Wax deposition during pipeline transportation of crude oil is one of the serious flow assurance problemsfaced in the petroleum industry (Deka et al., 2020b) and wax gelation phenomenon is an inherentcharacteristic of the wax deposition process and it must be investigated to understand the deposition process.Wax-gelation formation was simulated during flow of waxy oils by numerically simulating its gellingbehavior during transportation under different operating conditions by developing a computational fluiddynamics (CFD) model. The modelling technique and the obtained results from this work would help topredict the wax deposition and gel formation tendency in different waxy oils. Wax deposition phenomenonwas modelled for a model wax-oil mixture (representing a waxy oil). A numerical model was developedto predict the wax gelation with time and length of pipeline. It involves heat and mass transfer calculationsand molecular diffusion mechanism is considered as the primary mechanism for wax deposition, withthe calculations being performed for 5 days. The CFD model uses enthalpy porosity technique wherewax-oil gel is treated as the solid-liquid region with porosity equal to the liquid fraction. Fluid flow wasconsidered laminar with flow rates being 1-5 GPM and ambient temperature was maintained at 281.3 K.The developed numerical model predicts that the wax gelation increases with time initially and then sloweddown subsequently and less increment is observed upon 5 days of fluid flow. These results indicate the waxgelation is fast initially and slows down subsequently, showing strong dependence on time. Wall temperatureof wax-oil mixture and the gel deposit decreases from bulk fluid temperature (295.2 K) to the ambienttemperature (281.3 K). Increase in the temperature difference between wall and ambient temperature leadsto higher wax deposition and gelling formation. Wax gelation was observed to be function of time. The CFDmodel numerically-simulates the wax-oil gelling formation in terms of liquid fraction (gel formation), wherethe liquid fraction gets reduced up to 44.7 % upon crude oil flow in the pipeline, being highest at the centreand lowest at pipe-walls, indicating the possible gel formation regions on pipewall. The gel formation wasstrongly affected by the wall temperatures, duration and length. This work would be one of its kind to reportCFD-simulations of wax-oil gel formation in pipelines, where interdependency of fluid flow parameterswould be assessed. Therefore, in this work, an attempt was made to simulate the gelling behaviour of thewax crystals in pipeline using an enthalpy porosity technique which has been not been tested much before.
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