Abstract

The pipeline flow behaviour of unstable oil-in-water and water-in-oil emulsions has been studied over a wide range of experimental conditions. The effects of flow rate, pipe diameter and the dispersed phase concentration have been determined.

In laminar flow, oil-in-water emulsions behaved like Newtonian fluids when the dispersed phase concentration was less than 55%. At higher concentration, they behaved like non-Newtonian fluids and the viscosity was dependent upon the pipe diameter. Water-in-oil emulsions were found to be Newtonian in the range of dispersed phase concentration studied. (maximum concentration studied was 41%). The effect of pipe diameter on the viscosity of water-tn-oil emulsions was important only at higher concentrations (esp. 41%).

In turbulent flow. oil-in-water emulsions behaved like Newtonian fluids (and the turbulent flow viscosity of these emulsions could be predicted by Einstein is equation) whereas water-in-oil emulsions behaved like drag-reducing fluids.

Inversion of oil-in-water emulsion to water-in-oil emulsion occurred at a very high dispersed phase concentration (77.5%) -whereas inversion of water-in-oil emulsion to oil-in-water emulsion occurred at: a lower dispersed phase concentration (41.7%).

Based upon the experimental data. a scale-up correlation for predicting pressure losses In turbulent flow of water-in-oil emulsions Is proposed

Introduction

Emulsions are dispersions of two immiscible liquids. for example. oil and water. There can be two different kinds of emulsions depending upon whether oil is the dispersed phase or water is the dispersed phase. When oil is the dispersed phase. the emulsion is called an oil-in-water (abbreviated O/W) emulsion and when water is the dispersed phase. the emulsion is called a water-in-oil (abbreviated W/O) emulsion.

Both O/W and W/O emulsions are encountered in various operations in the petroleum industry such as oil-well drilling [1–5]. oil-well fracturing and acidizing [6]. primary oil production [7–9]. secondary and tertiary oil production [7–9). pipeline transportation of highly viscous crude oils (in the form of O/W emulsions) [10–181 and down-hole emulsification operations (for increasing the rate of viscous crude oil production) [19–21]. Emulsions are also being used as tools for enhanced oil recovery [22].

Although emulsions are encountered. in so many oil production operations, they have not been widely studied. In particular, an in-depth study of pipeline transport characteristics of emulsions has not been done. This prompted the undertaking of the present study which had the following major objectives:

  • to study the transport characteristics of various concentrated unstable O/W emulsions.

  • to study the transport characteristics of various concentrated unstable W/O emulsions.

  • to develop a pressure loss correlation for the emulsions.

LITERATURE REVIEW

Most of the previous research work has been restricted to the study of flow patterns in concurrent oil-water flow [23–27]. For the study of frictional losses in pipes, special attention has been given to laminar stratified flow [28–32] and laminar concentric flow [33]. Both experimental and theoretical work has been reported for these flow regimes.

Gengel, et al. [14] studied the laminar and the turbulent flow behaviour of unstable o/W emulsions. The oil phase concentrations studied varied from O% to 50%.

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