Summary
The translational velocity, velocity of slug units, is one of the key
closure relationships in two-phase flow mechanistic modeling. It is described
as the summation of the maximum mixture velocity in the slug body and the drift
velocity. The existing equation for the drift velocity is developed by using
potential flow theory. Surface tension and viscosity are neglected. However,
the drift velocity is expected to be affected with high oil viscosity. In this
study, the effects of high oil viscosity on drift velocity for horizontal and
upward inclined pipes are experimentally observed. The experiments are
performed on a flow loop with a test section 50.8 mm ID for inclination angles
of 0° to 90°. Water and viscous oil are used as test fluids. Liquid viscosities
vary from 0.001 to 1.237 Pa•s. A new drift velocity model is proposed for high
oil viscosity for horizontal and upward inclined pipes. The experimental
results are used to evaluate the performances of proposed model for drift
velocity. The calculated drift velocities are compared very well with the
experimental results. The proposed model could be easily implemented into
translational velocity equation. It should improve the existing two-phase flow
models in the development and maintenance of heavy oil fields.
Introduction
High-viscosity oils are produced from many oil fields around the world. Oil
production systems are currently flowing oils with viscosities as high as 10
Pa•s. Current multiphase flow models are largely based on experimental data
with low viscosity liquids. Commonly used laboratory liquids have viscosities
less than 0.020 Pa·s. Multiphase flows are expected to exhibit significantly
different behavior for higher viscosity oils.
Gokcal et al. (2008b) observed slug flow to be the dominant flow pattern for
the high-viscosity oil and gas flows. The knowledge of the slug flow
characteristics is crucial to design pipelines and process equipments. In order
to improve the accuracy of slug characteristics for high-viscosity oils, new
models for slug flow are needed such as translational velocity.
Translational velocity is composed of a superposition of the bubble velocity
in stagnant liquid (i.e. the drift velocity, vd, and the
maximum velocity in the slug body). The research efforts have been focused on
the drift velocity in horizontal and upward inclined pipes.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
6 July 2008
- Meeting paper published:
21 September 2008
- Revised manuscript received:
24 November 2008
- Manuscript approved:
6 December 2008
- Published online:
1 June 2009
- Version of record:
1 June 2009
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