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What is Multiphase Flow?
Case-studies. Liquid-Gas Flows:
Flow Pattern
Some Practical Solutions
Challenges involving flow assurance
Vertical Two-Phase Flow
Horizontal Two-Phase Flow:
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
What is Multiphase Flow?
Some Practical
Solutions
Interacting flow of two or more phases, where the interface
between the phases is influenced by their motion
Oil
Water
Gas
Flow Assurance
Importance of studding multiphase flow:
• Need to optimum design
• Prediction of operational limits
• Safety of plant operation
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
What is Multiphase Flow?
Some Practical
Solutions
Multiphase flow
• The number of the variables affecting the pressure drop is enormous:
thermodynamics parameters and variables describing the interaction
between the phases.
• Compressibility - density depends on the actual flowing pressure and
temperature.
• Frictional pressure losses are much more difficult to describe, since more
than one phases is in contact with the pipe wall.
• Slippage loss - The great difference in densities of the liquid and gas
phases and the tendency of the gas phase to overtake or slip-by the
liquid phase.
• Pressure losses considerably vary with the spatial arrangement in the
pipe of the flowing phases
Challenge in multiphase flow - To predict the pressure drop along the pipe.
Flow Assurance
Vertical Two-Phase Flow
…
Bubble flow Slug flow Churn flow Annular flow Wispy Annular
Bubble Flow - the liquid is continuous and there is a dispersion of bubbles
within the liquid;
Slug or Plug Flow - the bubbles have coalesced to make larger bubbles
which approach the diameter of the tube;
Churn Flow - the slug flow bubbles have broken down to give oscillating
churn regime;
Annular Flow - the liquid flows on the wall of the tube as a film, with some
liquid entrained in the core, and the gas flows in the centre;
Wispy Annular Flow - as the liquid flow rate is increased, the concentration
of drops in the gas core increases, leading to the formation of large lumps or
streaks (wisps) of liquid.
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
Some Practical
Solutions
Flow Assurance
Video
Horizontal Two-Phase Flow
Bubble flow
Annular flow
Elongated bubble flow (Plug)
Slug flow
Stratified flow
Stratified wavy flow
Stratified Flow - the gravitational separation is complete;
Stratified Wavy Flow - the surface becomes unstable and waves appear on it;
Elongated Bubble Flow - large bubbles flowing near the top of the tube;
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
Some Practical
Solutions
Incre
asin
g f
low
speed
Flow Assurance
Definition of Flow Pattern
…
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
Some Practical
Solutions
Flow Assurance
Horizontal Two-Phase Flow Pattern
Challenges involving Flow Assurance
Emulsions
Slugging
Sand
Hydrates
Wax / Paraffin deposition
Scale
Fluid control
Flow control
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
Flow Assurance
Some Practical
Solutions
Slugs
Asphaltenes
Wax
Scales
Hydrates
Corrosion
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
Some Practical
Solutions
Flow Assurance
Challenges involving Flow Assurance
Some Practical Solutions to Assure Flow
Problem Solution
Asphaltenes Asphaltenes inhibitors
Scales Inhibitors and pigging.
Hydrates Hydrates inhibitors
Wax 1. Hot oiling for flow line cleanup can be cost
effective if the paraffin is totally removed and
stays in solution in the oil used at separator
temperature.
2. Regular pigging
3. Solvent or condensate treatments
4. Chemicals can be applied
Corrosion To cool the fluids prior to entry to the pipeline. An
alternative is to use corrosion resistant pipe for
the initial sections of the pipeline
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
Some Practical
Solutions
Flow Assurance
Problem Solution
Slugs Slug avoidance:
Heavy slugging can be avoided by design or
operational changes. Smaller diameter pipelines
can reduce slugging;
Another solution often used on-shore is to install
a big slug catcher at the receiving facilities.
Slug control:
Active use of the topside choke;
Artificial gas-lift
Increase gas injection on the well;
What is Multiphase Flow?
Case-studies: Liquid-Gas Flows
Some Practical
Solutions
Flow Assurance
Some Practical Solutions to Assure Flow
12
References: 1. Barnea, D. (1987) A unified model for predicting flow-pattern transitions for
the whole range of pipe inclinations, Int. J. Multiphase Flow, 13, 1-12.
2. Dukler, A. E. and Taitel, W. (1986) Flow Pattern Transitions in Gas-Liquid
Systems: Measurement and Modelling, Chapter 1 of Multiphase Science and
Technology, Vol. 2 (Ed. G. F. Hewitt, J. M. Delhaye and N. Zuber),
Hemisphere Publishing Corporation.
3. Hewitt, G. F. (1982) Chapter 2, Handbook of Multiphase Systems (Ed.
G. Hetsroni), Hemisphere Publishing Corporation, New York.
4. Hewitt, G. F., Martin, C. J. and Wilkes, N. S. (1985) Experimental and
modelling studies of annular flow in the region between flow reversal and the
pressure drop minimum, Physico-Chemical Hydrodynamics, 6, 43-50.
5. Lin, P. Y. and Hanratty, T. J. (1986) Prediction of the initiation of slugs with
linear stability theory, Int. J. Multiphase Flow, 12, 79-98.
6. Taitel, Y., Barnea, D. and Dukler, A. E. (1980) Modelling flow pattern
transitions for steady upward gas-liquid flow in vertical tubes, AIChE J, 26,
345-354.
7. Bratland O. (2009) Pipe Flow 2 – Multiphase Flow Assurance