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An experimental rheometric investigation is performed to assess the utility of various gelation point determination methodologies. Controlled shear stress and controlled shear rate methods are developed to investigate gelation processes in waxy oils. The nonoscillatory rheological method exhibits high reproducibility for model wax oils as well as for real crude oils. In addition, the nonoscillatory methods are in good agreement with standard oscillatory gel point determination methods. The effect of imposed shear stress, imposed shear rate, and cooling rate on gelation point is investigated with two types of model oils: 5 wt % macrocrystalline wax in Primol 352 and 5 wt % macrocrystalline wax in dodecane. In addition, the effect of wax content on gel temperature of macrocrystalline wax in dodecane is investigated. Moreover, the effect of additives (A3 and A4) on gelation point of a real crude oil UL-YS1 is investigated. Finally, the gelation temperatures of 5 wt % macrocrystalline wax in Primol 352, crude...

An experimental investigation of waxy oil gelation behavior is performed using the methods of rheometry, optical analysis, tensiometry, and microscopy. Thermal history, shear history, asphaltene content, and chemical additives influence the gelation process. Consequently, the final gel state is strongly correlated to the gelation conditions. Various model wax–oil systems are prepared, including 5 wt % microcrystalline wax or 5 wt % macrocrystalline wax in dodecane, as well as 5 wt % macrocrystalline wax in Primol 352. Real waxy crude oils UL-YS1 and Se-7-E06 are also investigated. A new yield stress model is developed on the basis of experimental results and a modified Eyring theory to provide gel strength predictions for petroleum transport pipelines. In the absence of shear during gelation, the yield stress can be correlated with the thermal history. However, for non-quiescent gelation conditions, the gel strength is also dependent upon the imposed shear history during the gelation process. The imposed ...

Gelation and breakage of model wax–oil systems is investigated using microscopy, densitometry, rheometry, and XRD. Various model waxy oils are prepared, including 1 to 20 wt % (w/w) macrocrystalline wax in dodecane, 1 to 20 wt % microcrystalline wax in dodecane, and 5 wt % macrocrystalline wax in Primol 352. The influence of shear history, thermal history, and fluid composition is ascertained. A novel gel breakage model is introduced which spans the entire mechanical response of wax gels from initial Hookean behavior at low strains to equilibrium slurry flow at the infinite strain limit. The local rheology model will benefit shut-in and restart processes of waxy crude pipelines via application of standard fluid mechanics relationships.

«Petroleum is a complex mixture of hydrocarbons which is located in the Earth's crust in liquid, gaseous, and solid forms. Natural gas, heavy viscous oil and bitumens are forms of petroleum». This definition provided by а British encyclopedia is somewhat limited. Current scientific knowledge affords a more correct description of petroleum as a system containing numerous hydrocarbon components with different chemical natures. Such a correct definition allows a variety of physical properties and states related to internal structuring.