Schlumberger

Case Study: OR-13 Oxygen Scavenger Mitigates Severe Corrosion Risk in Seawater Injection System Offshore Denmark

Low-environmental-impact catalyzed scavenger rapidly reduces seawater injection system oxygen content, North Sea

Challenge: Mitigate severe oxygen corrosion while minimizing environmental impact in a seawater injection system of a production installation in the Danish sector of the North Sea.

Solution: Use OR-13 oxygen scavenger as fast, effective answer.

Result:

  • Successfully mitigated the impact of oxygen corrosion since the scavenger’s deployment with no reported issues.
  • Consistently demonstrated through routine analysis that the dissolved oxygen content was maintained within customer-defined acceptable limits.
  • Overcome and correct oxygen corrosion offshore Denmark

    A seawater injection system on an offshore North Sea platform situated in the Danish sector was at risk from severe oxygen corrosion. The offshore oil field consists of a number of platforms located on the Danish Continental Shelf, each with a number of satellites with production supported by waterflooding. The process is typical of a seawater injection system consisting of coarse and fine filtration preceding the mechanical de-aeration process, which culminates in the dosing of oxygen scavenger to ensure the achievement of very low levels of oxygen. The fluid chemistry is dynamic, with additional production chemicals being simultaneously deployed at various points along the system. The operator requested Schlumberger to provide an oxygen scavenger suitable for continual deployment that not only rapidly reduced the oxygen content but was also environmentally acceptable.

    Choose rapid, effective OR-13 oxygen scavenger

    Schlumberger selected, tested, and prequalified products that have a proven track record in similar cases. OR-13 oxygen scavenger was recommended based on high performance efficacy in systems that have short residence times and its inherent biodegradability coupled with use of a proprietary catalyst registered with OSPAR’s Preparations Used and Discharged Offshore Which Are Considered to Pose Little or No Risk to the Environment, ensuring minimized environmental impact. In addition to increasing the rate of oxygen consumption, the catalyst ensures a more complete reaction at lower dose rates, thereby avoiding potential solids deposition as a result of incomplete reaction. In this instance, OR-13 oxygen scavenger is injected into the de-aeration column at a dose rate appropriate to the level of dissolved oxygen in the fluids based on a typical dose rate of 30-ppm OR-13 oxygen scavenger per ppm of dissolved oxygen. Routine sampling and online oxygen content measurements enable further dose optimization.

    Successfully kept oxygen corrosion at bay

    At the time of writing, OR-13 oxygen scavenger has been successfully mitigating the impact of oxygen corrosion over numerous years and is still in current use. No issues associated with the deployment of the oxygen scavenger have been reported, and routine analysis has consistently demonstrated that the dissolved oxygen content was maintained within acceptable limits as stipulated by the operator for standard system operation.


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