Wax precipitation from North Sea crude oils: 1. Crystallization and dissolution temperatures, and Newtonian and non-Newtonian flow properties

Abstract

Summary and Conclusions Nearly all the oils studied were found to benefit from Energy & Fuels, Vol. 5, No. 6, 1991 907 thermal pretreatment, Le., preconditioning at 80 C, in that the pour points and viscosities in the non-Newtonian temperature range (generally below 30 C) were lowered. The pour points were in some cases lowered by as much as 30-40 C. This reflects the action of inherent pour point depressants (asphaltenes, resins) present in the oils. The exceptions to this rule were the condensates, which hardly contain any inherent pour point depressants. The pour point of thermally pretreated oil (minimum pour point) was in most cases 40-60 C lower than the WPT. On average, about 4 wt % precipitated wax (pulsed NMR data) was present at the minimum pour point. At the non-Newtonian temperature limit about 1 wt % was found to be present. Isoalkanes were the most abundant hydrocarbon class in wax fdtered from one of the oils at 40,23, and 6 C. The ratio isoalkanes/ n-alkanes