Active heating of thermally insulated flowlines

摘要

Hydrocarbon liquids are transported from a subsea welihead to an above-surface hydrocarbon processing facility along a pipe-in-pipe flowline. The flowline is a pipe placed coaxially within an outer carrier pipe and the annulus between the pipes is filled with thermally insulating material. The hydrocarbon liquids have their temperature maintained above solidification/precipitation temperature by heat from an active heating system. Hot liquid, preferably hot water, is passed along the annulus, either along a single pipe or multiple pipes installed in the insulation-filled annulus, or along an inner annulus formed by a water pipe added concentrically around the hydrocarbon-transporting inner pipe, inside the outer insulation-filled annulus. The water or other suitable liquid can be heated in a heater at or adjacent the subsea wellhead, or by a water heater in the above-surface hydrocarbon processing facility.