Analysis of Multiphase Production through Hilly Terrian Pipelines in Matzen Field—Austria by CFD

Abstract

Abstract Oilfield production pipelines follow normal hilly terrain variations including horizontal, uphill and downhill sections. Therefore, in the same pipeline it is possible to find several types of flow regimes at the same time at different position along the pipeline. Most of the possible flow regimes are not dangerous except slug flow. The slug flow is the most problematic flow regime since this may pose serious problems to the designer and operator of multiphase flow lines and production facilities. In this work, simulation of a full scale field pipeline is presented using Computational Fluid Dynamics (CFD) and the Volume of Fluid (VOF) method as a surface tracking model. The aim of the study was to investigate the type of flow regimes existing in Ma-VI pipeline system of Matzen field in Austria. A comparative study for different pipeline diameters has been performed and finds an optimum pipe diameter. The transient flow behaviour occurring in a pipeline with two different diameters has been simulated. Since the pipeline under consideration is nearly 2 Km long, the corresponding computational models would involve grid cells with very large aspect ratios which invariably would lead to solution instabilities in the CFD analysis. So, the pipeline system was sub-divided into different sections, and each section was investigated separately. Transient boundary conditions have been prescribed and the respective flow pattern, liquid-gas volume fraction and pressure drop have been estimated. The results show that the liquid slugs do not maintain a constant length along each section and the dissipation of slugging in up-hill sections mainly depends on the length, the angle and the diameter of the next downhill section. Various slug characteristics such as slug length, slug frequency, slug velocity and pressure drop have been studied and the computed liquid hold-up has been compared with eight correlations from literature. The ultimate aim of this work was to gain a deeper understanding of multiphase flow phenomena in pipeline systems and to develop guidelines to improve the design of pipelines and separation facilities.