Life Extension of Offshore Field in the Santa Barbara Channel 3: Subsea CP Retrofit of 7 Pipelines with Small ROV Vessel Enabled by Hot Stab Anode String Assemblies

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The Santa Ynez Unit (SYU) consists of three offshore platforms and an onshore oil and natural gas processing facility in Goleta, California. The platforms are located between five to nine miles offshore in federal waters. The construction of SYU began in 1976 in the Santa Barbara County in California with the platform Hondo (HO) which, started operations in 1981 to supply the domestic California market.

Product Number: 51323-19414-SG

Author: Omar Rosas-Camacho, Sami Abu-Zahra, Mathew L. Taylor

Publication Date: 2023

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Sacrificial anode cathodic protection (SACP) is used to prevent corrosion of submarine pipelines. Life extension of pipelines may require a CP anode retrofit and increased monitoring frequency. Electromechanical clamps or friction stud welding are often used to retrofit local anodes or semi-remote anode sleds. The spacing of retrofit anodes must be appropriately chosen to minimize installation costs while ensuring full protection of the pipeline at all points. CP test stations should be located midway between sleds, representing the worst-case potentials of the pipeline and accessible despite concrete weight coat or excavation.

In the current work, the retrofit of 7 pipelines with diameters ranging from 30.5 to 50 cm and lengths from 5.25 to 18 km was carried out using assemblies of anode strings attached to the pipelines via Hot Stab subsea clamps. A one-dimensional potential attenuation model was used to optimize the retrofit and CP-test station locations along with the anode geometry. The Hot Stab technology enabled anode installation by a small ROV and lifting equipment and simplifies future retrofits by eliminating the need for a new clamp. CP-test stations improve the value of CP survey by allowing faster traversal of the pipeline between stations and improving reliability and repeatability.