A Study of Oil/Water Flow Patterns in Horizontal Pipes

Abstract

Summary Oil/water flow-pattern transitions in horizontal pipes have been studied both experimentally and theoretically. A new state-of-the-art oil/water test facility was designed, constructed, and operated. A transparent test section (5.013-cm inside diameter x 15.54 m long) can be inclined at any angle, to study both upward and downward flow simultaneously. Mineral oil and water were the working fluids (µo/µw=29.6, po/pw=0.85, and o=36 dynes/cm at 25.6°C). A new classification for oil/water flow patterns based on published and acquired data is proposed. Six flow patterns were identified and classified into two categories: segregated flow and dispersed flow. Stratified flow and stratified flow with some mixing at the interface (ST&MI) are segregated flow patterns. The dispersed flow can be either water dominated or oil dominated. A dispersion of oil in water over a water layer and an emulsion of oil in water are water-dominated flow patterns. An emulsion of water in oil and a dual dispersion are oil-dominant flow patterns. The oil/water flow-pattern transitions for light oils are predicted using the two-fluid model and a balance between gravity and turbulent fluctuations normal to the axial flow direction. Stability analyses reveal that the stratified/nonstratified transition must be addressed with the complete two-fluid model. Stratified flow is predicted by the viscous Kelvin-Helmholtz (KH) analysis while inviscid KH theory predicted the ST &MI flow pattern. For the dispersed flow pattern, the predicted drop sizes from the Hinze and Levich models are modified to account for the effect of the dispersed phase concentration. The controlling parameter for the coalescence phenomena is the water fraction. The model performance is excellent and compares well with published data. Introduction The need for reliable design methods for multiphase flow has been the driving force behind an extensive research effort in this area, especially for gas/liquid flow, over the past 30 years. Recently, the industry has turned its attention towards the understanding of the simultaneous flow of gas/oil/water mixtures. However, the limiting case where no gas phase is present has received inadequate attention. Dynamic flow characteristics of oil/water mixtures are important in applications such as designing water-lubricated pipelines, production strings in oil wells, and artificial-lift methods. Understanding of oil/water flow behavior in pipes can be crucial in determining the amount of free water in contact with the pipe wall that could cause corrosion/erosion problems. Oil/water flow behavior is also important in arriving at the correct interpretation of the response of production-logging instruments. The performances of separation facilities and multiphase pumps are a strong function of the upstream flow pattern. A knowledge of the distinctive features of oil/ water mixtures, together with those for gas/liquid systems, can be used in the future as a basis to understand the more complex case of gas/oil/water mixtures.

Pressure drop, flow pattern and local water volume fraction measurements of oil–water flow in pipes

“…The experiments were conducted in a 15 m long, 56 mm diameter, inclinable steel pipe using Exxsol D60 oil and water as test fluids. The The observed flow regimes of oil-water flow in horizontal and inclined pipes are catagorized into eight different flow patterns, in accordance with the results presented by Trallero et al (1997), Rodriguez et al (2006) and Lum et al (2006). The different flow patterns observed in oil-water flow are presented in terms of flow pattern maps for different pipe inclinations.…”

“…A high speed camera and a still picture camera were used to visualize the flow. The oil-water flow patterns observed in the present work are in line with the flow pattern classifications proposed by Trallero et al (1997), Rodriguez et al (2006) and Lum et al (2006). The investigated flow cases were categorized into different flow regimes as given in the table 2.…”

“…Most of the previous studies mainly identify the flow patterns and investigate pressure drop variations of oil-water flows. Phase fraction distribution data were seldom measured (Trallero et al, 1997). However, the water volume fraction measurements are of considerable technical importance in twophase oil-water flow systems as it is a key parameter in the prediction of frictional pressure drop.…”

Measurement of oil-water flow via the correlation of turbine flow meter, gamma ray densitometry and drift-flux model

“…About 685 experimental data points are collected, and the range of parameters are given in Table 2. The experimental data consist of the hydraulic pipe diameters in a range from 0.024 m to 0.152 m, and the oil phase viscosities from 1.43 mPa·s to 138 mPa•s [9,[18][19][20][21][22][23][24] . The correlation calculation related to the two systems can be used to establish the follo- The comparisons of the theoretical predictions obtained from Eqs.…”

Calibration of Mineralization Degree for Dynamic Pure-water Measurement in Horizontal Oil-water Two-phase Flow

“…However, in horizontal production profile logging, the oilwater two-phase flow patterns of long distance undulating horizontal well have a mixed flow pattern which is mainly a horizontal segregated flow as opposed to vertical well [17], [18], and flow pattern and velocity are influenced by the inclination of long distance undulating horizontal well, that leads to the pre-existing ring-shaped measuring electrodes of the CWCM being still immersed in oil-water segregated flow when sampling. Although oil-water mixture electrical conductivity could be measured on-line in the process of fluid flow by using the CWCM [19], pure-water phase conductivity could not be obtained by using the ring-shaped electrodes or with a sampler at the condition of oil-water two-phase separation.…”