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ABSTRACT: Modeling of Bayu-Undan Field

Balke, Scott C., and John C. Currie , Phillips Oil Company Australia, West Perth, Australia

A case study using reservoir characterization with geostatistical modeling to develop high confidence reservoir performance predictions is presented for Bayu-Undan Field. This study shows how the modeling was tailored to both reservoir type and the selected development scenario.

Bayu-Undan Field is currently under development as a gas recycle project with future gas export. The reservoir is made up of both fluvial and marine sedimentary sequences. The major control on reservoir character is facies type which controls grain size, sedimentary structure and degree of bioturbation. Facies were determined from log motif and core description. Different statistical techniques were chosen to build facies models for the continuous marine zones and the heterolithic marine/fluvial zones.

Numerous facies realizations were constructed to evaluate the possible range of outcomes and uncertainties. Porosity was distributed either determinist-ically using a weighted average algorithm or statistically using variograms. Permeability was distributed using a porosity-based transform. Gas saturation was determined by a porosity/permeability/height-above-free-water function derived from Special Core Analysis.

The resulting 283 layer, nine million-cell geocellular model was upscaled to a 19 layer, 35,000 cell reservoir flow simulation model. To ensure reservoir heterogeneity was preserved in the upscaled model, a number of permeability upscaling algorithms were evaluated. As a result, separate algorithms were chosen for horizontal permeability in marine and fluvial units, and for vertical permeability. Use of these upscaling techniques resulted in very good preservation of gas in place by permeability class, shown comparing the geocelluar model with the upscaled model. The modeling captured and preserved the reservoir flow characteristics critical to performance predictions for the gas recycle project.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia