SUSTAINABLE CHEMISTRY CONTROLS CORROSION AND WATER-QUALITY ISSUES SUBSEA

SFPEC1589A DEMONSTRATES IMPROVED CORROSION INHIBITION PERFORMANCE AND ENVIRONMENTAL PROFILE.

SITUATION

The operator of an offshore gas-condensate field in the UK sector of the North Sea managed corrosion in three high-temperature, high-pressure, high-shear subsea fields with a proven, umbilical-certified corrosion inhibitor (CI). The treatment program called for injecting CI downstream of the subsea well heads to protect system pipelines.

For a period of time, quality tests of produced water to be discharged overboard following separation found oil-inwater (OIW) concentrations exceeding 2,000 ppm, well beyond the 30 ppm allowed by the Department of Environment and Climate Change (DECC), which oversees environmental protection in the UK North Sea. Additionally, DECC had classified several chemical components of the incumbent CI for substitution warnings.

The operator needed new corrosioninhibition technology that could perform as well as or better than the incumbent CI, be formulated with active chemical components not targeted for substitution under environmental rules, and enable more effective operations by not contributing to the stability of emulsions in the production stream.

SOLUTION

Nalco Champion incorporated advanced testing protocols and the accumulated knowledge of technology centers in Europe, Asia-Pacific and North America to investigate the potential of developing chemistry to replace the incumbent CI.

We performance-tested candidate formulations for emulsification tendencies and stability under extreme temperature fluctuations. Chemistries that passed initial tests were subjected to high-level corrosion testing in extreme conditions, including low-shear and high-shear conditions and high pressures. Nalco Champion established the critical pitting temperature of each remaining candidate chemistry and evaluated each under simulated subsea conditions with the rigorous Nalco Champion SurFlo® Plus umbilical certification process.

Based on the comprehensive qualification data set compiled, Nalco Champion identified SFPEC1589A as the most promising candidate to replace the incumbent CI. After comparing the potential of SFPEC1589A and the incumbent CI for inhibiting localized corrosion in highshear conditions, results of emulsification testing showed the emulsion tendency of SFPEC1589A was significantly lower than that of the incumbent CI, as illustrated in Table 1.

table

Emulsion testing confirmed the low OIW properties exhibited by SFPEC1589A, a performance characteristic that would enable it to comply with the 30 ppm ceiling set by the DECC for oil contamination in wastewater discharged offshore. Additionally, DECC had approved SFPEC1589A for use in the UK North Sea with no componentsubstitution requirements.

RESULTS

In addition to demonstrating better corrosion-inhibiting performance, the comprehensive qualification data set compiled by Nalco Champion showed that SFPEC1589A also exhibited a significantly lower emulsification tendency, which reduced oil contamination of wastewater discharged overboard to less than 30 ppm, allowing the operator to comply with DECC quality requirements and avoid:

  • DECC fines for overboarding out-ofspecification wastewater.
  • Potential costs associated with storing wastewater on-board the host platform while awaiting pick-up by a support vessel.
  • Risk of upsetting the production system by reinjecting wastewater downhole.

SFPEC1589A also proved to be compatible with the incumbent chemistry, ensuring that SFPEC1589A could be introduced to the same storage tanks and umbilical or capillary lines without fear of subsea system upset.

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Localized corrosion is a prominent concern in the infrastructure of many subsea systems due to metallurgical differences of the pipe, heat-affected zones and weld material.

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TEST YOUR PPE

Personal protective equipment (PPE) is the last line of defense, including retractable lanyards. A diligent employee at the Ellwood City Plant tested the arrest mechanism and found it to be defective. The unit was replaced immediately.
Carrie Birckbichler-Smith
SH&E Supervisor

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