In this paper we have compared the OLGA HD stratified flow model against transient ramp-up and pseudo transient experiments from a Statoil funded experimental campaign performed at the SINTEF Multiphase Flow Laboratory. The experiments were designed to specifically target the transition point from low to high liquid holdup; the accumulation point. We have explained how the removal of the liquid, when the gas flow is increased to inside the multiple holdup solution region, can be described by a steady state fully developed flow approximation. OLGA HD showed excellent predictions compared to the accumulation point experiments. We have also compared the time needed to remove the liquid for a fully transient simulation of experiments with ramp-up into the multiple holdup solution region. A retuned version of OLGA HD, presented in , performed well also on the experiments where OLGA 2014.1 HD overpredicted the time needed to remove the liquid.
Multiphase flow simulations of gas-condensate pipeline transport are a challenging task. Important properties are the pressure drop for high rates and liquid accumulation at low rates; factors contributing to determining the operational envelope of the field. However, not only the liquid content and pressure drop at steady operating conditions are important but also behaviour during transient operations like rate changes and outlet pressure changes. The arrival time and the rate of the liquid after ramp-up may be critical factors when designing liquid receiving facilities and operational guidelines.
The work described in this paper originates from a project funded by Statoil where the uncertainty of OLGA for a gas-condensate field offshore Tanzania has been evaluated. The Tanzania project is described in more details in . The project consists of two parts: the "Large Scale Liquid Loading Two-phase Flow Tests" campaign carried out at the SINTEF Tiller large scale test facility, and the "Core Model Evaluation and Flow Assurance Risk Study" done by Schlumberger. The experiments are described in more detail in .
The OLGA HD stratified flow model is the next generation flow model for stratified flows, the predominant flow regime in a gas condensate pipeline. In this paper we will validate the OLGA HD 2014.1 flow model against some of the transient and pseudotransient experiments done in the Large Scale Liquid Loading Two-phase Flow Tests campaign.