This paper reports the results of using an improved impulse oxygen activation logging tool for water flood surveillance in the Kuparuk River Field, Alaska. The modified logging tool now enables the monitoring of water injection profiles in the "selective single" well completions over a wider range of injection rates with better vertical resolution when compared with an earlier impulse oxygen activation tool configuration.

The resolution and dynamic range of this service have been improved with a modification to the pulsed neutron tool. The modification increased the vertical resolution at high injection rates from 15-ft to 6-ft. Using a series of station measurements, it is possible to measure water velocities from less than 2 ft/min (0.01 m/s) to 300 ft/min (1.5 m/s). Knowing the cross sectional area of the casing/tubing annulus, water flow rates from 10 to 9500 BWPD are directly calculated.

These measurements have provided injection profiles to determine vertical conformance and the need for profile modification. Three case histories are discussed. 1.) The results of the pre- and post-logging programs are presented as well as the results of the successful profile modification. 2.) Detection of thin high permeability thief zones. 3.) Multiple water velocities measured in the same direction at same time to determine the injection profiles inside and outside of the tubing. This has all been possible with the successful modification of the WFL* tool to increase its vertical resolution. Impulse oxygen activation logging has become crucial to the continued surveillance of the secondary recovery project of the prolific C Sand in the Kuparuk River Field. Additionally, the information could be used to make an assessment of ultimate recovery, the need for infill drilling and enhanced recovery processes.

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