Integrated Flow Assurance and Corrosion Assessment of a Subsea Pipeline

Background

As part of Atteris’ life extension assessment of a carbon steel export pipeline, an internal corrosion assessment was required. The assessment required accurate operating data; however the nearest process instrumentation was 15 km upstream of the carbon steel pipeline section.  Historical flow assurance modelling was required to infer the carbon steel pipeline’s top of line condensation rates and general operating conditions in order to assess its corrosion history.

Work Performed by Atteris

Atteris created an OLGA steady state model of the pipeline system and ran a number of parametric cases to cover all possible combinations of flow rate, ambient temperatures, pipeline burial ranges and other variables. Atteris then used this parametric data to estimate all combinations of possible top of line condensation rates (and operating conditions) on each of the 1500 days of operation. The historical data was then grouped and analysed by Atteris’ corrosion consultant. The work concluded that historical corrosion rates were within design limits.

Benefit

Atteris’ integrated flow assurance and corrosion engineering justified a deferral of the next in-line pig inspection using a risk-based approach, thus deferring the high cost associated with a subsea pig launching operation.