A waxy crude oil which gels below a threshold temperature has been investigated under static and dynamic conditions, using a combination of rheological methods, optical microscopy, and DSC. Particular attention is given in this work to the influence of the mechanical history on gel strength and to describing the time-dependent rheological behavior. The gels display a strong dependence of the yield stress and moduli on the shear history, cooling rate, and stress loading rate. Of particular interest is the partial recovery of the gel structure after application of small stress or strain (much smaller than the critical values needed for flow onset) during cooling, which can be used to reduce the ultimate strength of the crude oil gel formed below the pour point. A second focus of this study is to further develop the physical interpretation of the mechanism by which wax crystallization produces gelation. Gelation of the waxy crude oil studied is suggested to be the result of the association between wax crysta...

Rheological behavior and structural interpretation of waxy crude oil gels.

Morphology of paraffin crystals in waxy crude oils cooled in quiescent conditions and under flow

Crude oils are intricate mixtures of hydrocarbon compounds; different physicochemical characterizations must be performed to get to know their complexity. A series of four typical Mexican Crude Oil...

Fractionation and characterization of mexican crude oils

Wax deposition from Middle East crudes

Crude oils: characterization of waxes precipitated on cooling by d.s.c. and thermomicroscopy

Differential scanning calorimetry was used to study was precipitation from a series of North Sea crude oils by measuring glass transition temperatures, wax precipitation and dissolution temperatures (wax appearance and disappearance, respectively), and was precipitation and dissolution enthalpies in the temperature range from +70 to −140 o C. With respect to physical characteristics, the oils ranged from very light paraffinic condensates to heavy waxy crudes including biodegraded and asphaltenic oils. On the basis of glass transition temperatures, the oils could be sorted into groups that corresponded to their physical descriptions, whereas a similar grouping according to the precipitation or dissolution temperatures did not correspond to the physical characteristics

A.B. Nielsen

Papers

Wax precipitation from North Sea crude oils. 3. Precipitation and dissolution of wax studied by differential scanning calorimetry