Home > Wet Gas Multiphase Services > Multiphase Loop
In 1998, CEESI began the operation of a wet-gas test facility that used natural gas and a hydrocarbon liquid as the flowing fluids.
The facility has been in continuous use for over 8 years performing various experimental tests on flow metering systems, gas-liquid separators, and other specialized instrumentation.
In 2004, CEESI built a small scale (2") multiphase test loop where natural gas, hydrocarbon liquid and fresh water could all be flowing at the same time.
From this small pilot test, it was determined that the large wet-gas facility could be converted to multiphase flow without incurring too many severe problems.
The natural gas industry uses the term multiphase flow whenever natural gas, hydrocarbon liquid and water are flowing together.
In reality this is not true multiphase flow because there are no solids present.
A more correct definition would be two-phase flow with multi-component liquids.
However the industry definition is in wide use and will also be used in this discussion.
The block diagram shows the major components of the multiphase test facility.
The loop can be pressurized using an outside source of natural gas.
Once the loop is pressurized, the natural gas is moved around the test loop by the circulation compressors.
The only heat source is the "heat of compression" produced by the circulation compressors.
This amount of heat is sufficient to warm all of the metal piping to a temperature several degrees above ambient.
The heat exchanger is then used to maintain a stable temperature during any experimental test.
In the past, experimental tests have been conducted with temperatures ranging between 70°F and 125°F.
Once the flowing temperature has become stable, the natural gas mass flow rate is determined by the "gas flow measurement" package which consists of a turbine meter, an ultrasonic meter, and a gas chromatograph.
The turbine meter and the ultrasonic are different pipe sizes and as such, they produce different pipeline velocities.
The gas chromatograph is a dual column device capable of producing a C9+ analysis.
Using this gas composition and the measured pressure and temperature at the turbine meter and the ultrasonic meter, the mass flow rate can be determined at each meter.
Since the same amount of gas is flowing through each meter, the mass flow as determined by each meter needs to be in very close agreement or something is in error and must be corrected.
The mass flow of the natural gas remains constant as it flow around the loop.
The pressure, temperature, and pipe diameter can change which will affect the actual velocity or volumetric flow; but the mass flow remains the same.
The liquids are injected into the pipeline downstream of the gas flow measurement package.
The liquids are then carried along with the natural gas through the tests sections where the items being tested are installed.
After passing through the test sections, the liquid is separated from the natural gas at the gas-liquid separator.
The gas returns to the compressor inlet and is recompressed and recirculated.
The liquid falls to the bottom of the gas-liquid separator and is collected in a storage vessel below the separator.
Either hydrocarbon liquid or fresh water (or both) is withdrawn from the liquid-liquid separator by means of positive displacement pumps.
The mass flow and density of each liquid is measured by coriolis meters before being injected into the natural gas stream.
As the liquid is being injected into the test loop, the liquid collected at the gas-liquid separator will then flow into the liquid-liquid separator.
The liquid-liquid separator is sized such that it is capable of doing a very good job of separating the hydrocarbon liquid and water.
Tests have shown that (at the maximum liquid flow rates) the water content in the hydrocarbon stream is less than 40 PPM.
Likewise the amount of hydrocarbon liquid in the water stream is less than 40 PPM.
All of the necessary information is now known to compute the various parameters associated in multiphase flow.
The gas composition and the gas mass flow rate are known; and the actual volumetric flow can be determined at any location in the test section from the pressure and temperature at that location.
The liquid mass flow rate and density is known from the coriolis meters.
The only assumption that is being made is that there is very little mass transfer between phases.
That is, the gas stays gas and the liquid stays liquid.
Tests have shown that this assumption is valid as long as the pressure drop from the liquid injection point to the gas-liquid separator does not exceed 8%.
The following table lists the capabilities of the CEESI multiphase test facility as it now exists.
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ENGLISH
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UNITS
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METRIC
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UNITS
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PRESSURE |
200 - 1100
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psia
|
1.28 - 7.6
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MPa
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TEMPERATURE |
70 - 125
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°F
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21-52
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°C
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NATURAL GAS FLOW |
7 - 75
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ft/s
(4" Sch 80 Pipe)
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2.0 - 23
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m/s
(97.18mm Pipe)
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|
|
0.56 - 6.0
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ACFS
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0.016 - 0.17
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m3/s
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|
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2020 - 21600
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ACFH
|
57-612
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m3/h
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|
|
3.7 - 42
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mmSCFD
(1100 psia)
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|
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HYDROCARBON LIQUID FLOW |
0.02 - 6.4
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lb/s
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0.01 - 2.9
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kg/s
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|
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0.2 - 60
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GPM
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0.75 - 227
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lpm
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0.00045 - 0.13
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ACFS
|
0.000013 - 0.0037
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m3/s
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|
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1.6 - 481
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ACFH
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0.045 - 13.6
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m3/h
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7 - 2060
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BPD
(Barrels Per Day)
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FRESH WATER FLOW |
0.0055 - 8.3
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lb/s
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0.0025 - 3.76
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kg/s
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0.04 - 60
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GPM
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0.15 - 227
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lpm
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0.000089 - 0.13
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ACFS
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0.0000025 - 0.0037
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m3/s
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0.319 - 481
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ACFH
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0.0091 - 13.6
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m3/h
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1.4 - 2060
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BPD
(Barrels Per Day)
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* Standard Conditions: P = 14.73 psia T = 60°F