A Model for Interpretation of a Re-Start Experiment of Viscous Oil-Water Annular Flow

A.C. Bannwart, A. Barbosa, and G.S. Ribeiro (Brazil)

Keywords

Transient analysis, pipe flow, oilwater flow, restart, experiments, modelling.

Abstract

The pipeline transportation of viscous oils using water assisted flow technologies such as core-annular flow has been recently proposed for the exploitation of heavy oil reserves. The viscosity reduction obtained thanks to lubrication by water is significant since the pressure drop in steady core-annular flow becomes comparable to water flow only. However, oil adhesion onto the pipe wall may occur for certain crudes and oleophilic pipe materials, possibly resulting in severe fouling of the pipe. Adhesion effects may be particularly critical when re-starting the pipeline after an unwanted, sudden stop of core-annular flow. In this work, we present the results of a re-start experiment where an initially stable horizontal oil-water annular flow was suddenly stopped for 60 hours then re started with water only, until pressure drop reaches its final value for single-phase water flow. The oil used is a 4,000 mPa.s, 999.2 kg/m Brazilian crude. The initial oil holdup was 0.85. The pipe is predominantly horizontal with 2.8 cm i.d., partly made on commercial steel and glass (for flow visualization). A physical model based on the mass and momentum conservation equations during the re-start process is proposed to interpret experimental results 3 .

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