Case Study

Cathodic Protection Replacement

Project description

TAQA’s North Cormorant platform is an eight-legged steel jacket structure, installed in 1981 with approximately 2800 sacrificial anodes which had a design life of 30 years. Heavy anode depletion was formally noted in subsea reports since 2007. In 2014, the jacket structure was found to have potential readings of -659mV at depths below -133m, which is outwith recommended guideline limit of -800mV vs. Ag/AgCl reference electrode. To ensure structural integrity to end of field life a new protection system was required to improve the jacket CP. Studies concluded that retrofit sacrificial anodes would not provide the required repolarisation current and the required physical size was impractical therefore a bespoke impressed current system was selected, comprising;

  • Eight seabed Retrobuoy anode sleds, positioned around North Cormorant 500m zone
  • Eight subsea DC power cables routed through two J-tubes, to North Cormorant topsides
  • Twelve bespoke subsea wireless CP monitoring clamps, installed on the East and West faces of the North Cormorant platform.
Our Scope

PDi were engaged to provide engineering and project management support for the cathodic protection upgrade project consisting of the following elements:

  • In-house engineering support
  • Ad-hoc analysis support
  • Management of offshore installation contractors
  • Management of subsea power cable manufacturing process
  • Management of design, fabrication and installation of Retrobuoy anode sleds
  • Management of design, fabrication and installation of bespoke ROV installable subsea monitoring clamps
  • Participation in project risk Review and HIRA’s
  • Management of J-Tube Caisson Extension contractor and Topside fabrication contractor
  • ICCP cable spooling and termination site support
  • Retrobuoy coaster loadout support
  • Winch FAT support
  • Subsea Wireless Monitoring Clamp FAT support
  • DSV mobilisation support
  • Offshore engineering support and supervision for:
    • EddaFauna ROVSV preparatory workscope
    • Seven Osprey DSV ICCP installation workscope
    • EddaFauna ROVSV subsea clamp installation workscope
  • As-built documentation support

​TAQA Bratani


UKCS, Northern North Sea


November 2014 (11 months)

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