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Monitoring Oil Saturation Change with Carbon/Oxygen Logs in Complex Wellbore Environments in California, Nigeria, and Angola

T. Zalan1, D. Julander2, D. Belanger3, A. Badruzzaman4, and T. Badruzzaman5
1Chevron Overseas Petroleum Inc, Bakersfield, CA
2Chevron USA Production Co
3Chevron Overseas Petroleum Inc
4Chevron Petroleum Technology Co
5Pacific Consultants and Engineers

One of the primary limiting factors in the estimation of water saturation from Carbon/Oxygen (C/O) ratios is the level of accuracy in the understanding and characterization of the wellbore environment. C/O logs are often run in complex wellbores that are outside the normal range of conditions characterized by the service companies. This paper shows examples of C/O logs from Kern River (California), Angola, and Nigeria that have been recorded in complex wellbore environments, such as: (a) through tubing-casing annuli, (b) large wellbores, (c) through gravel packs, (d) oil-contaminated observation wells, and (e) gas columns. Such environments are not yet characterized by the service companies. The examples serve to document what can be achieved in less than ideal C/O logging conditions.

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