Modelling of wax deposition for waxy crude oil by ANSYS fluent

Wax deposition is a major flow assurance issue arises during pipeline transportation and wax gelation phenomenon, a fundamental characteristic of this deposition process, necessitates detailed investigation to elucidate the underlying mechanisms. The modelling approach helps in understanding the phenomenon of wax deposition and help in deciding appropriate mitigation technique during pipeline transportation of crude oil. Current study however aims to utilize Analysis of Systems (ANSYS) fluent software to model wax deposition phenomena using field data. The crude oil utilized for the study contains 38% wax and has pour point of 36 °C. The fluid flow was 1 GPM and the inlet temperature was 333.15 K which decreases up to 298.15 K. A Computational Fluid Dynamics (CFD) model was created to predict the wax gelation as a function of time, temperature and pipeline length for Indian crude oil using field data. It includes heat and mass transfer calculations, and the molecular diffusion process is considered as the mechanism for wax deposition. The CFD model in this work uses enthalpy porosity method where waxy oil is treated as the solid-liquid region with a porosity which equal to the liquid fraction. Moreover, the efficacy of the chemical additive was also evaluated in terms of liquid fraction by modelling approach in crude oil during pipeline transportation to evaluate its effect during field implementation. The results indicate that the wax deposition process is time dependent as it subsequently decreases with time. Furthermore, the temperature gradient between wall temperature and bulk fluid temperature also has a significant impact on wax deposition. Increase in the temperature gradient between wall and ambient temperature leads to increase the wax deposition and gelling formation. The use of Nanohybrid polymer (NHP) as an additive significantly improves the flow properties by reducing the wax deposition and increases the liquid fraction up to 75%. The study of CFD to model the wax-gelling process, with the wax gelation being monitored by analysing the variations in the liquid fractions of the crude oil aims to offer a thorough understanding of wax deposition and gelation phenomena in waxy oils, thereby facilitating the design of pipelines for waxy oils with suitable interventions, particularly under subsea conditions.