Wax gel formation during the planned and the emergency shutdown became one of the important research topics in the flow assurance. Wax appearance temperature (WAT) and pour point (PP) are oil characteristics to predict the wax plugging. Measurement and examination of WAT and PP have been well studied using various techniques. WAT and PP have been critical properties in evaluating the flow of crude oils in colder environs. However the temperature difference (DT) between WAT and PP has not been established in detail. It is the aim of this paper to investigate the differences in the two measurements for different model oil systems to gain an understanding of the mechanisms governing the transition from WAT to PP in a waxy oil. A series of model oils with known amounts of well-characterized paraffinic wax composition were used. Model oils were prepared by mixing mineral oil and kerosene with different amount of waxes. The measurements of WAT and PP were performed using DSC, FT-IR, NIR, rheometer and ASTM methods. As the WAT and PP are dependent on wax amount and wax quality, this study examined the WAT and PP by comparing model oils with different wax composition as well as different wax amount. DT was observed to decrease with increasing the wax amount in model oils. Model oil with higher molecular weight of wax had higher values of DT. This indicates the mechanism differences in gel formation of waxes. In addition yield stresses were measured with rheometer using a vane method. Yield stresses were measured at different temperatures below PP for different model oils. Constant cooling rate and consistent holding time were employed for the yield stress measurements. It was shown that the yield stress is strongly dependent on the wax amount and wax composition. Vane method has a number of critical design variables, such as size of the enclosing chamber, temperature gradients in the chamber and cooling methods used. Yield stress values were observed to increase with decreasing measuring temperature in the examination range. Increase in yield stress values with decreasing temperature was greater for higher amount of wax in model oil indicating the gel strength is dependent upon the wax amount in the model oil.

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