Talk:Methane clathrate/Archive 1

Archive 1

Natural gas clathrate?

Since it also consists of other gases, similar to natural gas, should this be called "natural gas clathrate"? -- Kjkolb 03:17, 18 December 2005 (UTC)

Dodecahedral

Dodecahedral refers to a solid with 12 faces, not 20 as is stated in the article. Should the value be 20 or 12? --71.227.190.111 20:51, 25 August 2006 (UTC)

The oxygen atoms of the water molecules form the vertices of the dodecahedron, not the faces. A dodecahedron has 20 vertices. —Keenan Pepper 21:48, 25 August 2006 (UTC)

I incorporated that information as it is not obvious to everyone, including me. Thanks for the information.Slicky 15:03, 20 January 2007 (UTC)

A solid form of water?

What source says this is a solid form of water? Isn't it, instead, a sort of compound and not actually water anymore? --Blue Tie (talk) 22:58, 27 January 2008 (UTC)

Dunno the answer (not a chemist), but can tell you that water is "a sort of compound"; in fact, it is a compound. +ILike2BeAnonymous (talk) 23:47, 27 January 2008 (UTC)

How to force a release?

If someone wanted to force a significant (in terms of global warming, etc.) release into the atmosphere, what would be the easiest way to do it? For example, using explosives. Would it take nuclear weapons or would smaller explosive energy succeed? ThVa (talk) 21:50, 15 July 2009 (UTC)

Continental deposits

The article says

necessary conditions are found only either in polar continental sedimentary rocks where surface temperatures are less than 0 °C; or in oceanic sediment at water depths greater than 300 m where the bottom water temperature is around 2 °C.

but later mentions Arctic permafrost deposits of 400 Gt C. Doesn't that imply that polar surface soil is a third environment that satisfies the necessary conditions? --72.136.94.223 (talk) 22:27, 2 November 2008 (UTC)

Hi. Um, I believe it refers to Arctic submarine permafrost. Land-based permafrost also has methane, but not in the form of clathrates. See also clathrate gun hypothesis. Thanks. ~AH1^(TCU) 20:08, 8 November 2008 (UTC)

Please see the image types_of_deposits.gif in USGS page about Methane Gas Hydrates. --CiaPan (talk) 10:54, 26 August 2009 (UTC)

climate change impact of industrial extraction of methane hydrate

Hi, could someone edit this wiki to explain the climate change impact of industrial extraction of methane hydrate? I note James Hansen's concerns about the catastrophic effect of unintentional release if global climate warms to a certain point. But what about any impacts from industrial extraction? Should we be even thinking about touching this stuff? Is it better to leave it where it is and hope like anything we manage to rapidly reduce global emissions in time to avoid Hansen's scenario? Kilinma 07:29, 27 April 2010 (UTC)

Unaware of any existing analysis. However it is simply another source of natural gas. If you must use energy, it will produce CO₂ gas and is probably less "green" that solar. wind or even than nuclear, but more "green" that oil (which produces more CO₂ gas than methane per kilowatt-hr of energy produced) and dramatically more green than coal (which produces the most CO₂ gas than methane per kilowatt-hr of energy produced). Yes, yes, I know - this all depends on how efficient your generating station is, but for state-of-the-art equipment the argument is still pretty on target...

Anyone aware of any literature?

Cheers = Williamborg (Bill) 04:13, 17 May 2010 (UTC)

Methane clathrate subduction

Confirmed or inferred offshore gas hydrate-bearing sediments

The Pacific Ring of Fire - corresponding to subduction zones

It is interesting to note that a number of the known methane clathrate deposits lies in subduction zones (see the two adjacent figures). From this one might infer that the methane clathrate is being subducted and may be contributing to natural gas or oil deposits. Is anyone aware of published literature pertinent to this question? Cheers - Williamborg (Bill) 04:24, 17 May 2010 (UTC)

Reservoir Size

How does one convert from cu meters of Clathrate to tonnes of Carbon? Please help, I tried to validate the number and was out by three orders of magnitude for the 500-2500 Gigatonnes that is mentioned in this article. Frank van Mierlo 20:00, 5 January 2007 (UTC)

Let's see..

