Hydrate Formation and Gas Production from Hydrates by CO 2 Injection

Transcription

1 U N I V E R S I T Y O F B E R G E N Institute of Physics and Technology Hydrate Formation and Gas Production from Hydrates by CO 2 Injection By Lars Petter Øren Hauge

2 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 Ota et al. (2005)

3 Estimates of Total Gas Hydrate Amount Most confident estimate by Claudia and Sandler 2005 Proven Crude Oil 2010 estimate by EIA (1358 BBOe)

4 Hydrate Reservoir strategies Institute of Physics and Technology Production scenarios Pressure reduction Temperature increase Chemical additive Exchange with CO 2

5 Hydrate Injection of CO 2 to produce methane Pros Integrity of hydrate structure remains intact Sequestration of CO 2 No temperature increase Increased stability Cons Requires permeability Risk of hydrate formation from free water Relatively slow rate of exchange Investment cost

6 Experimental set up Bypass valve Back pressure valve Pressure regulator Flow control valve GC MFM High pressure pumps Gas supply ISCO pump 1/8 tubing Sandstone core Pressure transducer Safety pressure valve Confinement buffer Thermocouple Cooling jacket/bath Refrigerator bath Circulating antifreeze Model made by Christian Hågenvik

7 Experimental conditions Porous media Bentheim sandstone High permeable (1.1 D) 20-25% porosity Homogeneous (99% quartz) Brine saturation Brine salinity wt% NaCl Pressurized with CH 4 to 83 barg/1200 psi Temperature reduced from ~23 C to 4 C

8 Methane Hydrate formation EXPERIMENTAL RESULTS

9 Same initial conditions (system not dissasembled, only reformed) Institute of Physics and Technology

10 Hydrate formation

11 Water saturation based on mass balance and resistivity Institute of Physics and Technology

12 Post Hydrate formation Limiting factor: lack of water Limiting factor: Mass transport water trapping

13 Post Hydrate formation Higher hydrate saturation for Swi 0.6 Limiting factor: lack of water Limiting factor: Mass transport water trapping

14 CO 2 induced methane production EXPERIMENTAL RESULTS

15 Experimental procedure A back pressure valve maintains constant production pressure of approximately 85 barg. CO 2, or a CO 2 /N 2 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.

16 Fraction of Methane during Production Measured by GC Institute of Physics and Technology

17 Production during CO 2 injection Resistivity, gas produced and differential pressure Institute of Physics and Technology Pressure build up

18 Remediation of plugged core by use of N 2 Inital CO2 injection Second CO2 injection N2 pressure buildup

19 CO-injection of CO 2 and N 2 (25/75 mol% resp.) N2 pressure buildup Co-injection of CO2 and N2 Injection of pure CO2

20 CO-injection of CO 2 and N 2 (25/75 mol% resp.) Pure CO 2 injection starts Injected N 2 fraction Injected CO 2 fraction

21 Methane recovery Free gas in porous media included Institute of Physics and Technology

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