Case Study

Cathodic Protection Replacement

Project description

As part of a major North Sea oil field an eight-legged jacket structure was installed in 1981. The jacket was fitted with approximately 2800 sacrificial anodes which had a design life of 30 years. Heavy anode depletion was formally noted in subsea reports. To ensure structural integrity to end of field life a new protection system was required. 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;

  • Retrobuoy anode sleds, positioned around the 500m zone
  • Subsea DC power cables routed through J-tubes to the platform topsides
  • Bespoke subsea wireless CP monitoring clamps
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
Timing and Duration

Commenced November 2014 (Duration 11 months)

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