<DrumBeat: February 7, 2009 The Oil Drum Depletion Thoughts #1 - Sunk Costs and the Endowment Effect>

70 comments on Offshore LNG Generation

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totoneila on February 7, 2009 - 4:35am Permalink | Subthread | Parent | Comments top

Hello Rockman,

Thxs for this keypost. I am quite the admirer of your expert postings here on TOD.

http://www.hydrocarbons-technology.com/features/feature46255/
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The Sweet in the Sour [Nov. 28, 2008]

..About a third of the world's natural gas reserves contain high concentrations of contaminants and so are termed 'sour gas'.

..Low levels of contamination pose few problems but the higher concentrations in sour gas demand more intensive, more expensive processes.

..In the past Shell has tended to develop gas fields with low contamination, but still has 25 highly contaminated sites in production. Some 30% of Western Canada's reserves are sour, for example, but the scale of the challenge in the Middle East is far greater.

The UAE holds the world's fifth-largest gas reserves – approximately 214 trillion cubic feet – of which a large proportion is sour.

..Many factors push up the cost of exploiting sour gas reserves, most notably the fact that its contaminants make it highly poisonous, adding to health and safety concerns. It is also highly corrosive to iron, threatening flow lines and production equipment with sulphide stress cracking.
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Much more info in this article. Some natgas fields contain up to 35% H2S!.

I am not a natgas expert, but I believe if the natgas is sour [contains Sulfur], that this S must be removed before the compression stage or LNG stage, as the sulfur is quite corrosive and lethally toxic as hydrogen sulfide gas.

This requires much additional processing and safety equipment, especially on any next-generation floating natgas processing ship, because the workers would have no good survival options if the boat accidently became enveloped in toxic fumes. Hydrogen sulfide gas is heavier than air so it would tend to accumulate in any low spots on a ship. Even jumping overboard wouldn't help if you could not hold your breath long enough to swim out/escape the toxic layer.

http://en.wikipedia.org/wiki/Sour_gas
http://en.wikipedia.org/wiki/Hydrogen_sulfide
http://en.wikipedia.org/wiki/Amine_gas_treating
http://en.wikipedia.org/wiki/Claus_process

I would assume a natgas processing ship would be regularly offloading the hot and molten sulfur [Amine + Claus Process] to regular scheduled cargo ships as sulfur is a key industrial Element, and at one recent point was selling for $900/ton. Thxs for any reply.

Bob Shaw in Phx,Az Are Humans Smarter than Yeast?

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ROCKMAN on February 7, 2009 - 8:32am Permalink | Subthread | Parent | Comments top

toto,

It can be a little unnerving working around H2S. I've been on wells drilling sour gas sections and you don't sleep well. An FSOP flaring 20 million cf of NG a day is a scary place too. But H2S can be a curse or a blessing. There have been times when the S market is high and operators make a nice bonus on the recovery process. I haven't watched the S market in some time. But $900/ton sounds likes a strong market. If Shell et al believe the market is stable they might push development on those sour fields where it was only the H2S content holding them back.

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AshenLight on February 8, 2009 - 4:32am Permalink | Subthread | Parent | Comments top

As a biologist that works with H2S, I have to wonder if there's an economical way to use microbes to remove it from the gas. There are many different sulfide oxidation pathways that yield different end products (not just elemental S but polysulfides, thiosulfate, polythionates, etc.) which are less toxic and potentially easier to remove.

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ROCKMAN on February 8, 2009 - 6:22pm Permalink | Subthread | Parent | Comments top

Maybe Ashen but I suspect scalabilty and the time factor might be the difficulty with such an approach. A few thousand cf per day perhaps but 25 million cf per day is a lot to deal with. The NG has to be processed right then and quickly. No way to store any appreciable amount of NG in a gaseous state in an offshore environment.

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totoneila on February 9, 2009 - 1:16am Permalink | Subthread | Parent | Comments top

Rockman, Thxs for your reply.

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Engineer-Poet on February 9, 2009 - 10:27am Permalink | Subthread | Parent | Comments top

Instead of processing the H2S to elemental sulfur, it may make more sense to process it to H2 by reaction with molten copper (the copper sulfide is regenerated by burning the sulfur off with air).  The hydrogen can then be reacted with CO2 to make methanol.

I'd like to see the gas composition from some of these high-H2S fields.  If they also produce a fair amount of CO2, then even more of the gas product could be turned into commodities.

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70 comments on Offshore LNG Generation

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