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U N I V E R S I T Y O F B E R G E N
Hydrate Formation and Gas Production from
Hydrates by CO2 Injection
By
Lars Petter Øren Hauge
Institute of Physics and Technology
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Natural gas hydrate
• Crystalized structure consisting of water and a guest
molecule (e.g. methane) – resembles ice
• High pressure (>30 bar) and low temperature (<10 °C)
• Permafrost regions and off-shore
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Ota et al. (2005)
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Estimates of Total Gas Hydrate Amount
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Proven Crude Oil 2010 estimate by EIA
(1358 BBOe)
Most confident estimate by Claudia and Sandler 2005
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Hydrate Reservoir strategies
• Production scenarios
• Pressure reduction
• Temperature increase
• Chemical additive
• Exchange with CO2
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Hydrate Injection of CO2 to produce methane
Pros Cons
• Integrity of hydrate
structure remains intact
• Sequestration of CO2
• No temperature increase
• Increased stability
• Requires permeability
• Risk of hydrate formation
from free water
• Relatively slow rate of
exchange
• Investment cost
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Experimental set up
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Gas supply
High pressure pumps
ISCO pump
Confinement buffer
Bypass valve
Pressure
transducer
Thermocouple
Sandstone core Safety
pressure valve
1/8’’
tubing
MFM
GC
Pressure regulator
Back pressure
valve
Flow control valve
Refrigerator bath Cooling jacket/bath
Circulating antifreeze
Model made by Christian Hågenvik
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Experimental conditions
• Porous media
– Bentheim sandstone
– High permeable (1.1 D)
– 20-25% porosity
– Homogeneous (99% quartz)
• Brine saturation 0.4 – 0.7
• Brine salinity 0.1 – 3.5 wt% NaCl
• Pressurized with CH4 to 83 barg/1200 psi
• Temperature reduced from ~23 °C to 4 °C
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EXPERIMENTAL RESULTS
Methane Hydrate formation
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Same initial conditions (system not dissasembled, only reformed)
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Hydrate formation
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Water saturation based on mass balance and
resistivity
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Post Hydrate formation
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Limiting factor: lack
of water Limiting factor: Mass
transport – water trapping
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Post Hydrate formation
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Higher hydrate saturation for Swi ≈ 0.6
Limiting factor: Mass
transport – water trapping
Limiting factor: lack
of water
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EXPERIMENTAL RESULTS
CO2 induced methane production
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Experimental procedure
• A back pressure valve maintains constant production
pressure of approximately 85 barg.
• CO2, or a CO2/N2 mix, is injected at a constant flow rate
of 1.2 ml/h for all experiments.
• Injection pressure, production pressure, gas fraction and
mass produced is monitored and later used to calculate
differential pressure and fluids produced.
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Fraction of Methane during Production Measured by GC
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Production during CO2 injection Resistivity, gas produced and differential pressure
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Pressure build up
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Remediation of plugged core by use of N2
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N2 pressure
buildup
Inital
CO2 injection
Second CO2
injection
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CO-injection of CO2 and N2 (25/75 mol% resp.)
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Co-injection of
CO2 and N2
N2 pressure
buildup
Injection of
pure CO2
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CO-injection of CO2 and N2 (25/75 mol% resp.)
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Pure CO2 injection
starts
Injected N2 fraction
Injected CO2 fraction
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Methane recovery Free gas in porous media included
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