Abstract: Reservoir Characterization and Simulation of a Multi-Pattern Pilot Area for Cymric Cyclic Steam Project

FONG, WILLIAM, Chevron USA Production Co., Bakersfield, CA; LARRY SKOW, Chevron USA Production Co., Bakersfield, CA; J. BAIR, Chevron USA Production Co, Bakersfield, CA; SCOTT JOHNSON, Chevron USA Production Co, Bakersfield, CA; JULIAN THORNE, Chevron Petroleum Technology Company, San Ramon, CA; PAT PERRI, Chevron USA Production Co., Bakersfield, CA

A successful cyclic steam project has been implemented in the Antelope Shale Formation of the Cymric field of California since 1997. This work utilized core and log data from 63 wells in the pilot area for reservoir characterization. Reservoir simulation model was developed for a four-pattern area within the pilot. The model was used to analyze and forecast field performance, and for aiding reservoir management decisions.

The reservoir characterization focused on the development of a detailed geological model around the pilot area. A neural network approach was used to predict high permeability streaks. Fracture heights were derived from temperature data at the cyclic steam producers and studies of fractures in analogous diatomite reservoirs. A 32 MM grid geostatistical model was scaled up to 93,000 grids for flow simulation of the four-pattern area in the center of the pilot. The simulation model was able to capture complex operational history and provided a good history match. The model was then used for subsequent recovery forecasts, 3D visualization, and sensitivities to various key uncertainties.

Results indicate that the current 5/8 acre spacing for cyclic steam injection is adequate. There is still significant potential for further infill to 5/16 acre for additional recovery. However, conversion to steam drive may be less feasible, due to potentially low injectivity and the presence of high-permeability streaks in the area. Continued small cycles, steam induced fractures, and infill drilling to less than 5/8 acre spacing can lead to a highly efficient recovery process in this low-permeability, heavy oil reservoir.

Results of this study can be used to design an efficient thermal recovery process in low-permeability, heavy oil reservoirs. This work demonstrates the importance of capturing reservoir heterogeneity, and the use of detailed multi-pattern models for modeling a cyclic steam project with steam-induced vertical fractures.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California