Effects of monoethylene glycol (MEG) on three-phase flow characteristics in near-horizontal pipes

Abstract

An experimental study is conducted using a 0.152-m ID facility to investigate the effects of the presence of monoethylene glycol (MEG) on three-phase stratified wavy flow in horizontal pipelines. The experiments are conducted under low liquid loading condition, which is very commonly observed in wet gas pipelines. The analyzed flow characteristics include wave pattern, liquid holdup, aqueous phase fraction and pressure gradient.The experimental range of this study covers superficial gas velocity, vSg, values from 8 to 23m/s, superficial liquid velocity, vSL, values of 0.01–0.02m/s, and inlet liquid stream aqueous phase fraction, WCMEG, values of 0–100%. Experiments are conducted with 51wt% of MEG in the aqueous phase, and the results are compared to the case with no MEG, presented by Karami et al. (2016). Differential pressure transmitters, a quick closing valve and pigging system, and a high speed camera are used to acquire the measurements. The trends in the resulting data with respect to input parameters are investigated. The performances of common models and predictive tools are compared to liquid holdup, pressure gradient and aqueous phase fraction experimental results.The observed wave patterns include stratified smooth and stratified wavy with 2-D waves, 3-D waves, roll waves, and atomization flow, with transitions varying by changing the liquid phase. The trends of pressure gradient, liquid holdup, and aqueous phase fraction with respect to vSg, vSL, WCMEG, and wt% of MEG are observed and physical justifications are provided. The predictions of OLGAS 7.1, TUFFP unified model v. 2012, Beggs and Brill (1973), Taitel and Dukler (1976), and Xiao et al. (1990) are compared to the acquired experimental data. The liquid holdup experimental data are under-predicted by all the models, especially for higher WCMEG values. However, the results from OLGAS 7.1 and Xiao et al. (1990) model are in better agreement with experimental data. The three-phase aqueous phase fraction trends are not predicted well. The complicated nature of liquid-liquid interactions causes higher prediction uncertainties. In addition, a statistical analysis is conducted to find the best applicable closure relationships in the modeling of two-phase low liquid loading flow.MEG is used continuously in deep water gas production systems as a hydrate inhibitor. However, MEG mixing in multiphase flow and its effects on flow parameters are not well understood. This paper provides with comprehensive data for three-phase stratified flow for a 0.152-m ID pipe, with MEG in the aqueous phase. In addition, the prediction performance of the commonly used predictive tools in the industry is provided.