Summary
Oil/gas pipe flows are expected to exhibit significantly different behavior
at high oil viscosities. Effects of high-viscosity oil on flow pattern,
pressure gradient, and liquid holdup are experimentally observed, and
differences in flow behavior of high- and low-viscosity oils are identified.
The experiments are performed on a flow loop with a test section of 50.8-mm ID
and 18.9-m-long horizontal pipe. Superficial liquid and gas velocities vary
from 0.01 to 1.75 m/s and from 0.1 to 20 m/s, respectively. Oil viscosities
from 0.181 to 0.587 Pa·s are investigated. The experimental results are used to
evaluate the performances of existing models for flow pattern and hydrodynamics
predictions. Comparisons of the data with the existing models show significant
discrepancies at high oil viscosities. Possible reasons for these discrepancies
are carefully examined. Some modifications are identified and implemented to
the closure relationships employed in the Zhang et al. (2003) model. After
these modifications, the model predictions provide better agreement with
experimental results for flow pattern transition, pressure gradient, and liquid
holdup.
Introduction
Gas/liquid two-phase flow in pipes is a common occurrence in the petroleum,
chemical, nuclear, and geothermal industries. In the petroleum industry, it is
encountered in the production and transportation of oil and gas. Accurate
prediction of the flow pattern, pressure drop, and liquid holdup is imperative
for the design of production and transport systems.
High-viscosity oils are discovered and produced all around the world.
High-viscosity or "heavy oil" has become one of the most important
future hydrocarbon resources, with ever-increasing world energy demand and
depletion of conventional oils.
Almost all flow models have viscosity as an intrinsic variable. Two-phase
flows are expected to exhibit significantly different behavior for higher
viscosity oils. Many flow behaviors will be affected by the liquid viscosity,
including droplet formation, surface waves, bubble entrainment, slug mixing
zones, and even three-phase stratified flow. Furthermore, the impact of
low-Reynolds-number oil flows in combination with high-Reynolds-number gas and
water flows may yield new flow patterns and concomitant pressure-drop
behaviors.
The literature is awash with two-phase studies addressing mainly the flow
behavior for low-viscosity liquids and gases. However, very few studies in the
literature have addressed high-viscosity multiphase flow behavior. In this
literature review, the state-of-the-art of two-phase flow is first summarized.
Then, the studies addressing the effects of liquid viscosity on two-phase
oil/gas flow behavior are reviewed.
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
15 June 2006
- Meeting paper published:
24 September 2006
- Revised manuscript received:
21 November 2007
- Manuscript approved:
26 November 2007
- Version of record:
15 June 2008
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