Abstract
An experimental study on highly viscous oil-water two-phase flow conducted in a 5.5 m long and 25.4 mm internal diameter (ID) pipeline is presented. Mineral oil with viscosity ranging from 3.5 Pa.s – 5.0 Pa.s and water were used as test fluid for this study. Experiments were conducted for superficial velocities of oil and water ranging from 0.06 to 0.55 m/s and 0.01 m/s to 1.0 m/s respectively. Axial pressure measurements were made from which the pressure gradients were calculated. Flow pattern determination was aided by high definition video recordings. Numerical simulation of experimental flow conditions is performed using a commercially available Computational Fluid Dynamics code. Results show that at high oil superficial velocities, Core Annular Flow (CAF) is the dominant flow pattern while Oil Plug in Water Flow (OPF) and Dispersed Oil in Water (DOW) flow patterns are dominant high water superficial velocities. Pressure Gradient results showed a general trend of reduction to a minimum as water superficial velocity increases before subsequently increasing on further increasing the superficial water velocity. The CFD results performed well in predicting the flow configurations observed in the experiments.
Highlights
1.1 Background Water usually accompanies crude oil during production especially during enhanced recovery when water is deliberately injected into older or marginal wells to aid production
Characteristic feature of the flow patterns observed in the study are described below with pictures obtained from video recordings shown in Table 2 below: Water Plug in Oil Flow Pattern (WPO): This flow pattern was observed at the lowest water superficial velocity in this study
Similar conclusions were made for CFD simulation comparison with experiments reported by [6] for oil viscosity of 0.28 Pa.s. This implies that the Volume of Fluid (VOF) model is reasonably sufficient for the prediction of flow patterns in oil-water two phase flows for oil viscosity up to 5.0 Pa.s
Summary
1.1 Background Water usually accompanies crude oil during production especially during enhanced recovery when water is deliberately injected into older or marginal wells to aid production. Water is added for lubrication as this reduces pumping requirements for crude transport in cases where heavy or highly viscous oils are involved. Based on the above premise, the study of oil-water flow is essential for production systems design and crude oil pipeline transport networks. The continuous depletion of light (conventional) oil reserves due to long term production has in recent years, increased the attractiveness of unconventional fossil fuels (e.g. shale gas, shale oil and especially heavy oil). The literature is awash with studies of light oils, but scarce in the case of heavy oils. Water is used to assist the flow of highly viscous oils and the study of the flow patterns, pressure gradients, and other characteristics is imperative for heavy oil–water liquid–liquid flows
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