ABSTRACT

New continuous oxygen activation logging technology is being used to monitor injection profiles in several carbonate reservoirs in the Middle East, where dual string completions are employed to control relative injection into intervals of markedly different permeability. In dual string completions, where short string water injection is conveyed via the tubing-casing annulus, oxygen activation logs often provide the only method for monitoring injection performance and for evaluating add and polymer treatments used to modify injection profiles. Accurate measurement of water flow in the annulus leads to a better understanding of hydraulic properties of the reservoir and improved design of water injection programs. Oxygen activation logging is also being applied to monitor water entry and rates in producing wells. Recent literature has described the latest improvements in logging instrumentation and interpretation methods allowing continuous oxygen activation logging for diagnosis of complex water flow conditionst5"6~. This paper focuses on recent experience in the Middle East with applications to a number of challenging monitoring problems uniquely associated with monitoring the short string injection or production in dual string completions, including:Determination of short string injection profiles for multiple sets of perforations Delineation of injection into sublayers of a reservoir within a single set of perforations Monitoring injection profiles during multi-rate injection tests Identification of fractured intervals and effects on injection profiles Monitoring the effectiveness of polymer treatments for water shut-off Mechanical integrity testing and location of channeling or tubing leaks Determination of water entry points and measurement of water rates in producing wells Recent examples with logs and histories are presented highlighting many of these applications. In one particular example, a comparison of continuous oxygen activation logs run in the dual completion and conventional spinner flowmeters run in casing prior to the dual completion illustrates the viability and accuracy of the method.

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