Evaluation of the Behavioral Characteristics in a Gas and Heavy Oil Stratified Flow According to the Herschel-Bulkley Fluid Model.

Abstract

At present, most researches on gas–liquid two-phase flow use a power-law fluid model. However, with the development of unconventional petroleum resources and the restarting of heavy oil, the fluid showed strong yield characteristics. The power-law constitutive will not be able to express the yield-pseudoplastic fluid rheological properties. In order to make the study applicable to a larger range of shear rates, this study used the Herschel–Bulkley fluid model to discuss the gas–liquid flow characteristics. Based on the Herschel-Bulkley fluid constitutive, a two-fluid model, combined with dimensionless and iterative calculation methods, was used to theoretically derive the prediction model of liquid holdup and pressure drop for gas–liquid stratified flow. The effects of non-Newtonian fluid rheological parameters, flow conditions, and pipeline geometry on Herschel–Bulkley fluid and gas stratified flow were further analyzed. The results show that the power-law index n and the yield stress τ0 (characterizing the rheological characteristics of the liquid phase) have significant effects on the gas–liquid two-phase stratified flow. Specifically, the enhanced liquid yield and shear thinning characteristics will lead to an increase in liquid holdup and a decrease in pressure drop. Comparing with the experimental data, the calculation model proposed in this work has a good prediction effect and provides new insights into the flow behavior of gas and waxy heavy oil with yield stress.