Determination and Prediction of Wax Deposition from Kuwaiti Crude Oils

Abstract

Abstract Crude oils produced from the formations are transported and processed at low temperatures where solid wax particles may precipitate. These solid particles cause additional pressure drop in production tubing, pipeline, and processing equipment and eventually cause plugging. Great saving in the cost of operating such equipment can be achieved from accurate prediction of wax appearance temperature (WAT) and the amount of wax formed at given conditions. This paper reports measurements of wax content by acetone precipitation techniques as well as measurements of wax appearance temperature (WAT) by viscosity measurements and differential scanning calorimetry (DSC) of eight different stock-tank Kuwaiti crudes. Viscosity measurements indicate that crude oils exhibit Newtonian behavior at temperature above WAT and Non-Newtonian elsewhere. Comparison of WAT measured by DSC and viscosity indicates that the viscosity method overestimates the WAT. Crude oil gravity measured, by digital density meter, and molecular weight, by vapor pressure osmometer, were used to characterize the plus fraction and predict WAT and amount of wax formed at given condition by the thermodynamic model. Comparison between predicted and measured results shows that measured Wax appearance temperature (WAT) by DSC compare very well with that predicted from the model for most crudes. However, Wax contents measured by modified UOP method 46-64 are not in good agreement with that predicted by the thermodynamic model.