Case studies: New concepts in CP systems for brownfield assets
by Jim Britton (2016)
As offshore infrastructure ages and the price of oil remains low, the corrosion industry is challenged to find better ways to maintain the integrity of subsea structures. In this context, better means more cost-effective; to develop the most cost-effective system we must approach the problem from the owner’s perspective and ask the right questions. How long does the system have to remain in operation? Are we willing to take on some maintenance work to show an initial cost reduction? Are we willing to consider a shorter life extension and repeat the process when required? Are we willing to change?
Deepwater has pioneered many new methods for offshore cathodic protection life extension over the years, and we have learned quite a few lessons. The following case histories demonstrate not only how different the solutions are, but that they share one thing in common: Each solution is the most appropriate and cost effective for the owner of the asset.
PROJECT CASE HISTORY NO. 1
STRUCTURE - The structure is a fixed steel drilling / production platform located in 160 meters of water in the northern North Sea [Fig. 1]. The platform was installed in 1980 and was fitted with sacrificial aluminum anodes. The platform is still viable and serves as a critical hub for major fields in the area. Based on this utility, the operator required a 20-year life extension. A survey showed large areas of the structure to be inadequately protected with readings in the range of (-) 0.680 V vs. Ag/AgCl sw. recorded on parts of the structure. It was determined that the large eight-legged structure required a retrofitted cathodic protection current capacity of 7500 Amperes.