Vacuum insulated tubing (VIT) can successfully solve or prevent many production problems caused by the transfer of heat from produced reservoir fluids into surrounding formations and casing annuli including paraffin (wax) deposition, hydrate plugging and annular pressure buildup in the outer casing strings.
VIT is constructed using two concentric tubing strings of different diameters, with the annulus between them sealed by welding. The thin layer of air between the tubulars is evacuated with a vacuum pump, thus creating an insulated jacket. With VIT, fluid temperature loss is approximately 10ºF (5.6Cº) over 5,000 linear ft (1524 meters), compared to a loss of 80ºF (44ºC) or more over the same length of conventional tubing.
By reducing the outward migration of heat, utillisation of VIT ensures:
- Delivery of steam to reservoir injection points at higher temperatures than would otherwise be possible during steam assisted operations. The increased heat transfer into the producing formation, reduces steam consumption and water usage. The result: more efficient lifting costs and reduced loads on the steam generation systems ensuring overall reduction in not only operational costs (energy and time), but also reduced impact to the environment whilst increasing operational safety.
- Mitigation of Annular Pressure Buildup (APB) by reducing heat transfer from the production flow to the fluids in the casing annuli.
- Paraffin or “wax” deposition and build up is prevented by ensuring the temperature of produced fluids doesn’t fall below the wax deposition (cloud point) temperature thereby avoiding or reducing costly intervention activities which usually consists of shutting down production and using mechanical or chemical means to remove buildup.
- Prevention of methane gas hydrates crystalision due to too low temperatures: VIT’s heat retention capability can greatly improve cold start-up/warm-up times and minimize hydrate crystallization formation risks which can plug the flow line or production string.
Environmental concerns are addressed with VIT preventing heat transfer from warm formation fluids to the surrounding permafrost in oil fields like Alaska’s North Slope. In addition to preventing environmental damage, potential structural failure of wells due to subsidence of the melted formations is also addressed.
VIT allows produced fluids to flow at higher temperatures thereby maintaining lower viscosity and increasing flow and enhancing profitability.