Sunday, August 22, 2010

Pressure Test Promises Hide Monster Well?

National Incident Commander Thad Allen stated the blowout preventer would be replaced out of concern the relief well's final cementing could blow a seal. This raises the question of pressure. How would final cementing put more pressure on the seal than other interventions to date, the top kill, stacking cap, injectivity test or static kill?

Recall success in the well integrity test was 7,500 psi or greater. That same psi is now the seal's breaking point. What would've been a resounding success in well integrity is now the reason to pull the blow out preventer.

Consider Thad Allen's words. On August 2 he said:

We had to pressure-test the Horizon blowout preventer, critical in this process.

There are going to be three different ways we're going to measure pressure, different gauges on the blowout preventer and the riser, and the capping stack itself.

The science team, working with the BP engineers, have decided that as we go through this procedure, that the pressure in the capping stack itself should not exceed 8,000 pounds per square inch.

Allen said on August 9:

Q: Is it possible to release the actual pressure that was obtained during the pressure test? As much data on the pressure to the BOP as we could get would be lovely.

Thad Allen: Yes, I actually had access to those pressure readings. I'm not sure why they can't be released. We will talk to the science team at BP and see if we can get those released later on today.

On August 14 the same reporter followed up on pressure readings:

Q: I understand that you said the 7,500 was the pressure limit on the capping – or the transition spool. Now we know you were going to go to 9,000, expected to go up to 9,000 in integrity test. Was that a differential or a absolute pressure difference, or limit? And also, we have – been reports that the LMRP has a 5,000 psi limit. Is that correct?

Thad Allen: Well, we will get the details and I'll provide you the information based on personal discussions I've had with the BP engineers in Houston, their indication is that the weakest point of the assembly are regarding pressure. Pressure is the – what we call the spooling tool – that was the device that was inserted into the lower marine riser package that allowed it to be able to be hooked up to the capping stack and the threshold there is 7,500 psi.

We had established, as you know, 8,000 psi is the limit for the well integrity test and how we actually bring those pressures up and how we monitor them are actually something to a procedure that is approved for each test. I can go back and give you the variance and whether or not there was a differential, I just don't happen to have the information in front of me right now and we'll provide that to you.

Why the mystery over pressure, when Allen set it as the gauge for success on August 2?

What you want is the pressure to slowly decrease until it becomes zero in the well. That means the amount of mud is equal to the pressure being pushed up. But if it stops somewhere short of that, that means we may have a problem with the integrity of the casing of the wellbore, so we really won't know until we do the final diagnostics. And, again, that will tell us what we need to do for the bottom kill.
Matt Simmons hammered the lack of integrity of the wellbore. Thad admitted as much. While Simmons passed away, a scientist offers a similar assessment:

The geology is fractured.
Bill Clinton called the BP well "a geologic monster."

When it's not expected, monsters attack.

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