Project Review
Deepwater retrofits cathodic protection for the in-field flowlines on the Apache Forties field in the North Sea

Retro Clamp

Overview

In October 2007, Deepwater Corrosion Services in conjunction with Alliance partners Hockway Ltd. performed the first phase of a complete cathodic protection retrofit for Apache's Forties field, in the North Sea. Assets to be protected by "phase 1" consisted of:

• in-field pipelines, linking the 4 original Forties platforms (Alpha, Bravo, Charlie, and Delta)

The retrofit cathodic protection (CP) system consisted of:

• 12 RetroPods (Aluminum sacrificial anode 'pods')
• 7 RetroSleds (Aluminum sacrificial anode sleds)
• 38 RetroClamps for electrical attachment.

Installation

The Apache Forties Field is one of the oldest fields in the UK sector of the North Sea, seeing first production in 1975. There are 5 platforms making up the field, Forties Alpha, Bravo, Charlie, and Delta which were installed in the 1970’s, and Echo which was installed in the 1980’s. The bracelet anodes on the in field pipelines linking the four original Forties platforms were heavily depleted and required a cathodic protection system retrofit in order to maintain adequate levels of protection for the duration of the field life extension.

Hockway were nominated by Apache to provide a solution, and it was determined that the most cost effective retrofit would be by using the RetroSled, RetroPod and RetroClamp products manufactured by Deepwater. A detailed design was performed in order to calculate the optimum number of sleds and the correct sled spacing, and suitable subsea locations were selected for equipment installation to minimise the installation time.

Installation was performed in October 2007 under the supervision of Hockway and Deepwater engineers using an ROV support vessel, and successfully completed on time and on budget. Phase 2 of the project, which involves a complete retrofit impressed current cathodic protection system for each of the four (4) original structures using the RetroBuoy system, is scheduled for installation in Q3/Q4 of 2010.

Image Gallery

Apahce forties field in the North Sea

On of the forties field, platforms.

A RetroPod being loaded onto the vessel

A RetroPod being loaded onto the vessel.

RetroPods with RetroClamps attached on the deck of the vessel

RetroPods with RetroClamps attached on the deck of the vessel.

A view of the RetroClamp on one of the Sleds, with RetroReader attached. The RetroReader allows for visual confirmation of electrical contact with the pipeline during installation

A view of the RetroClamp on one of the Sleds, with RetroReader attached. The RetroReader allows for visual confirmation of electrical contact with the pipeline during installation.

A RetroSled being loaded onto the vessel

A RetroSled being loaded onto the vessel.

As-left survey of RetroPod and RetroClamp connected to flowline

Assembly of the {Pods and Sleds was completed in Aberdeen.

RetroSleds with RetroClamps attached on the vessel

RetroSleds with RetroClamps attached on the vessel.