Production from fields developed in deeper and colder watersrequires that the hydrocarbons brought to the surface be at thehighest possible temperature to eliminate asphaltenes,paraffins and hydrates from blocking a production line. Goodinsulation allows a less viscous fluid to be produced at higherrates, extend shut-in period and reduce stress during expansionand contraction of pipes. Ideally, the annular space betweenthe riser and production line should be isolated with a special,low thermal conductivity fluid. Further, the insulation fluidmust be environmentally acceptable to mitigate the effects ofany spills or other unexpected events.The recent development of a lightweight hybrid riser for adeepwater completion in North Sea required a thermalinsulation fluid that was both cost effective andenvironmentally acceptable.This paper describes a unique joint project to develop alightweight riser and insulating fluid. The developmentincluded the building of a special test facility, which featured a20-m long (60 ft) full size aluminum riser with electricallyheated production pipe, which was filled with insulation fluid.The test piece was immersed into the sea for severalmonths exposure.The authors will detail several formulations, both mineraloil and water-base fluids including simple techniques tomeasure thermal conductivity, diffusivity and heat capacity.These data are compared to a specially developed computermodel and field data from long-term exposure test. Otherapplications of the thermal fluid is drilling through permafrostand insulating transportation lines.
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