Gas Hydrates Jeff Chanton, Department of Earth, Ocean & Atmospheric Sciences, Florida State University. Photo by Ian MacDonald

Transcription

1 Gas Hydrates Jeff Chanton, Department of Earth, Ocean & Atmospheric Sciences, Florida State University Photo by Ian MacDonald

2 Gas hydrate, methane hydrate and clathrate Naturally occurring cage-like structures Host molecule = H 2 0 Forms expanded framework with void spaces Guest molecule = CH 4 Fills void spaces Flammable Ice Photo by Rick Coffin

3 Figure from Suess et al., 1999

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6 Gas hydrate A relatively new discovery, first found in nature in 1980 Ratio of 1/6 CH 4 /H 2 O CH 4 /H 2 O volumetric ratio of 164 when dissociated at standard T and P Addition of ethane, propane and butane yield additional hydrate stability ~10% Can be formed from either biogenic microbial methane or thermogenic petro-genic methane. Often found at seep sites ---- Hydrocarbon seeps are natural springs where liquid and gaseous hydrocarbons leak out of the subsurface

7 Gas Hydrate Found in places of 1.low temperature 2.high pressures 3.high CH 4

8 Why do we study hydrates? Methane hydrates represent a future energy resource (if it can be extracted). Methane is a strong greenhouse gas Hydrates have been suggested to have a role in the control of past climates and may affect future climate. Geo-hazard hydrates can destabilize continental slopes and cause submarine slumping

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10 Slide from Ray Boswell

11 From Suess et al., 1999

12 Biogenic Methane Thermogenic Methane

13 Gas hydrate resource pyramid of Boswell and Collett (2006)

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16 The Iġnik Sikumi #1 well is a field trial of a potential gas hydrate production technology that utilizes the injection of CO2 into gas hydrate-bearing sandstone reservoirs, resulting in a chemical exchange reaction that releases methane gas (CH4) while simultaneously sequestering CO2 in a solid hydrate structure as CO2-hydrate.

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18 Nankai Trough Started the flow test and confirmed gas production: March 12, 2013 Ended the flow test: March 18, 2013 Gas flowed 5 days, pipe clogged with sand. Methane hydrate in place, the amount equivalent to approximately 40tcf or approximately 1.1trillion m 3 of methane in the eastern Nankai trough. Equivalent to eleven years of the amount of LNG imported into Japan.

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24 Hydrates in Flow Assurance Hydrates Cause Major Economic & Safety Risks During Energy Production & Transportation Hydrate formation in oil/gas flow lines #1 problem in flow assurance Costly to prevent Costly to remove Safety concern Hydrate plug removed from oil pipeline 24

25 How do we detect gas hydrates? Check for the occurrence of a Bottom Simulating Reflector BSR BSR marks bottom of hydrate occurrence

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28 Acoustic blank or wipe out zones Inline 27

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30 30 cm

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32 SLIDE SHOW 1 Photo Ian MacDonald

33 Chemosynthetic bacteria store elemental S Like fat for when H 2 S supply cut off Photo Ian MacDonald

34 Hydrate stability: seafloor observations Barkley Canyon, Cascadia Margin Observed little morphological change in hydrate outcrops over 1 year (MacDonald et al., 2005)

35 Photo by Charles Fisher Photo by Jonathan Blair Photo by Ian MacDonald Photos borrowed from

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38 Photo Ian MacDonald

39 Photo Ian MacDonald

40 Photo Ian MacDonald

41 Hydrate stability: seafloor observations From Fisher et al., 2000 Are hydrates more stable than predicted by diffusion alone? Kinetic-controlled, surface armoring,.

42 Photo Ian MacDonald Ice worms, a unique life form live in burrows in the hydrate ice

43 Gas Hydrate Stability?

44 Effect on Climate Ice core records show that atmospheric methane concentrations are tightly correlated with temperature over the past 800,000 years. When methane is elevated in the atmosphere, climate is warmer. Massive gas hydrate dissociation may have been an positive feedback factor during hyperthermals such as the Paleocene Eocene Thermal Maximum (PETM).

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46 how do we get a longer record?

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48 Reading the ice archive

49 Reading the ice archive: the gas archive

50 40% anthropogenic increase. 15% 240% anthropogenic increase Human activities have changed the composition of the atmosphere since the pre- industrial era

51 Glacial Period Maximum extent of ice 20,000 years ago (last glacial maximum) Today major continental ice is present on: Antarctica Greenland

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53 Cody scarp

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56 Deep Horizon Oil Spill

57 Daily dose: ~60,000 bbl oil, ~30,000 BOE gas 1500 m 1505 m

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59 Questions?