Reply #7: From the Oildrum site

[csziggy]

Commentary:

gavacho on May 26, 2010 - 8:13pm
If as it appears we are seeing only mud escaping, this means that the top kill is achieving at least a "stand still" with the well. The pressure of the mud is keeping the oil in the hole, and hopefully making headway in forcing mud down the hole. Success will be achieved if the mud gets far enough down the hole so that the pressure exerted by the weight of the coulumn of mud is equal to the pressure of the well. The scary part is that the leaks that the mud is escaping from appear to be enlarging. This is a bad thing, because the more mud that escapes, the harder it is to achieve the pressure necessary to force mud down the hole.


<-> ptone on May 26, 2010 - 8:20pm
I was just thinking the same thing about the race to make use of the available pressure. I don't know if they had extra pressure capacity before the start of the operation. ie if they only need 3000psi to force oil down, but can do 5000psi - do they start at 3K and then only ramp up if the leaks are scoured out bigger - or do you throw your full might at it to get it killed as fast as possible.

<-> codesuidae on May 26, 2010 - 8:57pm
Maybe it depends on how the pressure affects the erosion rate.

If your example of 3000 psi is sufficient to push mud down the hole, it doesn't matter how big the leaks are as long as you can pump sufficient volume to maintain 3000 psi. Bigger holes just mean you have to increase the mud volume.

Increasing the pressure might fill the well faster, but it might also increase the rate of erosion at the leaks. If pumping at lower pressure means that it takes longer but keeps the required volume within available capacity, then you'd keep the pressure down. Also, it seems you wouldn't want to use more pressure than you need to get mud down the well. Mud is cheap, harmless and plentiful, but extra pressure could break something else and make the problem worse.

Worst case, they can keep pumping mud for the next two months until the relief wells are done. How long can you run those big pumps before they wear out?

<-> striker754 on May 26, 2010 - 8:23pm
What mud weight were they using while drilling and what mud weight are they using for kill fluid?

<-> Fracker on May 26, 2010 - 8:32pm
At the end of drilling they were reported to be at 14.4 ppg mud wt. Heard the kill fluid is 16 ppg.
As they are sucessful in pumping the mud downhole, the extra wt of the mud column will subtract from the pressure, and the pressure will decrease. I wish we could see a live plot of injection pressure.

Heading Out on May 26, 2010 - 8:30pm
Ah, in the Press Conference Doug Suttles said that they are only injecting mud at the rate of 20 barrels a minute. (7,000 barrels over 6 hours). This is less than half the anticipated flow (50 barrels) and they may have dropped the injection flow rate to keep pressures in the BOP at an acceptable level. That does increase the time it will take to fill the well significantly (by several hours, depending on the leak rate). Though it also shows that those estimates that the well was leaking at 100,000 barrels a day were fantasy.

It would take 87.5% of the mud injected being lost to leaks, for it to take 22 hours to fill the well, and that would indicate that the leakage rate was 25,000 bd.

http://www.theoildrum.com/node/6511#comment-630110

Plenty of good info there as experts watch the live feed.