The density, δ, of the clathrate is δ = 0.9g/cm³ = 900 kg/m³ That gives that the mass of one m³ of clathrate is m = 900 kg.

m = M*n M = the molar mass of clathrate, n = the number of moles in one m³ M = 1(0.35*12+0.65*13+4*1)+ 5.75(16+2*1)= 120.15 g/mole = 0.12015 kg/mole (As there in each subunit of Clatherane is 1 mole CH₄ and 5.75 mole H₂O and the carbon consit to 35% of C¹² and 65% C¹³)

Thus the number of mole is n = m/M = 7490.63.. mole.

One mole clathrate has consist one mole of carbon --> there are 7490.63.. mole carbon in one m³ of clathrate. The weight of the carbon is m_C = n*M_C where M_C = (0.35*12 + 0.65*13) g/mole --> m_C = 102621.72..g= 102.62..kg

Conclusion: One m³ of clathrate hold 102.62..kg of pure carbon.

Given the estimates of 1×10¹⁵ to 5×10¹⁵ m³ clathrate this would give us between 1*10¹⁷ and 5*10¹⁷ kg in total. This translates to between 1*10¹⁴ and 5*10¹⁴ metric tonnes so eihter I or the one who wrote the article is out by 3 orders of magnitude. I would argue that I am right as 100 kilos of carbon per m³ seems reasonable and from there on it is virtually impossible to make any mistakes in the math. By the same reasoning there would have to be only 0.5 kg per m³ for the article to add upp, an absurdly low number. Either the total reserves of clathrate in m³ or the amount of carbon they hold are wrong.

All numbers taken from the article130.243.153.103 21:55, 28 May 2007 (UTC)

Clathrate deposits are typically only about 1% clathrane by volume. I think this is the bulk of your error. Dragons flight 22:36, 28 May 2007 (UTC)

That would explain most of the error. I'm still a litle high though, if only by twice the amount (between 1*10¹² and 5*10¹² metric tonnes), either way maybe it should be clearly stated that the deposits only contain ~1 % Clathrate?130.243.153.103 10:18, 29 May 2007 (UTC)

I concur that it is important to mention that only 1% by volume of a clathrate deposit is actually methane clathrate. I made a change to that effect. I was surprised to learn that it was! Kencomer (talk) 08:47, 24 December 2007 (UTC)

Isotopic ratio of average earth's carbon is C¹²/C¹³ 98.93/1.07. Where you get 35/65? So 1 m³ of methane clathrate hold only 900 * 12 / 120 = 90 kg of carbon.Qjim (talk) 20:43, 23 April 2008 (UTC)

details seen on the french version of this wiki page (Hydrate de méthane)

Natural Gas Hydrate (NGH)

phase = Solid

Temperature = -20 °C

Density = 0.85 - 0.95

1m³ NGH = 170m³ CH4 & 0.8m³ H2O

Liquefied Natural Gas (LNG)

phase = Liquid

Temperature = -162 °C

Density = 0.42 - 0.47

1m³ of LNG = 600m³ CH4

if it could help for the discution 82.230.69.245 (talk) 22:45, 21 May 2010 (UTC)

Volume ratio of solid methane clathrate to methane gas

After observing (in the lede) that the average methane clathrate hydrate composition is 1 mole of methane for every 5.75 moles of water, and that the observed density is around 0.9 g/cm³, the article continues:

One liter of methane clathrate solid would therefore contain, on average, 168 liters of methane gas (at STP).

This nugget of information has been tagged with {{Citation needed}}. Now this is in fact an elementary calculation, as follows.

For one mole of methane, which has a molar mass of about 16.04 g (see Methane), we have 5.75 moles of water, with a molar mass of about 18.02 g (see Properties of water), so together for each mole of methane the clathrate complex has a mass of 16.04 g + 5.75 × 18.02 g = 119.65 g. The fractional contribution of methane to the mass is then equal to 16.04 g / 119.65 g = 0.134. The density is around 0.9 g/cm³, so one liter of methane clathrate has a mass of around 0.9 kg, and the mass of the methane contained therein is then about 0.134 × 0.9 kg = 0.1206 kg. At a density as a gas of 0.717 kg/m³ (at 0 °C; see the info box at Methane), that means a volume of 0.1206 / 0.717 m³ = 0.168 m³ = 168 L.

