Onset Crystallization Temperature and Deposit Amount for Waxy Crudes: Experimental Determination and Thermodynamic Modelling

Abstract

Abstract Paraffinic crude oils are often transported at conditions where heavy hydrocarbons contained in the oil may precipitate as a solid waxy material. This precipitation may plug the processing equipment. In the design of oil production facilities, it is therefore essential to be able to predict the conditions where wax crystallization may take place and the amounts of wax which may form. Several models have been proposed in the literature for the prediction of wax precipitation from natural crude oils. But they generally overestimate considerably the amount of wax precipitation below the wax appearance temperature (WAT). The objective of this study has been to develop a reliable compositional thermodynamic model to compute wax appearance temperature as well as the amount and the composition of waxy deposits as a function of temperature and to verify the proposed model with experimental results. This paper will describe the thermodynamic model and the complementary laboratory test methods. The agreement between the measured and predicted values for two crudes of different production areas is good.