked to explain the sedimentological history of the canyon-fill. In the first case, the boundaries between packets represent time-lines; in the second case, the packets are contemporaneous, being longitudinal facies-changes. The geological models will clearly be different; moreover, the associated geostatistical models differ considerably. In the first case (time lines), the three reservoir zones are modeled independently, with the boundaries compartmentalizing the reservoir. In the second case, the facies grade into one another, ensuring connectivity between the zones. Likewise, continuity of, and relationships between facies will be different in the two cases.

The dynamic reservoir properties are shown to be critically dependent upon the original choice of geological model.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.