Increasing trend in the transportation of unprocessed reservoir fluid from assets located in remote locations and the drive towards maximising existing facilities and optimising production has encouraged many deepwater operators in the use of long subsea tiebacks. However, the main challenges associated with unprocessed multiphase fluid flow in long subsea pipelines relate to constantly changing patterns and the likelihood of the suspended particles to settle out of flow and deposit in the transfer pipeline causing partial or complete blockage. Flow pattern transition is therefore a critical factor that must be accounted for in any particle transport models. However, current particle transport models do not account for these critical factors; besides the experimental data on which these models were validated are limited. Therefore they are often unreliable when subjected to varying operating conditions. In this paper preliminary minimum transport velocity (MTV) models developed for rolling and suspended particles under different flow patterns are presented. The concept of particle velocity profile provided the basis on which the models were developed. Further work is planned to acquire large experimental data for the purpose of validating these proposed models. The problem has been largely attributed to insufficient flow velocity among other parameters required to keep the solids in suspension and prevent them from depositing in the pipe. Additional complexities are introduced because of different flow regimes that occur within the pipe flow depending on the gas and liquid flow rates. The development of minimum transport velocity models for suspension and rolling based on the concept of particle velocity profiles is a significant breakthrough in particle transport in multiphase flow. This has the potential to solve problems of pipe & equipment sizing, risk of sand deposition & bed formation, elimination of costs of sand unloading, downtime and generally improve sand management strategies.
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