Evaluation Techniques in the Monterey Formation

S. T. Grayson
Schlumberger Oilfield Svcs, Ventura, CA

The Monterey of offshore California, is a mixed lithology, Miocene age formation, which contains extensive intervals of fracturing, folding, and faulting. Significant quantities of oil have been produced from wells completed in these fractured intervals since the 1960s. Monterey evaluation techniques have evolved over time. Recent advances have been made in while drilling, open hole, and production logging evaluations. Resistivity dips and images acquired while drilling (RAB LWD tool), have enabled geologists to confidently revise and update the geologic model in real time. This allows well trajectory to be modified on the fly in order to maintain the desired landing position and exposure in the productive interval. Resistivity images acquired on wireline (FMI), have provided the ability to identify, orient, and quantify individual fractures in the Monterey. This data has been used for reserve calculations, perforation selection, stimulation design, and well planning. Testing of fractured intervals can now be performed with the straddle packer module of the MDT tool. Use of this tool allows identification of fracture fluid, formation pressure, fracture permeability, and skin damage. Reservoir fluid contacts and pressure depletion can be monitored with this technique. Production logging has evolved to seeing small, discrete oil entries that emanate from fractures and flow up the high side of deviated wells. Quantification of entries and flow rates has provided valuable reservoir information and enabled successful through-tubing water shutoff efforts. These techniques have yielded a better understanding of the Monterey. This has resulted in a more efficient and successful exploitation of the reservoir.

AAPG Search and Discovery Article #90904©2001 AAPG Pacific Section Meeting, Universal City, California