Experimental Study of the Cold Restart of a Pipeline Filled With a Gelled Waxy Oil

Experiments were conducted on the flow field start up behavior of a gelled waxy oil in a pipeline. A simulant fluid was used to mimic the low temperature rheology of crude oil. The break down of the gelled simulant fluid was studied during different startup conditions. It is shown that the “failure mode,” or manner and location in which the gelled simulant fluid breaks down, is closely related to both the temperature of the gel and the cooling time prior to pressurization. Flow visualizations indicate that for higher temperatures, and long cooling times, exists a weaker gel strength and failure occurs near the centerline of the pipe. Lower temperatures and long cooling times result in the breakdown of the gel at the pipe wall. Shorter cooling times result in a weak centerline gel strength, and results in gel failure near the centerline of the pipe. Pressure and temperature data were acquired at seven locations along the length of the test section, and these data were correlated to the velocity field, measured using Particle Image Velocimetry. Combined with rheology measurements, these data, allowed for shear stress estimates to be made. For the parameter ranges explored, the results exhibit three different failure modes, each associated with a different set of initial conditions. A critical temperature existed above which one failure mode was encountered and below which another failure mode was found. A third failure mode was associated with a cross-section that did not have a uniform radial temperature profile.