Paper Number
GN24                         My Program 

Session
Gels and Networks

Title
Understanding the complex rheology of waxy crude oils: Effects of composition, cooling, and shear

Presentation Date and Time
October 15, 2024 (Tuesday) 1:50

Track / Room
Track 1 / Waterloo 3

Authors (Click on name to view author profile)

  1. Ogunwale, Samuel (University of Michigan, Chemical Engineering)
  2. Mahir, Luqman (University of Michigan, Chemical Engineering)
  3. Shetty, Abhishek (Anton Paar, Rheology)
  4. Larson, Ronald (University of Michigan, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Samuel Ogunwale1, Luqman Mahir1, Abhishek Shetty2 and Ronald Larson1
1Chemical Engineering, University of Michigan, Ann Arbor, MI 48105; 2Rheology, Anton Paar, Ashland, VA 23005

Speaker / Presenter 
Ogunwale, Samuel

Keywords
experimental methods; gels; networks; non-Newtonian fluids

Text of Abstract
Waxy crude oils exhibit complex rheological behavior that poses significant challenges in their production, transportation, and processing. This study systematically investigates the influence of wax composition, cooling rate, and shear history on the gelation, yield stress development, and structural evolution of model wax-oil mixtures. By employing two complementary experimental protocols, the Temperature Arrest Measurement (TAM) and the Four-step process, we elucidate the intricate interplay between these critical factors and their impact on the flow properties of waxy oils. The Four-step process, which includes beneficiation, temperature ramp, shear rejuvenation, and shear rate sweep steps, reveals the significance of shear rejuvenation time in obtaining a true steady-state flow curve. Prolonged shear rejuvenation leads to the collapse of distinct flow curves, obtained at different maximum shear rates, into a single curve, challenging the previously reported shear history dependence. The cooling rate markedly affects the gelation process and the waxy oil microstructure development, with slower cooling rates resulting in prolonged shear and lower viscosities at the final temperature. The TAM protocol provides critical insights into the effects of imposed shear stress, cooling rate, and wax concentration on the gelation temperature and yield stress of waxy crude oils. Higher imposed shear stresses necessitate lower temperatures to arrest the flow, attributed to the degradation of the wax network structure. Slower cooling rates and higher wax concentrations lead to lower gelation temperatures due to increased shear-induced degradation and the need for more wax crystals to resist flow. This study contributes to a deeper understanding of the complex rheological behavior of waxy crude oils and the underlying mechanisms governing their flow properties. The findings lay the foundation for developing