Summary
Multiphase-flow models for the oil and gas industry are required to
investigate and understand the cocurrent or countercurrent flow of different
fluid phases under a wide range of pressure and temperature conditions and in
several different flow configurations in wellbores, pipelines, and risers and
through the surface facilities. Experimental measurements are required to
develop and validate the multiphase-flow models under controlled conditions and
assess their range of applicability. This is why a large number of
multiphase-flow loops exist around the world. However, there are numerous
varieties of multiphase-flow occurrences because of differences in pressure and
temperature; fluid types; flow regimes; pipe geometry, inclination, and
diameter; and whether the flow is steady-state or transient.
Building a flow loop that reproduces real hydrocarbon wells, including the
reservoir inertia and the complex heat transfer process taking place between
the wellbore and the reservoir, is not feasible. Thus, downscaling typical
field parameters is necessary to study multiphase flows at laboratory
conditions.
This paper presents a critical review of multiphase-flow loops around the
world, highlighting the pros and cons of each facility with regard to
reproducing and monitoring different multiphase-flow situations.
The authors suggest a way forward for new developments in this area.
Introduction
Multiphase flows consist of the simultaneous passage through a system of a
stream composed of two or more phases. They are common natural phenomena; the
flow of blood in our body, the rising gas bubbles in a glass of beer, and the
steam condensation on windows are all examples of naturally occurring
multiphase flows.
However, large-scale multiphase flows, such as those that occur in the
petroleum industry, are difficult to visualize. For example, in a typical
oil-and-gas development, multiphase flow is encountered in the wells, in the
flowlines and risers transporting the fluids from the wells to the platform,
and in the multiphase-flow lines that carry the produced fluids to the
treatment facilities at shore.
Typical parameters for an oil well in the northern basins of the North Sea
are as follows (BERR 2008): production rate of 800–1600 m3/d, tubing
diameter of 0.102–0.130 m, reservoir depth of 3000–3500 m, oil density of
825–930 kg/m3, gas/oil ratio of 100 std m3/std
m3, and water cut up to 90%. For a gas well in the southern gas
basin, the typical parameters become (BERR 2008): initial production rate of
0.7 to more than 2.8 million std m3/d, tubing diameter of
0.114–0.140 m, reservoir depth of 2500–3500 m, and initial liquid/gas ratio of
less than 1 to more than 30 std m3/million std m3. The
operational pressure at the wellhead may reach up to 10 MPa, and reservoir
pressures can be as great as 30 MPa.
However, well-performance values not only vary considerably across the
world, but also vary with time for the same field.
Multiphase-flow systems can be complex because of the simultaneous presence
of different phases and, usually, different compounds in the same stream. Thus,
the development of adequate models presents a formidable challenge. The
combination of empirical observations and numerical modeling has proved to
enhance the understanding of multiphase flow.
Models to represent flows in pipes traditionally were based on empirical
correlations for holdup and pressure gradient. It is more usual now to use
codes based on the multifluid model, in which averaged and separate continuity
and momentum equations are written for the individual phases. For these models,
closure relationships are required for interface and pipe-wall friction.
To complement the theoretical effort, experimental measurements under
controlled conditions are required to verify multiphase-flow models and assess
their range of applicability. This is why a large number of multiphase-flow
loops exist around the world, each with specific capabilities and
limitations.
This paper attempts to review the major worldwide facilities that allow a
wide range of two- and three-phase-flow experiments, but the authors accept
that their review may not be exhaustive. Flow loops may be operated by academic
organizations, independent research centers, or individual companies, and there
is a special category for oil and gas applications, where real hydrocarbon
fluids and field operating conditions are used.
The review is based on information available in the public domain and
focuses on large-scale facilities. This choice reflects the specific need for
multiphase flow loops for studies related to hydrology, petroleum, and
environmental engineering; geothermal energy plants; underground gas storage;
and carbon dioxide (CO2) sequestration. For studies on
nanotechnology, life science, and medical systems, different flow loops are
necessary to reproduce reality in a laboratory. Finally, there are ad-hoc
facilities for the investigation of boiling and condensation processes and for
nuclear-engineering applications.
No flow loop can be representative of all possible situations. Even when
experiments in a given flow loop are believed to be sufficiently exhaustive for
a specific study area, the conditions that will be encountered in a real
application can be different from those recreated in the research facility.
The objective of this paper is therefore to review some of the major
worldwide flow-loop facilities for two- and three-phase-flow investigation that
are reported in the public domain to point out unresolved problems in
reproducing real processes in a laboratory environment.
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
7 August 2007
- Meeting paper published:
11 November 2007
- Revised manuscript received:
18 March 2008
- Manuscript approved:
31 March 2008
- Version of record:
15 September 2008
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