Engineer explains the "bottom kill" relief well and more

http://www.abovetopsecret.com/forum/thread576723/pg1

* I don't know this website but have read elsewhere that the chance of the relief well working is only 50%. This engineer, he describes himself as an oil man of 30 years, discusses the difficulties. I'm sure there is more out there on this topic. I think that the masses are going to be mighty disturbed if come August we have no results. But until then the idea is going to be floated that the relief wells are a sure thing.

I think we need to be in the streets and on the phone. BP needs to throw MORE at this, another two relief wells might help. They will not do it until WE ARE IN THE STREETS, imo.


What’s really happening in the Gulf Oil Spill

SNIP

A “bottom kill” is vastly easier and is what the relief wells are about. Unfortunately for that to work the relief well must intersect an 8 ¾” diameter well bore 3 miles underground in the dark. It has been and can be done, but the deep intersection is necessary so that the enormous bottomhole reservoir pressure can be offset with heavy drilling fluid. The drilling mud will then displace the oil and gas from the bottom rather than try to force somewhere it doesn’t want to go. Once the heavy fluid balances the bottomhole pressure then cement can be put into place that once set up will end the need for the heavy fluid.

Do you know anything about plate tectonics, and fault line pressures?

Because that oil was under tremendous pressure, being balanced equally against the landmass above it, and whatnot...


So, if this thing goes TOO far, it may just "Shift" and crack the entire well bore channel....

Although, I will admit that the flow from the riser appears to be within common pumping volumes.

SNIP

* My point is that the relief well is not a sure thing and they will not be honest about the difficulties because then they would have to spend more on back-up solutions. They are a pathetic company, not on our side.

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I'm a drilling engineer for one of the 10 largest onshore natural gas producers in the US so that's my background to answer this question.

There is only one way to actually stop the flow from the formation. That is to pump a heavyweight fluid into the wellbore that will result in a hydrostatic pressure that is higher than the pressure in the formation. Then, they follow the "kill" fluid with cement to permanently seal the wellbore.

This is the ONLY permanent solution. This can be achieved by two methods. The first is a bottom kill which is always the preferred method. The basic rule of well control is to never let the bubble get below you. So have the bit on bottom, shut the well in and circulate kill fluid into the well while using an adjustable choke to maintain a constant bottom hole pressure.

Well right now the traditional bottom kill isn't an option. So what we do is drill a relief well to either actually intersect with the problem well or get within about 20' of the problem well. At this point the kill fluid is pumped into the problem well and as the column of kill fluid rises in the problem well the well will be killed. If the well can only get within about 20' of the problem well then high enough pump pressure is used to breakdown the formation. The fracture will naturally grow towards the problem well because the problem well represents a weak spot in the formation so the stress concentrates around that wellbore. This method does not require a functioning BOP but it does require a competent intact wellhead.

BP is working on this now. Development Driller III spud the first relief well on 3 May and Development Driller II spud the second relief well on 16 May. DDIII has almost reached the point where they will pick up directional tools and begin to drill towards the problem well.

The second method for this is a top kill. This is used when the bubble is below you. It invloves shutting the well in and pumping fluid below the BOP stack that is heavy enough and with sufficient pump pressure that pressure in the wellbore is high enough to overcome the formation pressure. At this point the fluid in the wellbore will begin to go back into formation. You have to walk a fine line where the fluid goes back into the formation but you do not breakdown the formation and induce a fracture. This method requires a means of shutting in the well at surface and a competent intact wellhead.

Almost everytime this method is used the means of shutting the well in is the BOP stack. In this situation it is non-functioning. This is where the junk shot comes into play. Junk shots are a widely used and recognized technique. It operates on the same principle that would happen if you tried to flush a bucket full of piece of string down a toilet. The material starts to clump together and eventually clogs the BOP. Everyone has their own "recipe" for a junk shot. Some people swear by ground up tires, some like copper wire cut into 2"-3" long pieces. Some insist on pumping golfballs first to give the other material something to cling to. But the bottom line is that they do work. Here's the issue here; on land if the ground up tires don't work it's relatively easy to get a different material out there to pump. 5,000' underwater it's a bit more complicated so you have to do a lot of due diligence to make sure you give it the best shot.

You might notice that one thing all of these methods have in common is the need for a competent intact wellhead. If any kind of explosives were used to try to pinch off the flow ther is the serious chance of damaging the wellhead. If the flow were pinched off above the wellhead and the wellhead is damaged the flow will begin to come out of the wellhead. This would make kill operations more complicated. If the flow is stanched below the wellhead. The surface casing string would likely be damaged and it would induce an "underground" blowout. This is where the pressure from the blowout breaks down a weak formation and the formation fluids go into that formation. Sounds good right? Wrong! This would be even worse than the current situation. If the breakdown happens deep then well can never be permanently killed. If it happens shallow (more likely if you damage the wellhead and surface casing) the formation fluid will go into the formation and begin seeping out of the seafloor. Now instead of 5,000 bbls coming from 2 leaks you have 5,000 bbls coming from an uncountable number of leaks. Now containment is impossible and killing the well is next to impossible. Disaster.

BP is not going to do anything that will put the integrity of the wellhead in jeopardy for these reasons. I know it sounds screwy but the operations they are presently undertaking offer the best chance of permanently killing the Macondo 252.

Thanks for posting this one, flamingdem.