ZALAN, THOMAS A., Chevron USA Production Co., Bakersfield, CA; A. COLBERT REISZ, Chevron Petroleum Technology Co., La Habra, CA; RICK C. CAPRIO, Chevron USA Production Co., Bakersfield, CA; and WILLIAM S. FONG, Chevron Petroleum Technology Co., La Habra, CA

Abstract: A Comprehensive Three Phase Reservoir Characterization in the BeIridge Diatomite in Lost Hills Field, California: Unique Log Calibration, Mineral Modeling in Complex Lithology, and Permeability Transform Development

A full field reservoir characterization study was completed in the Lost Hills field, Kern County, California. This characterization was conducted in the Belridge Diatomite, the most prolific member of the Upper Miocene to Lower Pliocene Monterey Formation, to allow for the construction of more accurate and reliable reservoir models. These models may then be used to create value and optimize field development, improve volumetric calculations and reserve estimates, and conduct simulation studies and sensitivity runs which will allow us to evaluate different development strategies and potentially add reserves.

Log calibration was done with respect to developed geologic trend surfaces. The trend surfaces were created based on the average values of gamma ray, neutron, and bulk density logs in a calibration shale just above an areally continuous marker.

A log-based mineral model was developed, calibrated to bulk foot core mineralogy, and estimates of log-based porosity and saturation were compared with available core measurements. The log-based mineralogy and porosity were found to be consistent between traditional geologic markers across the field and across the opal-A/opal-CT transition. Also, an internally consistent methodology to estimate gas saturation was developed, which is expected to critically influence Lost Hills waterflood sweep efficiency.

Finally, a field-wide permeability relationship was developed using the multivariate transform method. Predicted permeability based on vertical subsea depth, bulk density, and resisitivity correlates to actual core air perms with a correlation coefficient r=0.84, and closely fits the one-to-one line.

AAPG Search and Discovery Article #90920©1999 AAPG Pacific Section Meeting, Monterey, California