Two-Phase Slug Flow Experiments with Viscous Liquids
Doctoral thesis
Permanent lenke
http://hdl.handle.net/11250/2390031Utgivelsesdato
2016Metadata
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Sammendrag
The challenges behind the multiphase transport of oil and gas mixtures are increasing as
the oil and gas industry is moving towards production from non-conventional reservoirs
and in remote locations. Transport of high viscosity fluids in long multiphase pipelines is
a particular challenge. Previous experiments have shown that gas-liquid slug flow is a
frequent two-phase flow pattern at high liquid viscosities. The slug flow regime is an
unstable flow, which may lead to operational problems, as the slug lengths and velocities
can become very large. Most of the available experimental data and flow models are based
on low viscosity fluids, and therefore, the computational models have some uncertainty
regarding the viscous effects.
With this in mind, the main objective of this thesis is to extend the knowledge of the twophase
flow transport of slug flow with viscous liquids by experimental work, data analysis
of available information and evaluation of certain flow concepts within slug flow models,
such as bubble propagation, wake effect, severe slugging stability, and flow regime
transition.
All the experiments were carried out at the Multiphase Flow Laboratory of the Norwegian
University of Science and Technology and the experimental data were used to evaluate
the performance of existing models. Dedicated set-ups and measurement methods were
designed for each of the studied phenomena. Instrumentation has included an array of
video cameras with image analysis, as well as external and internal impedance ring
probes.
Flow stability was evaluated for gas-liquid severe slugging in a lazy wave shaped riser
with different liquid viscosities. The experimental results show flow stability at lower gas
velocities as the liquid viscosity is increased.
The history effect of the flow in an upstream pipe connected to a downwards inclined
pipe was studied. The results confirm the existence of a metastable region in the flow
regime map where both stratified and slug flow can be stable flow regimes depending on
the flow pattern at the inlet. This effect is stronger for liquids that are more viscous. It is
demonstrated that slug tracking models in principle can capture this phenomenon.
The bubble propagation velocities for horizontal flows at Reynolds numbers for laminar
flow and for transition to turbulent flow have been measured. An empirical correlation for estimation of the bubble front velocity in the full range from laminar to turbulent flow
is suggested, based on the experimental results.
The wake effect between two consecutive bubbles in laminar horizontal flow has been
measured. In comparison with the turbulent case, an earlier interaction of the bubbles was
observed in terms of the slug length between them.
A new multi-beam gamma densitometer was also designed and fabricated to measure
three phase fractions along the cross-sectional area of acrylic pipes. The new gamma
densitometer is subject to additional testing.
Further works might address to extend the metastable region study to include stronger
pipe inclinations and much longer pipes, in order to verify the sustainability of the slugs
generated on this region. Moreover, additional sensitivity studies can be made with
dynamic slug tracking models, regarding the effects of the bubble velocity relations and
the wake effect on the simulations of the slug flow evolution in a pipes.
Består av
Paper 1: Experiments on Severe Slugging in a S-Riser System with Viscous Liquids. Mariana. J.C. Diaz, Andreas H. Akselsen, Ole Jørgen Nydal - Is not included due to copyrightPaper 2: Severe slugging with viscous liquids: experiments and simulations. Mariana J.C. Diaz, Milad Khatibi, Ole Jørgen Nydal - Is not included due to copyright
Paper 3: Inlet Effects on Flow Regimes in Downwards Inclined Pipes. M. Diaz, O.J. Nydal - Is not included due to copyright
Paper 4: Bubble Translational Velocity in Horizontal Slug Flow with Medium Liquid Viscosity. Mariana J.C. Díaz and Ole J. Nydal
Paper 5: Inlet Effects on Gas-Liquid Flow Regimes in Downwards Inclined Pipes. Mariana J.C. Diaz and Ole J. Nydal. - Is not included due to copyright
Paper 6: Wake Effect on the Slug Bubble Velocity: Experiments in Laminar Flow. Mariana J.C. Díaz and Ole J. Nydal