Numerical study for removing wax deposition by thermal washing for the waxy crude oil gathering pipeline

Exploring the wax removal process by numerical simulation is beneficial for guiding field operations. In this paper, enthalpy-porosity and volume of fluid (VOF) methods were adopted to simulate the melting process of wax in the crude oil gathering pipeline. The melting patterns and liquid fraction of the wax were used to validate the mathematical model. The results show that the wax melts quickly before the liquid fraction reaches 80%, while the remaining 20% melts very slowly. Since the water with higher density sinks to the lower part of the pipeline, the wax in the lower part of the pipeline melts first, while the wax in the upper part of the pipeline melts slowly. The water temperature and flow rate disproportionately affect the melting process. Increasing the water temperature and flow rate can accelerate the melting process, but the effects on shortening the melting time of wax gradually decrease. Increasing the flow rate, the heat transfer rate and the melting rate are increasing progressively, the change of flow rate also affects the outlet temperature of the pipeline.