Towards prediction – and prevention – of petroleum pipeline plugging

Simple fluids, such as water, can undergo abrupt transitions to solid as temperature is lowered. Complex fluid suspensions, however, tend to solidify in more complicated ways depending on flow conditions, which can often lead to severe problems: When blood solidifies into a clot, it can cause a stroke, for example. In the petroleum industry, a ubiquitous problem is pipeline plugging by waxy oils, especially undersea where temperatures are low enough to crystallize the waxes.

By measuring viscosity and stress as a function of time in shearing flow, the distribution of structural shear stress, mimicking the conditions in a pipeline, Ogunwale et al. characterized the viscosity buildup and the rates at which such waxes solidify under various temperatures and flow histories, which describe how prior flow influences current rheology.

“Simulating the gradual cooling of a wax-containing oil in a shear rheometer, we found the conditions needed to reach a steady state depend strongly on both cooling rate and shear rate imposed during cooling,” said author Ronald Larson.

Their study covered a wide range of cooling rates, shear rates, shear histories, and wax compositions. While under high shear rates and higher temperatures, for example, the researchers found a steady-state stress for wax-containing oils can be reached in a matter of minutes, while it takes up to 48 hours at lower shear rates and lower temperatures.

“The next steps are to apply machine learning and AI tools to convert these data into mathematical relationships between flow, temperature histories, wax compositions, stress, and rate of solidification,” said Larson. “This has the potential to turn the plugging of pipelines into a predictable, and therefore more avoidable, occurrence.”

Source: “Dependence of rheological behavior of waxy oils on wax composition and cooling and shear histories,” by Samuel A. Ogunwale, Khalid Mateen, Thierry Palermo, Abhishek Shetty, Luqman Mahir, Annie Fidel-Dufour, and Ronald G. Larson, Journal of Rheology (2025). The article can be accessed at https://doi.org/10.1122/8.0001006 .