There are many circumstances that lead to shutting down of oil pipelines for operational or emergency reasons in locations with ambient temperatures below the wax appearance temperature.Under these static conditions, paraffinic waxes in crude oils start to precipitate and form gels. Restarting the gelled pipeline, and eventually clearing the gel, requires the application of a pressure upstream of the gel that gives rise to a shear stress that exceeds the gel yield stress value.Pressure profile measurements and particle imaging velocimetry (PIV) experiments were performed both during gelation and after a sudden application of the restart pressure on a transparent pipeline containing a model waxy oil with measured rheological properties.
