Electric Heating of Pipelines and Large Export Flowlines > 30" and more than 100 km

Abstract

Abstract Direct electric heating (DEH) of long flowlines and large export pipelinesprovides many advantages compared to alternative methods. DEH has been appliedactively in the past 10 years to prevent hydrate formation and is now breakingnew ground that was not previously considered feasible. By using qualifiedtechnology and existing design models, longer and larger pipelines can beheated intermittently or continuously. Electric heating of pipelines is attractive for long step outs greater than 100km, as DEH running costs are considerably reduced compared to the use ofchemicals. The technology is unique and commercially and technicallyattractive. It allows for the use of DEH for both infield flowlines and exportpipelines of 30" and above. An increased number of DEH systems have beenevaluated for oil and gas field project developments on continental shelvesaround the world, and the extension of this new technology will give higherflexibility in operation of the fields during planned or unplanned shut downs. Material aging and other failure mechanisms caused by high temperatures andwater pressure are also of great importance. Accuracy in design and analysis aswell as industry experience are important in solving project specific hydrateor wax issues in long DEH systems. The system is easy to install and operate and has low CAPEX and OPEX costs. Anew cable design and installation method has improved the robustness of theoverall system and makes the system more compatible with large and heavy pipeson the seabed. New condition monitoring also secures optimal heat input andimproves service-life. Complete heating systems for large export pipelines, with power supply fromshore, are available within the industry. Abbreviations DEH - direct electrical heating. DEHC - direct electrical heating cable (cable piggybacked to thepipeline). DEHS - direct electrical heating system. CWC - concrete weight coating. CTZ - current transfer zone.