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Journal of Applied Sciences
  Year: 2014 | Volume: 14 | Issue: 11 | Page No.: 1114-1122
DOI: 10.3923/jas.2014.1114.1122
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Yield Stress Measurements of Waxy Crude Oil

Jaspreet Kaur and Azuraien Jaafar

Predicting the restart pressure for gelled waxy crude has always been a challenge due to the thixotropic nature of the crude apart from the thermal shrinkage and presence of gas voids within the gelled crude. Yield stress is the stress corresponding to the transition from elastic to plastic deformation, the value of shear stress above which the material flows. Existing method defines two yield stresses, one static and one dynamic. While static yield stress is more difficult to measure since most occur at very low stresses and that the measuring methods is still subjected to many debates whereas the dynamic yield stress is relatively easier to be obtained and requires linear extrapolation of viscosity data at high shear rates. There are many methods can be used to measure the yield stress which are the creep recovery test, stress ramp test, oscillatory test, vane technique and many more. In this study, the comparison will be done using all the mentioned methods and how a new method has been developed to accurately measure the yield stress for the waxy crude oil. The new proposed measurement for static yield stress was done with oscillatory testing and dynamic yield stress with steady state peak hold testing. All measurement was done under the rheometer with minimized wall slip effect for both statically and dynamically cooled sample. For the yield stress measurement, it also exhibited some interesting features of the waxy crude oil. The outcome of the study could then be used to fully understand the nature of the gelled crude.
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How to cite this article:

Jaspreet Kaur and Azuraien Jaafar, 2014. Yield Stress Measurements of Waxy Crude Oil. Journal of Applied Sciences, 14: 1114-1122.

DOI: 10.3923/jas.2014.1114.1122






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