Summary
Drift-flux modeling techniques are commonly used to represent two and
three-phase flow in pipes and wellbores. Unlike mechanistic models, drift-flux
models are continuous, differentiable and relatively fast to compute, so they
are well suited for use in wellbore flow models within reservoir
simulators. Drift-flux models require a number of empirical parameters. Most of
the parameters used in current simulators were determined from experiments in
small diameter (2 inch or less) pipes. These parameters may not be directly
applicable to flow in wellbores or surface facilities, however, as the flow
mechanisms in small pipes can differ qualitatively from those in large pipes.
In order to evaluate and extend current driftflux models, an extensive
experimental program was initiated.
The experiments entailed measurement of water-gas, oil-water and
oil-water-gas flows in a 15 cm diameter, 11 m long plexiglass pipe at 8
deviations ranging from vertical to slightly downward. In this paper, these
experimental data are used to determine drift-flux parameters for steady state
two-phase flows of water-gas and oil-water in large-diameter pipes at
inclinations ranging from vertical to near-horizontal. The parameters are
determined using an optimization technique that minimizes the difference
between experimental and model predictions for holdup. It is shown that the
optimized parameters provide considerably better agreement with the
experimental data than do the existing default parameters.
Introduction
Multiphase flow effects in wellbores and pipes can have a strong impact on
the performance of reservoirs and surface facilities. In the case of horizontal
or multilateral wells, for example, pressure losses in the well can lead to a
loss of production at the toe or overproduction at the heel. In order to model
and thereby optimize the performance of wells or reservoirs coupled to surface
facilities, accurate multiphase pipeflow models must be incorporated into
reservoir simulators.
Within the context of petroleum engineering, the three types of pipeflow
models most commonly used are empirical correlations, homogeneous models and
mechanistic models.
Empirical correlations are based on the curve fitting of experimental data
and their applicability is generally limited to the range of variables explored
in the experiments. These correlations can be either specific for each flow
pattern or can be flow pattern independent. Homogeneous models assume that the
fluid properties can be represented by mixture properties and single-phase flow
techniques can be applied to the mixture.
© 2005. Society of Petroleum Engineers
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History
- Original manuscript received:
4 June 2003
- Revised manuscript received:
1 November 2004
- Manuscript approved:
11 November 2004
- Version of record:
15 March 2005
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