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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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