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

This paper (SPE 115342) was accepted for presentation at the 2008 SPE Annual Technical Conference and Exhibition, Denver, 21–24 September, and revised for publication. Original manuscript received for review 6 July 2008. Revised manuscript received for review 24 November 2008. Paper peer approved 6 December 2008. 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.