Options for Through Casing Saturation Logging in Fresh Water Formations

By

H. Rough (Schlumberger) and P. Mock (ChevronTexaco)

Midway Sunset is the second largest oil field in North America, located in the San Joaquin Valley in California. This field began production in the early 1900’s; secondary recoveries began in the mid- 1970’s including steam, water, and some residual fire floods. Current recovery methods coupled with fresh water formations create a difficult environment for oil measurement and production. Standard through casing tools, like Thermal Decay Logging (TDT) is inadequate.

Solving for oil saturation through casing has been a technology sought after by service companies and producers for many years. Well logging companies have recently matured several methods of through-casing evaluation. These include SLB’s Reservoir Saturation Tool (RST) a nuclear device, and SLB’s Cased Hole Resisitivity Logging (CHFR) tool where direct measurement of resisitivity allows an estimate of oil saturation.

Production companies have used a variety of completion methods at MWSS including gravel-packed slotted liners and lately tight slotted liners. More recently, logging has identified oil within the cased portions of older wells. This complex environment creates a logging challenge for even the most innovative technologies. During this project, a 30’ zone containing by-passed oil was discovered in a cased section of a well using SLB’s CHFR tool. This zone was perforated and the entire well was cycled with 10,000 BBLS of steam. This well, which pre-treatment was producing 5–8 BOPD, is now producing at a much higher rate, due to the CHFR method of oil determination. Because of this success, ChevronTexaco has identified several candidates at MWSS for similar treatment.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.