Performance of a two-phase gas/liquid flow model in vertical wells

Abstract

This paper presents application of a recently developed method for predicting two-phase gas/oil pressure-drop in vertical oil wells. The new method, which is flow-pattern based, is capable of handling flow in both circular and annular channels. Five principal flow regimes-bubbly, dispersed bubbly, slug, churn and annular - are recognized while developing appropriate correlations for predicting void fraction and pressure-drop in each flow regime. Standard oilfield correlations are used for estimating PVT properties of oil and gas: Standing's correlation for solution gas-oil ratio; Katz's correlation for oil formation volume factor; Standing's, and Chew and Connally's correlations for dead and live oil viscosities, respectively; and Lee et al.'s correlation for gas viscosity. A finite-difference algorithm is developed to compute pressure gradient in a wellbore. Computations performed on 115 field tests, involving all the two-phase flow regimes, suggest that the new method performs better than the Aziz et al. correlation. Further comparison of the new method's performance with other standard methods, such as, Orkiszewski, Duns and Ros, Beggs and Brill, Hagedorn and Brown, and Chierici et al., reveals its consistency and improved performance. The test data bank used in this study is that previously used by other authors; thus, validation of the new method is demonstrated with an independent data set.