Mixture temperature prediction of waxy oil–water two-phase system flowing near wax appearance temperature

Abstract

Temperature sensitivity of waxy crude oils makes it difficult to study their flow behaviour in the presence of water especially near their wax appearance temperature (WAT). In this study a method was proposed and implemented to mitigate such difficulties which was applied in predicting mixture temperatures (Tm) of a typical Malaysian waxy crude oil and water flow in a horizontal pipe. To this end, two analytical models were derived firstly from calorimetry equation which based on developed two correlations for defining crude oil heat capacity actualized from the existed specific heat capacities of crude oils. The models were then applied for a set of experiments to reach the defined three predetermined Tm (26 °C, 28 °C and 30 °C). The comparison between the predicted mixture temperatures (Tm,1 and Tm,2) from the two models and the experimental results displayed acceptable absolute average errors (0.80%, 0.62%, 0.53% for model 1; 0.74%, 0.54%, 0.52% for model 2). Moreover, the average errors for both models are in the range of standard error limits (± 0.75%) according to ASTM E230. Conclusively, the proposed model showed the ease of obtaining mixture temperatures close to WAT as predetermined with accuracy of ± 0.5 °C approximately for over 84% of the examined cases. The method is seen as a practical reference point to further study the flow behaviour of waxy crudes in oil–water two-phase flow system near sensitive temperatures.