Based on WP:CALC, I am inclined to think the tag can be removed, and will do so if there is no disagreement.  --Lambiam 13:03, 8 June 2010 (UTC)

I have replaced the citation needed tag with this note containing your explanation above. To avoid future problems I guess similar calculations could be added in a similar way. -84user (talk) 17:56, 11 June 2010 (UTC)

Japanese production plans & methane ice stability

This blog post has quotes and cites to a number of interesting RS's, regarding (inter alia):

• A methane-ice production experiment in the Canadian arctic, with encouraging results
• Japan's hopes for methane production in their near-offshore
• Interesting evidence on the stability of methane ice, which persists in water at temps up to 50 deg F. This has obvious implications for the worries about methane release due to global warming.

I added a bit re the fuel potential, and there's a nice chart at USGS we should be able to use. I'll come back to this when time permits. Cheers, Pete Tillman (talk) 18:42, 2 December 2010 (UTC)

Natural Deposits, Commercial Use

• "On March 12, 2013 Japan extracted natural gas from frozen methane hydrate off its central coast 50km away the main island of japan in Nankai Trough, the world first and achieved the world's first offshore experiment producing gas from methane hydrate."

This is going to need some work. First, the location is cited in the NY Times as occuring "in an area of the Pacific about 1,000 meters deep and 80 kilometers, or 50 miles, south of the Atsumi Peninsula in central Japan." Second, it's not "the world's fist offshore experiment producing gas from methane hydrate", it's "“the world’s first trial production of gas from oceanic methane hydrates,”" as announced by Toshimitsu Motegi, the Japanese trade minister, again from the NY Times article here. Thoughts? Xin Jing (talk) 16:09, 12 March 2013 (UTC)

References

Carbon - more or less than other fossil fuel reserves

The article led states "The worldwide amount of carbon bound in gas hydrates is conservatively estimated to total twice the amount of carbon to be found in all known fossil fuels on Earth." and cites the USGS. Then in the reservoir size section it says "This estimate, corresponding to 500-2500 gigatonnes carbon (Gt C), is smaller than the 5000 Gt C estimated for all other fossil fuel reserves but substantially larger than the ~230 Gt C estimated for other natural gas sources." and gives 2 references (another belonging to the USGS). Am I mistaken or do they not contradict each other? Coinmanj (talk) 22:56, 15 March 2013 (UTC)

fact that "methane hydrates, in particular, cannot be formed in salt water"?

What about the BPI Horizon in the Gulf of Mexico? Weren't hydrates forming in the intense cold deep waters that kept blocking the repair efforts? — Preceding unsigned comment added by 99.190.133.143 (talk) 01:33, 24 January 2012 (UTC)

• Indeed, methane hydrate did form at the Deep Water Horizon spill. Since most methane hydrates form in salty formation waters, the sentence above is not true. My understanding is that hydrates are more stable in fresher water. As salt is added, the phase transition shifts to colder temperatures (and higher pressures?). In my research group, the equations we use for hydrate stability rely on salinity as well as temperature and pressure. I am editing this section, and will endeavor to find an appropriate and accessible reference.Elriana (talk) 20:32, 16 July 2013 (UTC)

Non microbial Ocean deposits

Methane found in conjunction with oil deposits will bubble up to the surface due to earthquake faults et other natural "fracking" type seismic activity. Although oil deposits off the coast of California have been well known for their undersea oil seepage, those deposits also emit methane. California is known for numerous auxiliary faulting related to San Andreas fault movement/tension. This seepage is in warmer continental shelf so no hydrate forms (oil wells between coast and coastal islands). Gas Hydrates are denser than water ice and have a higher freezing point so >0 (~0) degree water will preferentially form Methane Hydrate in the presence of Methane. Methane Hydrate sinks to the bottom due to higher density, therefore not dependent on surface temp. Two mile thick ice sheets (during ice age), orogeny, faulting, etc not only cause higher underground temp and pressure, coking conditions, turning oil to methane and coal (oil associated with sandstone and shale; coal with slate and quartzite). Note that Methane Hydrate was found at the BP Deepwater Explorer drill site (5000 feet deep in Gulf of Mexico), attributed to difficulties capping the oil spill. Methane Hydrate deposits have been found off the Eastern Seaboard of the US and deep water SE of Florida (e.g. Bermuda trench; thin crust). Shjacks45 (talk) 22:21, 5 April 2013 (UTC)

