Presentation on theme: "Gas Hydrates: Our Energy (and Climate) Future?"— Presentation transcript:
1 Gas Hydrates: Our Energy (and Climate) Future? Lecture Outline:What are gas hydrates anyway?Gas hydrates as an energy source – pros and consGas hydrates and climate change: adding fuel to the flames?
2 Hydrates - What are they? Gas Hydrates are solids formed from hydrocarbon gas and liquid waterThey resemble wet snow and can exist at temperatures above the freezing point of waterThey 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 anotherHydrates 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 ocean2% on landwhite dot = gas samples recoveredblack dot = hydrate inferred from seismic imagingdotted 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 phenomenaThis phenomena allows a quantification of the amount of hydrates presentBlanking –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 velocity3.3 km/s. Which produce a strong signal. (http://www.pgc.nrcan.gc.ca/marine/hydra.htm#ref )
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 latticeredrawn 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 gasthere is A LOT of it,and it’s everywhereclean-burningnatural gas
10 USA has gas hydrate reserves of 112,000-676,000 trillion cubic feet (tcf) USA has 2,200 tcf of natural gas reserves (EIA)USA uses tcf/yr of natural gasIndia and Japan are leading the charge to hydrate recovery
12 An Energy Coup for Japan: ‘Flammable Ice’ Water depth: 1000msubfloor depth: 300mNYTimes, 3/12/13
13 Methane Hydrates as an energy source PROBLEMS:hydrate dissociation upon recovery; engineering challengeexpense of long pipelines across continental slope, subjectto blockage with solid hydrate-methane release into atmosphere problem for climate change(20x more potent than CO2)fragile ecosystems surroundsediment surface hydrates& seepsice worm that lives in hydratephoto by Ian Mc Donald
14 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 m3Undersea slides (slope failures) may be caused by methane hydrate dissociation;implications for pipeline?
15 Large, expensive pilot programs focus on drilling in frozen permafrost areasEx: Mallik, Canada
22 lots of CH4 escaping from melting gas hydrates-powerful positive feedbackon global warming-CH4 is a powerful greenhouse gas-most likely oxidizes to CO2 beforeit enters the atmosphere… but still!see Archer et al., 2007 fordetailed investigation ofmethane hydrate dissociationduring global warmingWestbrook et al., 2009
23 - 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
24 Take-home pointMethane hydrates represent the largest fossil fuel reservoir,but problems ranging from yet-to-be-developed technologies and climate change feedbacks remain to be resolved.