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BP Relief Wells-What Is A Relief Well and How Does It Work?

What Is A Relief Well and How Does It Work?


I have started this discussion  because it has become clear that many people have some misconceptions about what a relief well actually is and does. This became very apparent here when a gentleman with a PhD. wrote a letter to the President of the United States declaring that "BP was lying to us" and that his science showed that a well drilled into this blowout well would never relieve the pressure from this well.

 

I had to delete the post because it was so fundamentally wrong and misleading to readers and damaged the credibility of the Drilling Ahead site. I hope those of you with greater knowledge will help me here with your responses  to explain in simple language what a relief well is and does.

 

First-and most importantly

 

A relief well is not drilled to "relieve pressure and reduce flow of oil",

 

This seems to be the most common misconception. The sole purpose of a relief well is to kill the well completely. To accomplish this the relief well has to drill directly into the 7" casing of the blowout well at a depth of 18,000'. When this happens, a 'window" is cut into the 7" casing of the blowout well and heavy mud is forced into its wellbore. The heavy mud is calculated to counteract the force of the flow in the blowout well, In this case it should be between 14.4 ppg and 15 ppg.

 

When the flowing blowout is filled with this heavy mud the flow will stop completely and the well will become static.At this point you could completely remove the Blowout Preventers if you wanted to and you would see a pipe in the ocean floor full of drilling mud and NOTHING escaping the well.

 

 This is when the well is back in control.

 

 With this accomplished, cement from the relief well platform will be circulated into the blowout well.

 

 With the cement hardened the well will be completely and permanently sealed and abandoned.

 

The relief well is in no way meant to "just relieve pressure on the blowout well to reduce flow

 

The relief well is a permanent solution and will be successful.

 

Only 1 successful relief well is needed to completely seal  this blowout.

 

 The entire purpose of the second relief well is as a backup in the event of problems possibly encountered while drilling the original relief well. The drill string could become stuck-the drill bit could come apart-the possibilities are endless as to things that could go wrong with drilling any well, and fixing these problems could add months to the well-so a second relief well is drilled 'just in case" problems are encountered with the original relief well

 

Here is a short animation that shows a simple understanding of a relief well-what you see at the end of the video is cementing being pumped into the well

 

 

How A Relief Well Actually Works

 

 The relief well begins drilling from a safe distance form the flowing well, in this case 1/2 mile. Then the  relief well is drilled down to about 1000' above the bottom of the flowing well (the blow out) In this case somewhere around 17,000'. Special tools are then run in the hole of the relief well using wireline  that are able to sense the magnetic field of the 7" casing of the blow out well. This tells the people drilling the relief well exactly where the 7" casing is and they drill directly towards it. Several more of these wirelines are run as the new well gets closer and closer to the 7" casing to pinpoint it exactly. The relief well will be successful.

 

Here is a short video that explains how that wireline tool works.


Find more videos like this on Drilling Ahead

 

Here is a more detailed video explaining the relief well

 

 

Another misconception that we are hearing from novices is that a relief well may not be possible or effective. Nothing could be further from the truth. Relief wells have been drilled for over 30 years that I know of, possibly even longer. They were drilled then without the advanced technology we have today and were still completed successfully.

 

 Relief wells are not experimental solutions like the "Top Hat" or the "Junk Shot".

 

Relief wells are drilled every year somewhere on land or offshore to extinguish blowouts and are the accepted proven solution throughout the industry. It will be successful and it will be permanent.

Almost 30 years ago a well that was completed and producing had a blowout caused by the casing parting at over 1000' deep. This well was 30 miles from my home and involved tremendous pressures. As you can see from the photo posted below a canyon was dug all the way down to the parted casing over 1000' deep. At the same time a relief well was started from 1/4 mile away and was drilled down over 17,000' to intersect and kill the well. This was successful and accomplished then without the aid of the advanced technology we have today. It was amazing to watch and to read about in a publication then called "Drilling World". These people using very new and now primitive technology were able to find and drill into a 6" liner at these depths almost 30 years ago-then successfully kill the well with heavy mud.

