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View Diary: BP LiveBlog - Diary 11 (303 comments)

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  •  cutting off the riser (0+ / 0-)

    The riser may be reducing the flow somewhat, but not that much.   The riser is a big fat pipe with an open end.   There is a little bit of a constriction where it has bent over and crimped.

    Thing is, we might have a leak in the BOP that might be comparable to forcing the flow through a 4" diameter hole, given that they were trying to overwealm the leak by pumping mud through a 4" diameter hose.   Then it goes through a roughly 21" diameter pipe.    Perhaps the crimp is equivalent to a 4" by 28" wide pipe, much bigger cross section than the original hole.     The flow from the original hole spreads out and slows down in the riser pipe then has to speed up again to get through the crimp and gets tangled up with itself going around the bend so there is some back pressure at the crimp.    But the metal is leaking and tearing up at the crimp so even that amount of back pressure/resistance to flow may not last that much longer.

    The pressure at the riser pipe was reported as something like 400psi over sea level quite a while back (though if you crimped the riser closed it would climb to much higher).
    Now suppose that the crimp (before leaks) increased the pressure to 800psi (over sea level) in the section before the crimp.   If the well head pressure is 6000PSI over sea level, the 800psi back pressure would reduce the flow by 13%.  

    So, yes, the flow will increase some if they cut off the riser.   But by how much?     If they can stop the flow, entirely with the new BOP, it would be worth it.   15,000 barrels per day for three months (1.35 million barrels) or 17,000 barrels per day for a week (0.119 million barrels)?   Stop the flow before hurricane season or after?

    •  I should add (0+ / 0-)

      ... that a 13% increase in flow is a bit more of an issue as long as they are trying to top kill.   If you are only getting 10% of the mud to go down the well casing, 13% additional loss means none goes down the well casing - unless you can pump more down the hole.  So a riser blowout or riser cut off isn't good for top kill.

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