Thermal and mechanical considerations for design of insulated tubing

Of the several options for controlling temperature in a well vacuum-insulated tubing (VIT) has proven useful in a number of applications. Use of VIT, however, necessitates unique design considerations, from both a thermal and mechanical perspective. This paper describes the application of VIT for a particular purpose-to minimize temperature change, and associated annular fluid-expansion pressures, in a deepwater well design. The specific application, however, lends background to more general design considerations associated with VIT. Thermally, the importance of heat loss at the couplings to the overall design is discussed, using both numerical analysis and experimental results previously reported in the redesign of wells for the Marlin terision-leg platform (TLP). Mechanically, a detailed examination of the loads to which VIT may be subjected also uncovers special considerations.