Flow assurance challenges associated with waxy crude
oil precipitation
at low ambient conditions are significant concerns for oil industries
during production, transportation, and storage. Numerous methods have
been employed to mitigate wax deposition and gelation issues. Since
wax precipitation is temperature-sensitive, heating has emerged as
a promising method to enhance oil flowability. The present work intends
to examine the degelation behavior of waxy oil using rheometry, differential
scanning calorimetry, and microscopy techniques. In addition, a non-isothermal
flow restart simulation is performed using an in-house numerical simulator
consisting of a rheological model of sol–gel transition developed
in the current work. A numerical simulation of a preheated gelled
pipeline demonstrates the significance of the degelation temperature.
The effects of the wax concentration, initial gel temperature, and
aging period on the degelation temperature are examined. The observed
degelation temperature is higher than the gelation temperature, leading
to thermal hysteresis. The extent of thermal hysteresis reduces with
a decrease in the heating rate. The numerical simulation uses the
finite volume method with variables placed on a staggered grid. The
gel heated above and below the degelation temperature shows a significant
variation in axial velocity profiles. However, further heating does
not affect the velocity profiles. A shear banding type of effect is
observed in the axial velocity profile above the degelation temperature.
Heating the gelled oil to the degelation temperature instead of the
wax disappearance temperature saves excessive heating energy during
storage and transport operations.