Hi Stephen,
Perhaps the membrane could be spread out on the surface of the water
just before ice begins forming - such that one can avoid the rough
underside of the ice rupturing the membrane. And one could have some
kind of circular floating barrier (pykrete*?) around the perimeter of
the whole area to prevent the ice from distorting in the usual way.
This barrier would be anchored to the bottom - as can be done for
floating oil rigs.
We could then think of the possibility to thicken the ice within the
perimeter, e.g. by pumping water onto the membrane to freeze in the cold
Arctic air, and then building up layers of ice above that, especially
around the edges (because one wants the methane to collect in the centre).
Cheers,
John
* Pykrete is very strong under compression - like concrete. Hence you'd
have a ring of it, and struts perhaps.
---
On 21/06/2011 12:24, Stephen Salter wrote:
John
The design of gas catching equipment is strongly affected by coverage
area and flow rate. I have been looking at slow gas seepage over
large areas, say a 50 by 150 metre rectangle . I can transport and
deploy something that is compact for transport but can be spread out
on the sea bed to form something like a distorted parachute. The
volume of gas we can store underwater is small.
The words 'blow out' imply something much smaller but with much higher
flows and pressures and the design would be very different. I think
that we may need quite a wide range of quite distinct bits of
equipment. We also need to understand source areas and flow rates
that are likely to be encountered.
I do like the idea of letting the ice do the structural work but I
have seen film of quite rough ice undersides and lots of breaks.
Stephen.
Emeritus Professor of Engineering Design
Institute for Energy Systems
School of Engineering
Mayfield Road
University of Edinburgh EH9 3JL
Scotland
Tel +44 131 650 5704
Mobile 07795 203 195
www.see.ed.ac.uk/~shs
On 21/06/2011 11:39, John Nissen wrote:
Dear Peter,
Thanks for your reply. Stephen has suggested a means of capturing
methane, which would catch the oil as well, using a large area of
plastic membrane held down at its edges by weighted tyres (or
something just heavier than water). It wouldn't solve the general
problem of natural blow-out, e.g. in ESAS, which concerns Shakhova et
al. (2008) [1], because you would not know in advance where the
blow-out might take place; but it could solve the problem when there
is drilling on a particular site - so the blow-out is restricted to a
limited, known area (less than say 1 km-2). The membrane would be
submerged and held over the danger area (anchored by the weights)
when the sea ice has retreated. In a blow-out, the gas would push
the membrane up to the surface - under the ice if there is ice - with
the weights still holding down the edges. So you'd get something
looking like an underwater hot-air balloon! You could then capture
or destroy the oil and gas when the ice has retreated. Is this the
kind of thing that the industry is thinking about?
Cheers,
John
---
On 21/06/2011 09:07, P. Wadhams wrote:
Dear John, Generally the assumption is that if there is an under-ice
blowout, oil and gas will come out together, with the oil droplets
coating the gas bubbles and being carried up by them. So the result
is a bubble plume carrying oil up to the surface. Industry and
government people concerned with coping with this emphasise the
importance of the oil as a pollutant, and treat the gas as either
something that can be allowed to escape from the surface, or
something that can be ignited. There is no specific programme to
deal with a gas leak as such, Best wishes Peter
On Jun 21 2011, John Nissen wrote:
Dear Peter,
This [1] could be relevant to your workshop on oil under sea ice,
late September in Italy.
Does anybody know how they'd deal with major gas (methane) leak
when drilling in the Arctic? This would be relevant to our
"methane busting" workshop, London, 3-4 September, where we will
brainstorm on methods to prevent potentially huge quantities of
Arctic methane reaching the atmosphere. Who is an expert on gas
leaks, that we could invite?
Cheers,
John
---
[1] http://planetark.org/wen/62377
A major offshore Arctic oil spill could severely challenge the
Coast Guard, with no available infrastructure to base rescue and
clean-up operations, the Coast Guard commandant said on Monday.
"There is nothing up there to operate from at present and we're
really starting from ground zero," said Adm. Robert Papp Jr. "Now's
the time to be not just talking about it, but acting about it."
Several major oil companies, notably Royal Dutch Shell, have
acquired leases to drill in the Beaufort and Chukchi seas off
Alaska. Arctic waters are likely to be accessible to humans for
longer periods as the planet heats up.
In May, the extent of Arctic ice was the third-smallest since
satellites began collecting data in 1979, according to the U.S.
National Snow and Ice Data Center.
Noting that the Coast Guard sent 3,000 people to work on the 2010
BP oil spill in the Gulf of Mexico, Papp told reporters at a
government symposium on shrinking Arctic ice: "No way we could
deploy several thousand people as we did in the Deepwater Horizon
spill."
The Coast Guard has no helicopters based on Alaska's North Slope,
and no U.S. agency has a helicopter there equipped to perform
rescues at sea, he said. There are no facilities that could serve
as temporary hangars for equipment, or any small boat facilities.
Housing for any emergency workers amounts to a few dozen hotel
rooms, he said.
LIQUID FUEL TURNS TO GEL
Even as the Arctic warms -- and it is warming faster than lower
latitudes -- temperatures are still extremely cold, which means
equipment built for operations in temperate zones need to be tested
for fitness in the far north.
For example, the Coast Guard flew a basic military cargo plane, the
C-130, in the Arctic and found that the craft's liquid fuel turned
into a gel when temperatures dipped below a certain level unless
heaters were applied to it, Papp said.
Only one U.S. icebreaker ship will be under way this year, he said.
Another is being decommissioned and a third ship is being updated.
Papp said China is building what will be the most powerful
conventional icebreaker in the world.
He praised the signing last month of the Arctic Search and Rescue
Agreement, where eight Arctic nations -- Canada, Denmark, Finland,
Iceland, Norway, Russia, Sweden and the United States -- agreed to
cooperate on rescues above the Arctic Circle.
The United States also needs to ratify the Law of the Sea treaty,
Papp said. He said other Arctic nations are using this pact to
stake claims to swaths of the extended continental shelf in the
Arctic, and that U.S. ratification would enable the United States
to extend its sovereignty there as well.
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