Numerical study of dispersed oil–water turbulent flow in horizontal tube

In this paper, the three-dimensional flow of two immiscible liquids in a horizontal pipe has been investigated numerically. The transient numerical simulations of two-phase dispersed flow in a pipe (of ID = 0.0024 m) have been carried out using commercial CFD package FLUENT 6.2 in conjunction with multiphase model. Oil–water system is selected as the two-phase system in this work. The k − ε model was used to describe the turbulence in continuous phase. The numerical results in terms of the phase distribution profiles and average in-situ hold-up are presented and discussed. The predicted results are seen to be in good agreement qualitatively as well as quantitatively with the previous experimental results available in the literature.     

A homogeneous model for gas–liquid flow in horizontal wells

Radial influx or outflux stands for the major difference between fluid flow in a pipe and fluid flow in a well. A homogeneous model for gas–liquid flow in a horizontal well is presented in this paper. In addition to frictional and gravitational components of total pressure drop, accelerational pressure drops due to fluid expansion and radial influx or outflux are considered. Effect of radial influx or outflux on wall friction is also taken account for. With a segmented approach, the new model and several existing pipe flow models have been applied to predict pressure drop along a wellbore, and predictions are compared with experimental data. It is found that the new homogeneous model outperforms existing models for gas–liquid flow in horizontal wells.     

Effect of drag-reducing polymers on horizontal oil–water flows

The effect of a drag-reducing polymer (DRP) in the water phase during horizontal oil–water flow was investigated in a 14 mm ID acrylic pipe. Oil (5.5 mPa s, 828 kg/m³) and a co-polymer (Magnafloc 1011) of polyacrylamide and sodium acrylate were used. Two polymer concentrations were tested, 20 ppm and 50 ppm, made from a 1000 ppm master solution. The results showed a strong effect of DRP on flow patterns. The presence of DRP extended the region of stratified flow and delayed transition to slug flow. The addition of the polymer clearly damped interfacial waves. Annular flow changed in all cases investigated to stratified or dual continuous flow, while slug flow changed in most cases to stratified flow. In the cases where the slug and bubble flow patterns still appeared after the addition of the polymer, the oil slugs and bubbles were seen to flow closer together than in the flow without the polymer. The DRP caused a decrease in pressure gradient and a maximum drag reduction of about 50% was found when the polymer was introduced into annular flow. The height of the interface and the water hold up increased with DRP. There were no large differences on pressure gradient and hold up between the two DRP concentrations. Using a two-fluid model it was found that the addition of the polymer results in a decrease in both the interfacial and the water wall shear stresses.