Name: Gabriel Gomes Vargas
Type: MSc dissertation
Publication date: 26/05/2017

Namesort descending Role
Edson Jose Soares Advisor *

Examining board:

Namesort descending Role
Edson Jose Soares Advisor *
Fabio de Assis Ressel Pereira External Examiner *
Flavio Barboza Campos External Examiner *
Roney Leon Thompson Co advisor *

Summary: Non-Newtonian fluids formed by dispersions, such as emulsions, solutions and gels, may exhibit viscoelastic, viscoplastic and thixotropic characteristics. When a waxy crude oil is subjected to low temperatures, its paraffin crystals precipitated, giving rise to a resistant structure. The understanding of this behavior at this critical condition is essential to analyze the restart of production in oil wells and pipelines after a production shutdown. The dimensioning of equipment used in the starting of these systems depends fundamentally on the yield stress of the oil in production. The dependence of the rheological characteristics of petroleum with the history of shear and temperature makes rheological evaluations complex, sometimes imprecise and with low repeatability. In this work the analyzes were conducted in a commercial type rheometer (Haake Mars III), using plate-plate geometry. Evidence indicates that the initial oil preheating temperatureisanimportantvariableintherheologicalbehaviorofthefluid. Theresults indicate that the initial increase in temperature causes a severe increase in yield stress upto 80◦C, abovethistemperaturethereisadramaticreversalintheyieldstressinthe two oils studied. It is also shown the variation of the yield stress with the change of the cooling rate that the oil is exposed and an analysis of the evaporation and loss of volatiles. In the complex study of emulsions, droplet size distribution measurements and morphological studies were performed. Important considerations are discussed here with respect to yield stress in low water cut emulsions and high water cut emulsions. Finally, a model is presented for checking the rheological parameters.
Keywords: Yield stress, waxy crude oil, Emulsion.

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