Eventos Anais de eventos
COBEM 2019
25th International Congress of Mechanical Engineering
MODELLING OF WAX DEPOSITION AND REMOVAL BY ELECTRICAL HEATING IN SUB-SEA OIL PIPELINES
Submission Author:
Daniel Albuquerque , DF
Co-Authors:
Daniel Albuquerque, Taygoara Oliveira, Eugenio Fortaleza
Presenter: Daniel Albuquerque
doi://10.26678/ABCM.COBEM2019.COB2019-1972
Abstract
Wax deposition in oil production and transportation pipelines is one of the main flow assurance problems in the offshore petroleum industry. The flow of waxy crude oils through sub-sea pipelines surrounded by cold water causes some long-chain oil components to precipitate and deposit on the inner pipe wall. These deposits grow thicker over time, causing oil flow rate reduction, increased pumping power and several other costs associated with removal and prevention of wax deposits. In this article, the wax deposition rate is predicted through the calculation of a mass balance on the wax-oil interface after numerically solving the heat and mass transfer equations in the pipeline. Molecular diffusion is considered to be the only relevant deposition mechanism. The thickness is then updated and used to calculate the new pressure drop across the pipeline as well as the updated heat transfer coefficients. Electrical heating of the upstream oil is used to remove the wax deposit, which is assumed to change phase at a constant temperature. The purpose of this model is to be the basis of an optimization algorithm for minimizing the usage of overall electrical energy, which includes both pipe heating and oil pumping energies. It is known that pipe heating is not a definitive solution to the wax problem for very long lines due to the fact that the dissolved wax is reintroduced in the oil flow and may form a new deposit further ahead. However, this technique is a cost-effective way of keeping the flow rate at a desirable level while postponing the necessity of pigging, which is a considerably more expensive operation, since it requires a production halt.
Keywords
Wax deposition, Flow assurance, Optimization
