This paper investigates the frequent tubing failure tendencies of standalone water injection systems with dual completions. The paper also recommends remedial solutions to mitigate tubing failures based on a rigorous evaluation. Standalone well designs include completing the same well in two water zones; a shallow producing zone and a deep injecting zone. The produced water flows naturally to the surface through the tubing casing annulus (TCA). A surface pump injects the produced water into the deeper formation through the tubing. Standalone dual completions present an attractive and cost-effective option of the Field-A water injector's well design, especially in populated areas inaccessible by pipelines.

The shallow water producing zone is known to be corrosive. The produced water has dissolved carbon dioxide, traces of hydrogen sulfide, and traces of oxygen. The standalone dual completion well design includes the installation of strapped stainless steel hydraulic control lines outside the tubing to allow pumping chemical corrosion inhibition treatment into the shallow producing zone.

The scope of this work assesses known attributes to tubing failures of standalone water wells. These attributes include galvanic corrosion and erosional corrosion due to fluid jetting effect. Methods of evaluation include collective inputs from the following:

  1. Chemical inhibition residual concentration analysis.

  2. Oxygen, iron, and sulfate reducing bactria (SRB) counts.

  3. Corrosion rate of coupons samples.

  4. Data from ultrasonic logs.

With availability of the above data, the corrosion attack mechanism was discerned. Also, tubing mean failure times were quantified using recorded leaks in several wells with varying status of operation over an extended period of evaluation. Insightful trends were generated during the monitoring period. The evaluated tubing types are carbon steel, corrosion resistant alloy, and glass reinforced epoxy wrapped tubing.

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