Arnold / Oyster fields
Anode retrofit for two deep-water GOM subsea field developments
Deepwater RetroClamp™ was designed for rapid installation by ROV on pipelines.
Deepwater Corrosion Services performed anode retrofits on Marathon's "Arnold" and "Oyster" fields in the Gulf of Mexico. These two subsea development systems, located in water depths ranging from 775 to 1,750 feet, were retrofitted in just over 73 hours. Assets to be protected included:
• 4 flowlines, ranging in length from 3 to 9 miles each
• 4 well trees
• 2 flowline manifolds
• 2 umbilical termination units
The cathodic protection (CP) system consisted of:
• 19 RetroPods™ (Aluminum sacrificial anode sleds)
• Various standard and customized RetroClamps™ for electrical attachment.
Installation time: 3 days
The installation was accomplished utilizing a DP-equipped ROV support vessel equipped with two ROVs. An ROV essentially watches the RetroPod™ craned down to the seabed adjacent to the asset and sets the RetroClamp™ onto the target member or pipeline. Electrical continuity and CP measurements were monitored using Deepwater’s Polatrak® Deep-C Meter™ and ROV II™ probe.
The CP design was optimized in a manner that minimized the number of installation sites, but allowed for maximum flexibility with anode array placement. This design feature enabled the installation team to quickly alter the game plan when they encountered a major escarpment at one lay-down site.
The innovative RetroClamp™ system allows the anode array to be clamped and electrically connected to a member of any shape or size, completing the circuit necessary for the cathodic protection system to begin polarizing the structure or pipeline. The RetroClamp™ can be installed by diver or ROV (ROVs in this case).
Gallery
TARGET
The flowline as viewed by the ROV.
ROV installed
The ROV disconnecting the crane rigging from RetroPod.
Tubular Retroclamp
A Retroclamp engaging the round member of a well tree.
Flange Retroclamp
Two Retroclamps engaging the member of a well tree
Ballast
The Retropod has a concrete mattress in the base to provide ballast.
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