Handling the worst-case blowout

[docellen]

This is a continuation of a closed-out discussion on
http://www.theoildrum.com/node/6740/679161 See also the thread
"Disposing of excess oil" for another proposal.

Assumptions:
1) We have an emergency threatening severe environmental damage, but
not loss of life. (Oil gushing at the sea floor.)
2) We have a way to connect a new riser and collect all the oil at the
bottom.
3) We don't know exactly what ratio of gas and oil is in the release.
It seems to vary.
4) The flow rate seems to be increasing. We can't shut it off. All
we can do is divert it.

Requirements:
1) Minimize release of oil to the environment.
2) Minimize release at the sea floor.
3) Minimize risks to personnel, including heat, explosion, and smoke
inhalation during construction and operation.
4) Keep the design simple, using readily available parts if possible,
readily constructed parts if necessary, nothing that will take weeks
to build.
5) Plan for bad weather, including worst-case, a direct hit from a
hurricane.

At this point, I don't have a specific design worked out, just some
ideas involving a riser supported with underwater pontoons, and maybe
a valve that can direct the flow left or right so that a diver may
work in the area. I don't even know how deep to put the pontoons and
valve. This would be a compromise between needing to avoid bad
weather and not making things too difficult for divers.

[docellen]

on July 17, 2010 - 7:36am fdoleza wrote:
<blockquote>
Docellen, the best layout would be as follows, I think:

Take a dynamically positioned semi, strip the deck, put in an 80,000
BOPD process train. To bring the fluids to the surface, install a
tower at the sea floor, with piling to keep it fixed, because this
tower will have a flex joint at the top, and then a 10,000 psi working
pressure riser pipe going up to about -300 feet, where you can have a
manifold and connectors for a set of high pressure flexible lines
which connect to a manifold set on the semi.

The semi has to be equipped with the equipment to separate oil and
gas, because the gas has to be flared. So you need to put in a very
large set of flare booms.

To offload the oil, a tanker with bow thursters has to come in from
the upwind side, so it's better to put a very large boom crane
somewhere in the tail end of the semi, which is going to be right
where the quarters building is, so this is going to require a little
thought, because the choppers have to land and need clearance or they
run into the crane. But I think i can get around that.

So, this really large boom, say 300 ft long, is used to hand over the
hose to the tanker, which uses its thrusters to make sure it doesn't
bump the floater. It loads the oil, and moves off.

I think this is a pretty good layout, it'll take a couple of years to
get it done, though.
</blockquote>

Maybe less than two years, if we say no more drilling until it is
ready. :>)

How about instead of a special manifold 300 feet underwater, we use
standard TEE connectors, spaced 500 feet apart, and a line of 12-inch
pipe extending as long as it needs to handle the entire flow. At each
TEE, we have a valve and a smaller pipe to the surface. The
connectors at the surface could be available for whatever ships can
handle some of the flow. When the weather gets bad, the ships move
away, and leave flares sticking up maybe 20 feet from the top of the
waves.

Good discussion. Lot's of details to be worked out, how to keep the
flares burning in a high wind, etc.

[MacQuigg]

See the thread "Floating flare" for a sketch of how we might build a
flare from readily-available parts.

One thing we might want to add to the piping system you suggest is a
gas separator ahead of the flares. I don't know if existing equipment
is available, but at least we could have a big tank where we draw off
the gas at the top, and the oil maybe a foot above the bottom. That
should give us a steady pressure with relatively clean oil for the
flares or the collection ships.