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Reservoir Characterization and Geostatistical Modeling of an Eolian Reservoir for Simulation, East Painter Reservoir Field, Wyoming

SINGDAHLSEN, D. S., Chevron U.S.A. Inc., Denver, CO

The East Painter structure is a doubly plunging, asymmetric anticline formed on the hanging wall of a back-thrust imbricate near the leading edge of the Absaroka Thrust. The Jurassic Nugget Sandstone is the productive horizon in the East Painter structure. The approximately 900-ft-thick Nugget is a stratigraphically complex and heterogeneous unit deposited by eolian processes in a complex erg setting.

The high degree of heterogeneity within the Nugget results from variations in grain size, sorting, mineralogy, and degree and distribution of lamination. The Nugget is comprised of dune, transitional toeset, and interdune facies, each exhibiting different porosity and permeability distributions. Facies architecture results in both vertical and horizontal stratification of the reservoir. Dune set orientations within the Nugget control directional permeability trends in the reservoir. Facies discontinuities, fractures, and faults offset the permeability trends in parts of the field.

Adequate representation of reservoir heterogeneity is the key to successful modeling of past and future production performance. In addition, a detailed geologic model, based on depositional environment, must be integrated into the simulation to ensure realistic results. Geostatistics provide a method for modeling the spatial reservoir property distribution while honoring all data values at their sample location. Conditional simulation is a geostatistical technique that generates several equally probable realizations that observe the data and spatial constraints imposed upon them while including fractal variability. Flow simulations of multiple reservoir realizations can provide a probability distribution of reservoir performance that can be used to evaluate risk associated with a proj ct caused by the incomplete sampling of the reservoir property distribution.


AAPG Search and Discovery Article #91010©1991 AAPG Rocky Mountain Section Meeting, Billings, Montana, July 28-31, 1991 (2009)