Mathematical modelling of wax-deposition in pipeline systems
Research output: Thesis › Master's Thesis › Research
Oil and gas transport is today a vital part of the industry. As oil is transported through a pipeline system, a cooling process occurs due to heat loss to the surrounding. Therefore wax may precipitate as a solid phase when the bulk temperature drops below the Wax Appearance Temperature (WAT) and wax can deposit on the pipe wall. These wax precipitations can cause severe operational problems like reduced flow area or complete blockage of the pipeline system, when the wax deposition process stays untreated. The goal of this work is to investigate modelling concepts for wax deposition in pipeline systems - which in detail means the review and evaluation of available wax deposition models and mechanisms and to give an overview of available software packages for simulating and predicting wax deposition phenomena. To get reliable results of wax deposition simulations, it is necessary to evaluate the simulation results against experimental data. In general it is difficult to do experiments in real scale pipelines, therefore the solution is to perform small or medium scale experiments. These experiments have to be performed in the laboratory. In so called flow loops, the behavior of oil and oil products in the production system can be examined with a flowing medium. This thesis also gives an overview on existing experimental rigs for studying wax deposition phenomena. A wax deposition experimental study compared to simulation results using most popular OLGA software simulator is also investigated in this thesis. The objectives of this study were to investigate the characteristics of a crude oil from offshore Brazil and utilize the measured data to compare with simulation results. Generally it can be seen that wax layer thickness increases with decreasing oil temperature for constant flow rate and oil temperature and the experimental flowing coolant (glycol) respectively and that there is the trend of the simulation software to under predict the amount of precipitated wax. As an outcome of this thesis further work should concentrate on the verification and testing of different software packages for several conditions and oils to better understand of the behavior of wax deposition in pipeline systems.