Wax deposition in pipelines

Deposited wax increases the effective inner diameter of the pipeline resulting in an increased pressure drop. Unless the wax is removed, the pipeline may eventually plug up with wax. The developed program may be used to predict: whether wax depostion will take place; how fast the thickness of the wax layer will increase with time; the pressure drop resulting from wax deposition. The program is well suited for planning how often the wax has to be mechanically removed (pigging frequency). Two deposition mechanisms are considered, molecular diffusion and shear dispersion. By molecular diffusion wax molecules from the bulk phase diffuse towards the cooler wall and deposit on the wall. Shear dispersion is deposition of already precipitated solid wax particles. The primary elements of the projects have been: improved thermodynamic model for wax precipitation. This model has an enhanced description of the effect of pressure on wax precipitation; Wax deposition model. The developed model is fully compositional an can be used to predict wax deposition in pipelines transporting well streams with up to 4 phases (gas, oil, wax and water); viscosity model for oil with dispersed wax. Wax deposited in the oil phase may have a tremendous effect on the apparent viscosity of the oil. This results in an increased pressure drop in the pipeline. A model has been developed for the prediction of the viscosity of an oil with solid wax particles