• Note that the faults need not be seismogenic (producing earthquakes) for them to act as gas conduits. Also, large enough quantities of gas form their own conduits (see Methane chimney), without a need for faulting. This occurs whether the source of the methane is microbial or not. But Shjacks45 makes a good point: thermogenic methane (produced by burial/heating instead of by microbes) behaves the same as biogenic methane, and can form clathrate. Much of the world where hydrates are stable is in the deep ocean, where sediment thickness and crustal age are not sufficient for significant hydrocarbon thermogenesis, but petroleum deposits in the North Sea and Arctic produce thermogenic methane which probably forms clathrate in places.Elriana (talk) 21:57, 16 July 2013 (UTC)

Why doesn't float to the surface?

If methane clathrate has a lower density than water, why doesn't it float to the surface as soon as it is formed? -- 77.7.174.52 (talk) 13:36, 4 November 2010 (UTC)

• Usually clathrate is forming in the sediment pore space. As a solid, it cannot squeeze through the sediments to reach the seafloor and the open water. Within individual pores, the clathrate crystals may float, but they are essentially stuck where they are. One of the concerns regarding clathrate and landslide events is that the slide may rework the sediments, allowing the clathrate to escape, float upward, and dissociate as it reaches warmer waters, releasing a large volume of methane. Scientists are still modeling the physics of this.Elriana (talk) 22:10, 16 July 2013 (UTC)

Can extraction of methane ice cause landslides and earthquakes?

In Dallas (2012 TV series), character Christopher Ewing is looking into alternative energy sources such as methane ice from under the ocean floor but this is problematic for a few reasons. The biggest problems are that extracting the methane from under the ocean floor can cause underwater landslides and even earthquakes. In episode 3, Christopher Ewing seems to find a solution to one or more of these problems, and the solution involves replacing the methane ice with CO2 (either liquefied CO2 or CO2 in solid form, I don't remember). I try to find out if the writers have just made up everything or if some or all of this are realistic. I feel that the earthquake problem has to be fiction and I have no idea about the landslides, but I'm not qualified to make any guesses about anything. What are facts and what are fiction? Urbanus Secundus (talk) 00:25, 21 July 2012 (UTC)

To my knowledge, extraction of 'methane ice' is still not viable on a large scale (see the section above on Japanese production plans and methane ice stability). So the treatment in the TV show is still very much science fiction. That being said, a certain amount of sediment rearrangement is likely in any extraction scheme and could lead to mass wasting events. Whether this mass movement could constitute a 'landslide' is not something we really know, since the effects of such processes would be highly location-dependent. I doubt any earthquakes produced would be high in magnitude, though, since any production would be as close to the seafloor as possible, probably in soft sediments.Elriana (talk) 18:14, 29 October 2013 (UTC)

Ocean Transportation of Hydrate vs. LNG

I don't understand why the sea transportation of hydrate would be more difficult than LNG. It does take up more volume, but since it floats, wouldn't that make solving the problem easier? (ie. pontoons, barges, tug it, etc.) — Preceding unsigned comment added by 207.161.161.77 (talk) 23:34, 1 February 2014 (UTC)

I believe the issue is the stability of methane hydrate. At sea surface temperatures and pressures, it dissociates fairly rapidly and the volume of the mathane gas released is significantly larger than the volume of the hydrate. Any containment vessel would need to be well-engineered and therefore expensive. Anything less than full containment would result in a large cloud of methane around the transport, which would be very flammable. Also, how exactly would the hydrate have gotten to the surface? If you want to harvest what's below the seafloor, that isn't in big ice-berge-like chunks; it's usually in sediment pore space. If you are talking about making hydrate instead of LNG as a transport mechanism, I think any gains you get from it floating are countered by the problems with keeping it stable. At the point at which you've built a pressure tank for transport, it's more efficient to store the stuff in its densest form. Elriana (talk) 20:36, 3 February 2014 (UTC)

