1. Gas Hydrates: Our Energy (and Climate) Future?
Lecture Outline:
What are gas hydrates anyway?
Gas hydrates as an energy source – pros and cons
Gas hydrates and climate change: adding fuel to the flames?

2. Hydrates - What are they?
Gas Hydrates are solids formed from hydrocarbon gas and liquid water
They resemble wet snow and can exist at temperatures above the freezing point of water
They belong to a form of complexes known as clathrates

3. Clathrates - What are they?
Clathrates are substances having a lattice-like structure or appearance in which molecules of one substance are completely enclosed within the crystal structure of another
Hydrates consist of host molecules (water) forming a lattice structure acting like a cage, to entrap guest molecules (gas)
CH4 (most common), CO2, H2S form hydrates

4. 98% in ocean
2% on land
white dot = gas samples recovered
black dot = hydrate inferred from seismic imaging
dotted lines = hydrate-containing permafrost

5. using seismic-reflection profiles
Bottom Simulating Reflection (BSRs)
BSR – (bottom simulating reflection)
Interface between the free methane and the gas hydrates cause the BSR phenomena
This phenomena allows a quantification of the amount of hydrates present
Blanking –
The cementation effect of the hydrate causes a lower signal to be sent back to the ship.
Allows quantification of the hydrate zone.
Hydrate acoustical velocity
3.3 km/s. Which produce a strong signal. ( )

6. Methane Hydrate stability diagram methane hydrates can occur at
water temperatures up to 30°C,
if the pressure is high enough
-stable over most of ocean floor!
a methane hydrate lattice
redrawn after Kvenvolden (1993)

7. “The Burning Snowball”
Methane hydrate supporting its own combustion

9. Methane Hydrates as an energy source
BENEFITS:
- 1 cubic meter of gas hydrate (90% site occupied) = 163 m3 of gas
there is A LOT of it,
and it’s everywhere
clean-burning
natural gas

10. USA has gas hydrate reserves estimated between 112000 tcf and 676,000 trillion cubic feet (tcf)
USA has 1400 tcf of natural gas reserves
USA uses tcf/yr of natural gas
India and Japan are leading the charge to hydrate recovery

11. Methane Hydrates as an energy source
PROBLEMS:
hydrate dissociation upon recovery; engineering challenge
expense of long pipelines across continental slope, subject
to blockage with solid hydrate
-methane release into atmosphere problem for climate change
fragile ecosystems surround
sediment surface hydrates
& seeps
ice worm that lives in hydrate
photo by Ian Mc Donald

12. 1 cubic meter of gas hydrate (90% site occupied) = 163 m3 of gas +
1 cubic meter of gas hydrate (90% site occupied) = 163 m3 of gas m3
Undersea slides (slope failures) may be caused by methane hydrate dissociation;
implications for pipeline?

13. Large, expensive pilot programs focus on drilling in frozen
permafrost areas
Ex: Mallik, Canada

16. New ocean sediment drilling technologies
invented for hydrate recovery and storage
an Ocean Drilling Program core locker
with lone hydrate core in pressurized chamber

18. dissociating methane hydrate at sediment/water interface

19. Westbrook et al., 2009

20. lots of CH4 escaping from
melting gas hydrates
-powerful positive feedback
on global warming because
CH4 is a powerful greenhouse gas
-most likely oxidizes to CO2 before
it enters the atmosphere… but still!
see Archer et al., 2007 for
detailed investigation of
methane hydrate dissociation
during global warming
Westbrook et al., 2009

21. - replace CH4 with CO2 in the hydrate lattice
An interesting twist:
- replace CH4 with CO2 in the hydrate lattice
- have your energy cake and eat it too?
Park et al., PNAS, 2006

22. Take-home point
Methane hydrates represent the largest fossil fuel reservoir,
but problems ranging from yet-to-be-developed technologies and climate change feedbacks remain to be resolved.