reply to post by Scalded Frog
Right now I'm watching the feeds from Enterprise ROV 2 and Skandi ROV 1, and I can only say that except for the "fins", the lower part of the LMRP
cap ("top hat") is completely obscured by the gushing oil/gas/hydrate mix. (I'll call it "oil" for short but we'll keep in mind that it's not
About 12 hours ago, one of the Skandi ROVs was showing this gush of oil and another ROV (Ent 2 maybe?) was on the other side of the cap and that side
was quite visible. So it seems to me there are a minimum of two possibilities here.
1) As another poster suggested, perhaps there are wide variations in the rate the oil is gushing out. Sometimes it's huge and sometimes it's worse
than huge. This variation could be due to whatever is happening down-hole by way of debris, or could be some anomaly in the reservoir's pressure in
the region where the well was drilled through the top of the dome.
2) The exact camera position will certainly make a difference. The cap is not seated level. It is noticeably tilted and off-center. That is not
surprising, because as we all saw before BP replaced the cap, the top of the pipe had deteriorated and had a chunk missing out of one side of the
piece that extends vertically above the top of the BOP. (We were of course unable to see the pipe that is inside the BOP but it's not unreasonable to
assume that it also might have deteriorated to some degree.)
Now, the oil is not only gushing straight up, a percentage of it is also able to spew out to one side. Naturally, because it's a "sideways" release
of oil, the fluid dynamics involved mean that the "sideways pressure" may be less that the upward pressure. All the same, we're looking at a lot of
pressure that is being exerted on one section of the inside of the cap's "walls". Naturally, this forces the cap off-center. The rest of the oil
gushes up into the cap's cone-shaped upper section, where some of it gets picked up by the pipes there and is taken up to sea level for "capture".
The rest has nowhere to go, so it billows out around the lower edges of the cap.
Again, quite naturally, the oil will find the path of least resistance, and where the cap's base is higher (due to the tilt), more oil billows out
there than elsewhere. I believe this means that the cap is probably working less efficiently than before. Gut instinct tells me that something that's
seated off-line and tilted won't work as well as a similar object that's seated flush and centered. I base this assumption by imagining the
degree of such a situation, taken in stages:
(1) If the cap is sitting flush (level) and is centered, the oil will escape around its lower edge at even pressure and the turbulence and abrasive
actions of any debris in the oil will also be evenly distributed. This gives the cap the best chance of capturing oil in its upper section at a
regular rate and allows it to be taken off via the pipes there. It also means that abrasive wear on the cap and its components will be as evenly
distributed as possible.
(2) If the cap is tilted a few degrees and slightly off-center, the oil will tend to escape at the higher part of the lower edge and the turbulence
and related abrasion will therefore be greater there than elsewhere. (The abrasion is now worse in some place than in the 1st case.) As the tilt means
that there is now less effective capture volume inside the cap, it might affect the amount of oil that is captured in the upper section.
(3) If the cap is severely tilted then the turbulence (and pressure and abrasion) will be far more concentrated on one side of it. Also, the capture
volume inside the cap is now considerably less. Also, some sections will now have very severe abrasion risk while others will have far less than when
it was level.
(4) The nth
degree: if the cap is tilted to 90 degrees, then virtually no oil is now being captured and the pressure on one side of it would
probably push the whole thing away from the top of the BOP. (Now, abrasion risk no longer matters.)
This is why I think that the cap is no longer working as well as it did before. It just makes sense that it cannot
work as well as it did. I
also think that they were well aware that this would be the outcome of the "refit". The people involved in setting up the refit are not stupid,
after all. They have some very good engineers and they'd know the ins and outs of all this far, far better than I would.
For this reason I suspect that this cap was put back on as a temporary measure and they are now designing a new one that will balance better and allow
for more oil capture.
One way to do this would be to fit a cap that does not have a straight (level) lower edge -- meaning that from the side, it will be gradually longer
in one half than in the other half. (The base of the cap would therefore look elliptical rather than circular.) Also, in the half of the cap that is
facing to the damaged part of the pipe, it would be good to fit another capture pipe.
This means the cap would not only have a pipes in the top but in one side as well. In fact, they could fit three, spaced at 120 deg intervals. By
adjusting the rate those pipes collect the oil, they could help to balance the pressures on the inside of the cap and have a better chance of keeping
it centered. Obviously they'd also have to fit devices to prevent clogging but at least it would improve the chances of collecting the oil and
keeping the thing in place.
Apologies for the long rave. I'm still on first coffee. Meanwhile...
For BP, this tilted cap might have some advantages. If they wish, they can give the MSM video images from the side of the cap that is tilted downwards
and where there is (therefore) less oil belching out, and effectively present a less-than-accurate picture of the real situation.
Of course, I'm not suggesting that BP would deliberately try to mislead the public in this way...
[edit on 25/6/10 by JustMike]