1. Gas Hydrates(Burning Ice/Fire in ice) :
Natural Hazard and/
or Natural Resource?
By: Kushank Bajaj
M.Sc.(Tech) Geology
Banaras Hindu University, India

2. Why Study Hydrates ?
1. Factor in Global climate change
2. Future energy resource
3. Sea floor stability

3. From an expedition to “hydrate ridge” off the coast of Oregon
Hydrate Ridge /Barkley Canyon is an accretionary wedge located 90km off the coast of Oregon in the tectonically active
Cascadia subduction zone created by the oblique subduction of the Juan de Fuca Plate beneath the North American Plate
(MacKay et al., 3 1992).
HR is 20km long and 15km wide, and with a northern summit at ~600mbsf, and a southern summit at ~800mbsf
(Torres et al., 2002;).
What are they ?
• Ice like crystalline molecular
complexes
• Guest : Methane, Propane,
Butane etc also CO2.
• Guest type depends on
structure
• Host: water molecules are
bounded by hydrogen forming
cavities
• 1 volume = 150-170 volume of
methane gas
• Low T and High P
• Continental margins &
Permafrost

4. Structure
Stackelberg and Müller
(1954) used X-ray
diffraction and classified
into Type 1 and Type 2
Structures with different
types of cavities.
Two types of cavities :
1. Pentagonal
dodecahedra (512)
(small). Common in
I,II & H
2. Tetradecanhedra
(51262) (large)
Structure I
3. Hexadecahedra
(51264) (large)
Structure II
Ripmeester et al. (1987):
Structure H: 34 water
molecules forming a
hexagonal lattice .
12 A cube,
consisting of 46
water molecules
17.3 A cube
consisting of 136
water molecules
pentagonal
dodecahedra
Tetradecanhedra
Hexadecahedra
Modified after Ripmeester, J. A., Tse, J. S, Ratcliffe, C. I., and Powell, B. M. (1987)
Structure I and II : Isometric(cubic) crystallographic system , where
As ice is always in Hexagonal system.
Structure I : Body centered packing
Structure II: Diamond packing

5. Formation

6. Stability
(Jones et al 2010)
Schlumberger, Oilfield Reviews, 2010

7. Occurrence
Data from Lorenson TD and Kvenvolden KA: A Global Inventory of Natural Gas Hydrate Occurrence, USGS(website)
Recovered are the ones discovered by scientific drilling program and the inferred are by seismic imaging.

8. Indian Scenario
• NGHP 2006
expedition
• 1,894 trillion m3
• 1500 times of
India’s current gas
reserve
Collet et al. 2008

9. Mode of
Occurrence
I. Marine: 95%
A. At or near sea
surface
B. Buried within
the
sediments(upt
o 600m) with
increased
concentration
towards the
gas hydrate
stability zone
II. Permofrost:
5%
Identification
Raman Probe positioned in Barkley Canyon., BC.
NOAA’s Undersea Research Program
Schlumberger, Oilfield Reviews, 2010

10. Nimblett et al., 2005

11. Natural Resource

12. Production
 In lab. 60 to 80% CH4
recovery.
 Exchange reaction
between methane
hydrates and liquid CO2
at the seafloor , Barkley
Canyon, offshore
Vancouver Island.
• With time fluffiness
increases
• 0.5 hrs.: Liq. CO2 & CH4
hydrate
• 42 hrs. : CO2 hydate
&CH4 has
Dunk et al.,2006
Schlumberger, Oilfield Reviews, 2010

13. Major Questions related to methane
hydrate & climate change
1. Why Methane matters?
2. What is the global integrated flux of methane
from permafrost & marine hydrates?
3. What is the potential contribution(as a positive
feedback) of methane hydrate to future climate
change ?
4. Has the past climate ever been affected by
dissociation of hydrates ?
5. What could trigger the dissociation of hydrates?

