Numerical prediction of wax deposition in oil–gas stratified pipe flow

Abstract

Wax deposition in oil–gas two-phase pipe flow can be a significant flow assurance problem. It becomes complicated when gas phase flow is involved. In this work, a numerical model is proposed for the wax deposition for oil–gas stratified smooth pipe flow. A unidirectional flow numerical model is used to calculate the non-isothermal hydrodynamics, heat and mass transfer. The wax deposit layer is assumed to be a growing porous layer, which caused by the diffusion of wax molecules through a porous medium. The numerical calculation performance is illustrated by the lab-scale flow experiment. The model could give the non-uniformly circumferential distribution of wax deposit on the inner pipe wall, i.e. a crescent shape, and the predicted deposit thickness is shown to increase with an increasing in superficial gas velocity and superficial oil velocity. The trends in the model predictions compare satisfactorily with those from lab-scale experimental results. In addition, it was found that the concave-down configuration of the oil–gas interface must be taken into accounted for the wax deposit. Unfortunately, this has not been taken into account in all previous studies.