HARA, S. K., D. W. HILL, and R. M. JOHNSTON, Shell Western E&P Inc., Bakersfield, CA
ABSTRACT: Shell's Diatomite Field Study; Part I: Characterizing an Extremely Variable Reservoir; Part II: Modeling for Redevelopment, Forecasting, and Surveillance
Shell's Belridge Diatomite holdings exceed 3 billion stock tank bbl of oil in place. The reservoir exhibits low permeability in a thick, highly layered formation. A complex structural and diagenetic history has resulted in extreme variations in lithology, saturation, and other reservoir properties. A multiple charge history has led to a field-wide oil gravity distribution ranging from 10 to 34 degrees API.
The extreme variability in reservoir properties is reflected in the production performance of different areas of the field and different layers of the reservoir. Only by incorporating our new understanding of this variability have we been able to analyze the performance of the initial primary wells, the ongoing waterflood projects, and tests of steam-drive and steam-soak potential. Using models which explicitly incorporate reservoir heterogeneity, we have developed surveillance tools to assist in the optimization of the existing projects and plans for the implementation of new projects and processes which are tuned to different areas of the field.
Models for many different areas of the field have been generated which incorporate explicit thickness, saturation, porosity, and oil gravity values and inferred absolute permeability and relative permeability in as many as 28 layers. Several models also incorporate induced fracture process zone realizations, fracture lengths, and angles. These differ from previous models, which often used averaged properties. The data for the new models has been developed over several years and has required the analysis of information from hundreds of wells. These data have been input to simulation models to evaluate vertical and areal trends.
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Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach,
California, May 5-7, 1993.