The Kuparuk River field, located on the North Slope of Alaska, is one of the United States' largest oil fields, producing approximately 300,000 BOPD. Initial development is on 160-acre well spacing with some 350 production and 270 injection wells. Production occurs from two horizons within the Kuparuk sandstone, referred to as the A and C sands. This situation requires the use of "selective single" completions that isolate the prolific C sands behind production tubing to enable fracture stimulation of the lower A sand and separate waterflooding of the two zones. The field has been under waterflood since 1983 and has experienced rapid buildup in water cut in C sand wells. During the past year, oxygen activation logging has been successfully applied to both injection and production wells to identify thief zones behind the production tubing and to provide important information to better manage the waterflood program.
A new method of using oxygen activation, the Water Flow Log (WFL*) service, provides the capability to trace water flow over a wide range of flow rates. The method is particularly well suited to measuring water flow in the tubing-casing annulus. Using a series of station measurements, it has been possible to measure water velocities up to 200 ft/min (1 m/s) at flow rates up to 4000 BWPD. Measurements have provided injection profiles to determine vertical conformance of the injection process. Similarly, water production profiles behind tubing have been recorded in several wells. In favorable cases, it has been possible to trace two parallel flowing water streams moving in the same direction and separated by production tubing.
Oxygen activation measurements are providing critical data for waterflood performance evaluation, assessment of ultimate recovery, and evaluation of the potential for infill drilling and enhanced recovery processes in the field. An operational benefit is that the need for radioactive tracer materials has been eliminated.
* Mark of Schlumberger