Effects of High Oil Viscosity on Drift Velocity for Horizontal and Upward Inclined Pipes

Abstract

Summary The translational velocity, velocity of slug units, is one of the key closure relationships in two-phase flow mechanistic modeling. It is described as the summation of the maximum mixture velocity in the slug body and the drift velocity. The existing equation for the drift velocity is developed by using potential flow theory. Surface tension and viscosity are neglected. However, the drift velocity is expected to be affected with high oil viscosity. In this study, the effects of high oil viscosity on drift velocity for horizontal and upward inclined pipes are experimentally observed. The experiments are performed on a flow loop with a test section 50.8 mm ID for inclination angles of 0° to 90°. Water and viscous oil are used as test fluids. Liquid viscosities vary from 0.001 to 1.237 Pa•s. A new drift velocity model is proposed for high oil viscosity for horizontal and upward inclined pipes. The experimental results are used to evaluate the performances of proposed model for drift velocity. The calculated drift velocities are compared very well with the experimental results. The proposed model could be easily implemented into translational velocity equation. It should improve the existing two-phase flow models in the development and maintenance of heavy oil fields. Introduction High-viscosity oils are produced from many oil fields around the world. Oil production systems are currently flowing oils with viscosities as high as 10 Pa•s. Current multiphase flow models are largely based on experimental data with low viscosity liquids. Commonly used laboratory liquids have viscosities less than 0.020 Pa·s. Multiphase flows are expected to exhibit significantly different behavior for higher viscosity oils. Gokcal et al. (2008b) observed slug flow to be the dominant flow pattern for the high-viscosity oil and gas flows. The knowledge of the slug flow characteristics is crucial to design pipelines and process equipments. In order to improve the accuracy of slug characteristics for high-viscosity oils, new models for slug flow are needed such as translational velocity. Translational velocity is composed of a superposition of the bubble velocity in stagnant liquid (i.e. the drift velocity, vd, and the maximum velocity in the slug body). The research efforts have been focused on the drift velocity in horizontal and upward inclined pipes.

High-Viscosity Oil-Gas Flow in Vertical Pipe

“…Mechanistic models developed for low-viscosity fluids may not be adequate to fully reflect the effect of high fluid viscosity on the performance of gas lift (Schmidt et al 1984), e.g. the effect on the Taylor bubble behaviors (White and Beardmore 1962) including the slug length and the drift velocity (Gokcal et al 2009;Sakharov and Mokhov 2004).…”

Review of oil–water through pipes

“…The need to understand the nature and flow behaviour of oil and water is very crucial since multiphase flow is known to be a complex system and highly problematical due to the existence of various flow patterns and diverse governing mechanisms [30,47]. A lot of researchers [28,31,48,52] tried to simplify and generalizing the liquid-liquid or the two phase flow systems through mechanical models and develop means for predicting the flow patterns, pressure loss, and water holdups. However, the differences in oil physicochemical properties and the various range of operating conditions that subsequently lead to altered hydrodynamics behaviour in the two phase flow system could be huge obstacles in generalizing the two phase flow system.…”

“…In the oil-water two phase flow studies, several empirical and mechanical models were developed [28,31,48,[50][51][52]. However, in developing those models, the flow behaviour requires careful analysis which includes flow stability, fluid physical properties effects, dropsize distribution, pipe material, transition criteria and diameter, buoyancy effect, lower free energy effect at interface and effect of momentum transfer capacity [31,41,53].…”

“…The case of high viscous oil-water in pipeline systems has appeared to play a paramount role in recent studies. Accordingly, many researchers [36,39,52,[60][61][62][63][64] have turned their attentions towards studying high viscous oil-water flow. Since it is known that liquid-liquid behaviour is characterized by the viscosity ratio, thus utilizing the works of low viscosity to high viscosity is not a straight forward step and hence the required parameters cannot be accurately predicted.…”

Research on heavy oil gas lift assisted with light oil injected from the annulus

“…However, considering the physical properties of heavy oil and the complexity of the heavy oil, gas, water three-phase flow, predicting the pressure drop of the multiphase flow of heavy oil is difficult, and some scholars (Zhang and Sarica 2006;Schmidt et al 2008;Gokcal et al 2009;Akhiyarov et al 2010) have presented the models of pressure drop which are suitable for the multiphase flow of heavy oil in a particular situation. But unfortunately those models are not suitable when the physical properties of heavy oil or the environment changes.…”