 


Blowout near Allison Texas Almost 30 Years Ago

 

The Relief Well In The Distance

 

I hope this helps some of you outside the oil and gas industry understand the basics of a relief well. You can rest assured that when this relief well is completed it will be all over except for the clean up.

Tags: BP, blowout, deepwater, horizon, how, it, relief, transocean, well, works

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Replies to This Discussion

I have not seen evidence that the flow is up the 7" X 9-7/8" long string. Could it not be up the annulus of the 7" X 9-7/8" by 16" casing set at 11,585 feet (RKB measurements) which was the last "longstring" cemented? There is a 135 foot section of open hole between the TOC of the 7" and the bottom of the most recently run liner (9-7/8" liner shoe at 17,168 RKB). If this is the case, flow could be up the annulus and cutting into the 7" would not be needed if the bit can be oriented into this 135 foot section for the kill.
While working for Shell Oil Company for 39 years I never worked on an offshore rig. Just a lot of good engineering experience onshore.
BK
Hi Bill,
I just emailed BP on behalf of the website asking for this additional information. I hope they will respond (would be suprised if they did). if I receive the information I will post it here.
Curtis,
In this video BP identifies John Wright (in a Boots & Coots shirt) as the Leader of the Intersection Team. Maybe Boots & Coots would have more information on the strategy for the relief wells. In the video, John makes note of the fact that he has run successful kill operations on 40 wells so far and he does not intend to miss on this one.
Bob
I have to think that BP believes they can kill the well at the 7" otherwise I would think they would be planning on intersecting at the 16" shoe.
I have also said in the past that the Stand Pipe Pressure reached 5800 psi at the time of explosion(according to Halliburton Rig Monitor charts)-to me this would indicate flow also up the 7"X9 7/8s as well as up the drill pipe.
We have also been discussing for sometime that the flow is on the backside of the 7X 9 7/8s. it will be interesting to see how this plays out.
Perhaps "relief well" is an unfortunate naming convention, maybe we should call them "kill wells".

Just a bit of minor input to address this specific statements
"To accomplish this the relief well has to drill directly into the 7" casing of the blowout well at a depth of 18,000'. When this happens, a 'window" is cut into the 7" casing of the blowout well ..."

The relief (or kill) well will be drilled to close proximity of the blowout well and then directionally steered to be parallel to the blowout well for some length, keeping the distance between the well bores to a relative minimum. This will be accomplished with the magnetic ranging tools as outlined above and with the directional tools that are in existence today (the granularity of directional control is quite impressive). After some vertical parallel distance is drilled, windows (multiple) will be cut into the 7" casing or where necessary in order to effect the kill operations.
Thanks Tony,
so you are saying that the relief well will run perpendicular to this well for a good length, then whipstocks will be set from the bottom up to cut windows in several places?
Seems entirely possible and could explain how they will kill/cement both the 16" and the 7 X 9 7/8"

Please let me know if I understand you correctly
vertically parallel (alongside), not perpendicular (just to avoid any confusion).
And yes, multiple cuts into the blowout bore (whipstock or otherwise).
Thanks Tony-my mistake- I did mean parallel. I appreciate your information. Would these cuts extend up the well above the 16" shoe?
Perhaps a successful "relief well" provides a relief of anxiety?!
Curtis, as far as KMW, it would seem to me it is going to take something heavier than 14.4-15.0 ppg as the MW when it blew out was 16.0 ppg. Just my arm chair observation.
Thanks Eddie..that 16 ppg is what the rig recorder showed because it was the mud wt of the last slug pumped(what I am told).
My understanding is the hole was static with 14.2 ppg mud wt prior to the blowout and the junk shot was attempted with 15ppg so I have used that range
This video is probably too basic for most, but it does provide some information on the strategy for the relief well.

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