THE INFLUENCE OF THE THERMAL HISTORY ON THE MECHANICAL BEHAVIOR OF WAXY CRUDE OIL

Diogo Elias da Vinha Andrade¹; Suelen Cristina Ferreira Baggio¹; Guilherme Arnt Serro Balvedi¹; Admilson T. Franco¹; Cezar Otaviano Ribeiro Negrão¹

¹ UTFPR

doi:10.20906/CPS/COB-2015-1381

Resumo

Waxy crude oils are Newtonian fluids at high temperature. The oil pipelines employed during the production and transportation of these materials are in contact with the seafloor. In this environment the temperature can be as low as 4 °C. At low temperatures, the solubility of the wax in the oil decreases and the precipitation of waxy crystals takes place. Crystallization of wax results in a non-Newtonian fluid behavior. As a result, the viscosity of the crude oil increases and even gelation of the material is possible when the flow is interrupted. Rheometric tests are extensively executed to analyze the influence of several parameters on the mechanical properties of the waxy crude oil at low temperature. The literature has shown that the thermal and shear histories have great influence on the rheological behavior of crude oil below the crystallization temperature. Before the rheometric tests, the oil sample is usually heated above the wax appearance temperature to dissolve all the wax in the oil. Then the oil is cooled until the test temperature and the experiment is performed. In the current work, rheometric tests are carried out to analyze the influence of the pre-test temperature. It can be anticipated that even above the crystallization temperature, the initial cooling temperature of the test has a great influence on the elastic modulus, gelation temperature and yield stress of wax crude oil.

Palavras-chave: waxy crude oil; rheometry; thermal history; initial cooling temperature