Comparison Between Computer Model Predictions and Survey Data of Interactions Between a FPSO and Subsea Cathodic Protection Systems

Deepwater Oil & Gas developments consist of many more components designed to extract, transport and store the oil when compared with developments in shallower waters. Designing the cathodic protection [CP] systems to protect the individual components is problematic without an appreciation as to how CP systems fitted to the various components will interact with one another once the entire asset is commissioned.

For a deep-water project, a computer modeling study was commissioned to provide information on the performance of the CP systems protecting each of the subsea structures and the interaction currents flowing between them. The principal aim was to ensure that the impressed current CP (ICCP) system on the hull of the FPSO would be operated in such a manner as to reduce interaction with the sub sea sacrificial anode CP systems to the minimum possible throughout the operating life of the field and to develop an understanding of the probable behavior of CP systems on the key components (FPSO, Oil offloading lines etc.).
Data is available from surveys and the paper will compare the model predictions with the measured data. The paper will describe the strategy and rationale behind the modeling studies and some of the major lessons learned.