Model for Simulating Large Wave Regime in Gas-Liquid Pipe Flow

Abstract

Multiphase transport in the oil industry is becoming important as new oil and gas fields which are discovered often are less accessible. Multiphase transportation is required over longer distances at deeper sea levels, and the ability to predict flow behavior in these conditions is needed. In order to be able to predict stresses caused on the pipeline by the flow, this thesis will look into the wavy flow regime and attempt to develop a model that can predict properties such as frequency, wave length and wave speed of the developed waves in the two-phase (liquid and gas) pipe flow. The wave model presented in this thesis is built around the work of George Johnson. The discontinuous wave model presented in his work is the basis for the model in this thesis. A new shock condition is introduced, which focuses on getting a more physical relationship between the liquid height at the tail of the wave and the wave height at the top of the wave. A High Definition Stratified Flow Model (HD-model) has been developed by SPT Technology Center in Schlumberger, former known as SPT Group. The HD-model is designed to give more reliable predictions of pressure drop and liquid inventory in pipelines. 3D-simulations are too computer intensive to be practical, and the lack of velocity distribution in a 1D model renders the crucial wall and interface friction terms undetermined. The HD-model resolves the inconsistency of 1D models by accounting for 2D velocity distribution over the pipe cross section, in combination with the 1D conservation equations. As a result, this would yield a 3D flow description.Predictions made from the wave model were compared with the experimental results presented by Johnson. The comparisons were done by using three different versions of the model. One where frictions from the HD-model and the modified shock condition were used, one where only the modified shock condition was used together with friction factors as used in Johnson, and one where shock condition and friction factors were identical to what Johnson used in his work.Deriving a conclusion from the comparisons made in this thesis was difficult, because of some shortcomings in the wave model, but the predictions from the model with frictions from the HD-model and the modified shock condition, showed to be slightly more consistent with the experimental results.