1 gas hydrate basics. 2 gas hydrates ice-like, crystalline solid may exist at temperatures up to 25...
TRANSCRIPT
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Gas Hydrate basics
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Gas Hydrates
Ice-like, crystalline solid May exist at temperatures up
to 25 °C at high pressure
‘Practical discovery’ by Hammerschmidt, 1934: Hydrates, not ice, were blocking North American gas pipelines
= + 180 Sm3
gas1 m3 hydrate 0.8 m3 water
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Ice-like, crystalline solid May exist at temperatures up
to 25 °C at high pressure
Requirements:- light hydrocarbons (C1-C4)- free water- “low” temperature (offshore: <20 °C )- “high” pressure (offshore: >20 bar)
Gas Hydrates
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Hydrates in cometsMakogon (1987) claimed that Halley’s comet consists of sand, rocks, and large amounts of CO2-hydrates, based on observed gas blowouts when the comet approached the sun.
Photo: MWO Museum Exhibit
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Hydrates in our solar system
Saturn- Average temp: -220°C- Outer ring: hydrate lumps up to 10 m in diameter?
Pluto- Average temp: -230 °C- Methane and water in large amounts
Picture by NASA
Pluto
Charon
Pictures by NASA
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Saturn’s largest moon: Titan
-180°C, liquid methane and ethane
January 2005 Huygens landing Methane hydrate plain?
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Hydrates in the earth
Hydrates exist in enormous amounts in permafrost regions and in deep ocean floors. These in-situ hydrates might:
prove to be enormous energyresources
be a factor in possible global climate change
lead to sea floor instabilities
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Storegga landslide (7-8000 years ago)
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Seafloor hydrate occurrences
ref: Naval Research Laboratory
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Hydrates in petroleum production
A hydrate plug might form about anywhere the conditions are favorable:
wells, X-mas trees, manifolds,jumpers, production pipelines,export pipelines, production risers,export risers, separators, valves, flanges, orifices, dead-legs, instrumentation lines, pipe bends etc.
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Microscopic structure
Structure II hydrate: unit cell
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Water lattice/cavities in hydrates
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Appearance
Ca. 1 cm
Gas system
Oil system
Hydrate crystal
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Hydrate equilibrium
Hydrates
Safe area
Temperature
Pressure Hydrateexistence limit
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Effect of water composition on the hydrate curve
Methane equilibrium curves
0
100
200
300
400
500
600
0 5 10 15 20 25
Temperature [oC]
Pres
sure
[bar
]
Pure water
Sea water (3.5 wt% NaCl)
30 wt% MeOH
30 wt% NaCl
30 wt% MEG
Multiphase Transport
TEMPERATURE
PR
ES
SU
RE
0 m
De
pth
7000 m
1: onshore well
1
WAX
HY
DR
AT
ES
?
2: deep offshore
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Original slide courtesy of Emile Leporcher, TotalOriginal slide courtesy of Emile Leporcher, Total
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Hydrate kinetics
Induction time:hours/days in stabilityregion without hydrates
Growth rates:- heat and mass transfer controlled- influenced by flow
PRESSURE
TEMPERATURE
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Hydrate kinetics
time
Hydrateamount
Induction timeHow long ???
Formation rateHow big ???
Formation periodHow long ???