Investigation On Flow Characteristic Of Low Liquid Loading Gas-liquid Two-Phase Flow In Horizontal Pipelines

Low liquid loading gas-liquid two-phase flow, which exists widely in gas transmissionpipelines, is one of the typical occurrences of two-phase flow in the oil and gas industry. Innatural gas transmission pipelines, even with initial single-phase natural gas, liquid may beformed in the pipelines by retrograde condensation as a result of pressure decrease. Thesesmall amounts of liquid corresponding to a very small volumetric flow rate fraction may causea much higher liquid holdup and a significant increase in the pressure gradient. The liquidholdups are important factors for determining the pigging frequency and receiving facilities.Accurate pressure gradient prediction is important to selection of the right pipe size andmaterial, and pressure boosting facilities. Water, oil and gas presence predictions at in-situconditions are essential to know whether hydrate or paraffin deposition problem exists or not.The water distribution in the pipeline under certain flow conditions is also important to theanalysis of corrosion occurrence and its prevention with corrosion inhibitors. Therefore, it isvery important to investigate the flow characteristics of low liquid loading gas-liquid two-flowin the transportation of natural gas.For low liquid loading gas-liquid two-phase flow in horizontal pipelines, the governingequations is established based on the gas-liquid momentum equation.The corresponding closerelationship is used to calculate the parameters of the governing equations. Based on theliterature study and theoretical analysis, the mechanism of liquid flow, especially the dropletentrainment mass and momentum transfer process which have a greater impact on the pressuredrop is investigated.The interfacial friction factor is improved which proposed by Fan(2005),and then establish a new, more accurate prediction model which included the dropletentrainment fraction for the low liquid loading gas-liquid two-phase flow in horizontalpipelines. At the same time,a method to divide flow pattern for the low liquid loadinggas-liquid two-phase flow is proposed.The corresponding flow pattern criterion is givenaccording to the experiment data.A solving program in C++Builder6.0platform based on the calculation model isdeveloped in this paper. By the comparative analysis of calculation model and experimental data, it can get that the pressure gradient in estimating error is smaller, indicating theapplicability of this model is well. At last, the effects of pipeline diameter, pipeline inclinationand other parameters on liquid holdup and pressure gradient is analyzed.