14. • Is 26 times more potent that CO2 as a GHG
• It has low residence time as it oxidizes to CO2 but it is believed that its residence
time would increase with increase in its concentration.
CH4 + OH = CH3 + H20, CH4Atm OH CH4 residence time CH4 induced warming.
CH4 + O2 = H20 + CO2
• Methane concentration is ~200 times lower than CO2.
• Since pre-industrial times, Methane has increased by ~150 % while CO2 just 40%
(IPCC 2011)
Global flux:
• 7*102 to 1.27* 104 Gt carbon in marine hydrates alone (Deckens, 2011)[Note the
large range and huge amount]
• 3.75*102Gt carbon in methane hydrates on East Siberian Arctic shelf (Shakhova et
al., 2010)
• 1.8*103 Gt of carbon in global hydrate deposits (Boswell & Collett, 2011)
 If 0.1% of CH4 is instantaneously released- CH4 concentration from 1774ppb in 2005
will increase to 2900 ppb
1Gt = 109 tonnes 1 tonne= 103 kg
Some facts about Methane:

15. Major Questions related to methane
hydrate & climate change
1. Why Methane matters?
2. What is the global integrated flux of methane
from permafrost & marine hydrates?
3. What is the potential contribution(as a positive
feedback) of methane hydrate to future climate
change ?
4. Has the past climate ever been affected by
dissociation of hydrates ?
5. What could trigger the dissociation of hydrates?

16. Paleocene Eocene Thermal Maximum
PETM: A past global warming event
• What is it ?
A warming period in which temp at high latitude & deep ocean increased more than 4
degree over less than 10,000 years. (Kennett and Stott, 1991; Zachos et al., 1993).
• Evidences ?
1. –2‰ to–3‰ excursion in d18O of benthic foraminiferaof all oceans and planktic
foraminifera at high latitude locations (Kennett and Stott, 1991;Bralower et al.,
1995; Thomas and Shackleton, 1996; Schmitz et al., 1996)
2. high-latitude interchange of terrestrial mammalian orders (Maas et al., 1995;
Hooker, 1996)
3. prominent extinction of benthic fauna(?) in neritic to abyssal environments (Kaiho
et al., 1996; Steineck and Thomas, 1996; Thomas, 1996)
4. A global expansion of subtropical dinoflagellates
5. input of clay minerals to the ocean indicative of humid conditions (Robert and
Kennett, 1994; Kaiho et al., 1996)

17. • The rapid decrease in carbon
isotope ratios is indicative of a
large increase in atmospheric
greenhouse gases CO2 and CH4
that was coincident with an
approximately 5°C global
warming.
• In theory, additional
greenhouse carbon would have
been absorbed by the ocean,
thereby lowering seawater pH
and causing widespread
dissolution of seafloor
carbonates.(Zachos et al., 2004,
2005).
• Mass-balance calculations
suggest that transfer of 1.4 to
2.8 * 1018 g of CH4 from
oceanic hydrates to the
combined ocean-atmosphere
inorganic reservoir would
explain the observed d13C
excursion during the LPTM
(Dickens et al., 1995). The Palaeocene-Eocene Thermal Maximum as recorded in benthic foraminifer
(Nuttallides truempyi) isotopic records from sites in the Antarctic, south Atlantic and
Pacific ( Zachos et al., 2003 ) , IPCC 2007

18. Probable causes of d13C excursion
1. Intensive volcanic activity, BUT mantle carbon dioxide is not
sufficiently enriched in C 12
2. Terrestrial Biomass, BUT not sufficiently large enough
3. Dissociation of Hydrates- large flux of carbon and its
signature low d13C value (<-60)
A rapid decrease of d13C of 2.5 ‰ over 10000 years imply that an immense quantity of carbon greatly
enriched in C12 was rapidly added to the ocean- atmosphere inorganic carbon reservoir.
Possible causes of dissociation
• Gradual pressure increase due to sedimentary burial
• Submarine slope failure
• Sea level fluctuations
• Increase in bottom water temperature
• Global catastrophic events (meteorites, earthquakes, slumping)

19. Do Methane emission cause climate
change, or do climate fluctuations
cause changes in hydrate stability?

20. Submarine slope failure : Result of
dissociation or a cause?

21. McIver,1982