Gas Hydrates: Our Energy (and Climate) Future?

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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?

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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

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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

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98 in ocean 2 on land
white dot gas samples recovered black dot
hydrate inferred from seismic imaging dotted
lines hydrate-containing permafrost
http//walrus.wr.usgs.gov/globalhydrate/images/bro
wse.jpg
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using seismic-reflection profiles
Bottom Simulating Reflection (BSRs)
http//woodshole.er.usgs.gov/project-pages/hydrate
s/hydrate.htm
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• Methane Hydrate stability diagram
• methane hydrates can occur at
• water temperatures up to 30C,
• if the pressure is high enough
• -stable over most of ocean floor!

a methane hydrate lattice
redrawn after Kvenvolden (1993)
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The Burning Snowball Methane hydrate
supporting its own combustion
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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 its everywhere
• clean-burning
• natural gas

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• 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 25-30 tcf/yr of natural gas
• India and Japan are leading the charge to hydrate
  recovery

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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
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1 cubic meter of gas hydrate (90 site occupied)
163 m3 of gas .87 m3
Undersea slides (slope failures) may be caused by
methane hydrate dissociation implications for
pipeline?
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Large, expensive pilot programs focus on
drilling in frozen permafrost areas Ex Mallik,
Canada
http//energy.usgs.gov/other/gashydrates/mallik.ht
ml
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New ocean sediment drilling technologies invented
for hydrate recovery and storage
an Ocean Drilling Program core locker with lone
hydrate core in pressurized chamber
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dissociating methane hydrate at sediment/water
interface
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Westbrook et al., 2009
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• 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
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An interesting twist - replace CH4 with CO2 in
the hydrate lattice - have your energy cake and
eat it too?
Park et al., PNAS, 2006
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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.