Expert needed

I have added {{expert-subject|Physics|talk=Expert needed|reason=important subject needs better treatment than this}} to the article. I believe the whole article needs a careful review, but here are some areas to look at:

• confusing terms hydrate and clathrate need clearer definition and use
• graph needs better explanation than I can give
• uncited claims of "hydrate is stable at atmospheric pressure to a temperature of approximately 0 °C" needs fixing (it contradicts the diagram)

-84user (talk) 17:23, 11 June 2010 (UTC)

Note. The uncited claim referred to above was removed in this edit, so don't go looking for it in the article as it is now. It should be replaced, though, by accurate and verifiable information about under what conditions stable solid crystals form.  --Lambiam 11:29, 12 June 2010 (UTC)

I added a question (below) re phase-temperature diagram scale. Walkingstick3 (talk) 14:40, 25 February 2015 (UTC)

Temperature-Pressure phase diagram scale

The numeric scale for temperature has no zero (no problem, but it made me curious) and shows irregular intervals, sometimes incrementing by one, elsewhere by six! This seems improper for any graph, where the line on the graph perhaps should adapt to the scale. Walkingstick3 (talk) 14:40, 25 February 2015 (UTC)

The line on the phase diagram is empirically derived (i.e., not from theory or equations). I don't know why they used a variable temperature scale in this particular case, but both logarithmic and variable spacing on axes are not that unusual in empirical phase diagrams. The choice of spacing is usually made either to make a trend more obvious or to fit a large range of values onto an axis without losing resolution in the ranges of most interest to the user. If someone can find a phase diagram for methane clathrate that has evenly spaced axes and the appropriate copyright permissions, the current phase diagram can be replaced. None of the plots I have are public/reproducible. Elriana (talk) 20:17, 27 February 2015 (UTC)

Methane clathrates and climate change

GHG potential figures are old. From IPCC AR 5 figures are ~28x and 84x CO2 for 100 yr and 20 yr timeframes. I can reference if someone is prepared to change it. Other sources estimate as high as 104x CO2-e. — Preceding unsigned comment added by 60.224.228.49 (talk) 16:23, 24 February 2015 (UTC)

List those references, please. So long as the units and methods are consistent, an update to the figures in the newest IPCC report shouldn't require any more discussion.Elriana (talk) 20:27, 27 February 2015 (UTC)

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How likely is an earthquake to trigger a methane release

Storegga_Slide#Possible_mechanism says an earthquake might have caused hydrate expansion. - Can this article say if/how/when that is possible ? - Rod57 (talk) 11:47, 10 March 2017 (UTC)

Basic chemical formula

I found no information on this article or anywhere else on the internet regarding the basic chemical reaction formula when utilizing methane clathrate for generating energy. Is it combustion with atmospheric oxygen? What is the waste gas when utilized? Is it methane or carbon dioxide? — Preceding unsigned comment added by Nnnu (talk • contribs) 00:49, 28 September 2015 (UTC)

? the methane will be oxidised/burnt (using air) producing water vapour and CO₂ ? - Rod57 (talk) 11:53, 10 March 2017 (UTC)

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Eh Value for Methanogenesis

Obviously an oversight, the Eh value given for methanogenesis was listed as < 400 mV. I have adjusted it to read between -350 mV -450 mV. — Preceding unsigned comment added by 70.52.152.76 (talk) 03:04, 31 July 2006 (UTC)

Spoiler award granted for MC in popular fiction section!

I might get back to this after finishing the book... — Preceding unsigned comment added by 62.78.161.132 (talk) 19:55, 8 January 2008 (UTC)

Methane Clathrate and permafrost

The Methane clathrates and climate change section relates methane-clathrate release to melting permafrost. I think this should be clarified to emphasize that this is submarine permafrost, i.e., on the ocean floor, since "permafrost" by itself has a terrestrial connotation. If there are no objections in the next couple of days, I will edit the section to fix this. — Preceding unsigned comment added by 24.61.9.152 (talk) 05:38, 5 May 2020 (UTC)