Evaluation of Two-Phase-Flow Correlations and Mechanistic Models for Small-Diameter Pipelines at Slightly Inclined Downward Flow

Abstract

Summary In this study, two-phase-flow pressure-prediction correlations and mechanistic models for pipelines commonly used in the petroleum industry are evaluated against experimental data. Downward two-phase flow occurs in hilly-terrain pipelines, in steam-injection wells, and in offshore oil- and gas-production systems. During pipeline design and simulation, experimental data are usually unavailable to calibrate against correlations and models. Sometimes, it is difficult to determine which correlation or model to use in predicting pressure gradient in inclined downward flow because very few correlations and models were developed specifically for downward pipe flow. Experimental data used in this study are from published papers (Kokal and Stanislav 1989a, 1989b). Experimental data were gathered from 1-, 2-, and 3-in. pipes with seven inclination angles. Oil and air were used as testing fluids. During the experiment, superficial-liquid velocities (SLVs) range from 1.2 to 10 ft/sec and superficial-gas velocities (SGVs) range from 0.76 to 85 ft/sec. The experimental results were plotted as pressure gradient vs. SGV for each SLV. Beggs-Brill (BB), Dukler-Eaton-Flanigan (DEF), Dukler-Flani- gan (DF), Dukler, Eaton, and Eaton-Flanigan (EF) correlations and the Xiao mechanistic model are evaluated in this study. The results of this study can be used as guidelines in choosing two-phase-flow pressure-prediction correlations and models in designing and analyzing downward two-phase-flow pipelines.