Experience with Active Flow Assurance

Abstract

Following the drop of oil prices during 2015 we have seen an increased attention from operators on using new technology, in particular active heating technologies. This paper presents an update to experience from early implementation with lessons learned to recent technology development of what today is the only field proven electric heating technology for rigid flowlines per today - Direct Electric Heating (DEH). It also discusses Electric Heat Tracing as promising technology undergoing qualification – but the main focus is on DEH. DEH had its technology qualification carried out in the 90-ties and early 2000's while the more recent years has focused on achieving long distance tie backs, qualification for deep water projects but also design alteration opening for cost reduction. Increased number of operators: During the first 10 years, all projects were in operation in the North Sea whereas during the last 8 years other operators has started using the technology, as well as applications in harsher environment and deeper waters. Deep water: Following internal testing to gain more information on material data of steel and copper, combined with an update in analysis technique – previous over-conservatism in design process can be reduced such that a more accurate analysis can be carried out. Consequently, cable designs which previously only were applicable for depths down to less than 800m WD can now be used at 1500m WD. Long distance step-outs: Wet design XLPE insulation to higher electrical gradients has been now successfully qualified, allowing DEH to be applied on longer distance tie-backs than before Technology improvements A 3-year R&D on high frequency DEH gives both technical advantages for interference with other subsea equipment, reduced AC corrosion as smaller conductors which leads to a significant cost reduction. With the above technical improvements alone or combined, and a better DEH system than that was qualified in year 2000 is now available to the market.