Written by fatih al-farahat in


BP Well Technical Details






This is all extremely technical and will not be to most reader’s taste.  However there is some take home information.

 

1                    Apparently the well has failed a few thousands of feet down.  That appears to be the explanation for their actions that otherwise would not make sense at all.

2                    We can anticipate a possible complete well collapse though erosion effects appear overstated here.

3                    This means that the only method is the relief wells themselves and that is two months out.  These wells will or should divert a lot of the available oil and possibly allow the runaway to be somehow dealt with.

4                    The president of BP should be charged with criminal negligence as the apparent behavior spells out.  Inflexible orders to speed up drilling overriding the supervisor’s best judgment are betting the company for nothing except ego.

 

Also all the engineers who signed off on this behavior should also be fired for cause, if only to remind the industry that there are higher obligations than a bosses’ whim that kills.

 

Top BP Blowout News of the Past Few Days


Posted: June 12th, 2010 by: h-1

Here’s another posting that got lost in theOilDrum.com comment thread Deepwater Oil Spill – A Longer Term Problem, Personnel – and Open Thread 2

I’ve corrected a few factual errors, and those corrections will appear in [...] in the quote body, and I’ve also cleaned up the links/quotes to make them more readable. Other than that all content is as it appeared Saturday night. Please note that the original source for this was as far as I can tell on godlikeproductions.com/forum1/ – The BP Deep water horizon, Macondo Well Blowout. and what we are facing in the Gulf Part II

A similar discussion/posting of a casing failure can be found at nakedcapitalism.com – Guest Post: BP Official Admits to Damage BENEATH THE SEA FLOOR, June 12 2010, with relevant quotes and support arguments.


Also please make sure to read the discussion I’ve posted under this main article/posting that looks at some of the key points from a technical perspective.

dougr on June 13, 2010 – 3:17am  OK let’s get real about the GOM oil flow. There doesn’t really seem to be much info on TOD that furthers more complete understanding of what’s really happening in the GOM.

As you have probably seen and maybe feel yourselves, there are several things that do not appear to make sense regarding the actions of attack against the well. Don’t feel bad, there is much that doesn’t make sense even to professionals unless you take into account some important variables that we are not being told about. There seems to me to be a reluctance to face what cannot be termed anything less than grim circumstances in my opinion. There certainly is a reluctance to inform us regular people and all we have really gotten is a few dots here and there…

First of all…set aside all your thoughts of plugging the well and stopping it from blowing out oil using any method from the top down. Plugs, big valves to just shut it off, pinching the pipe closed, installing a new bop or lmrp, shooting any epoxy in it, top kills with mud etc etc etc….forget that, it won’t be happening..it’s done and over. In fact actually opening up the well at the subsea source and allowing it to gush more is not only exactly what has happened, it was probably necessary, or so they think anyway.

So you have to ask WHY? Why make it worse?…there really can only be one answer and that answer does not bode well for all of us. It’s really an inescapable conclusion at this point, unless you want to believe that every Oil and Gas professional involved suddenly just forgot everything they know or woke up one morning and drank a few big cups of stupid and got assigned to directing the response to this catastrophe. Nothing makes sense unless you take this into account, but after you do…you will see the “sense” behind what has happened and what is happening. That conclusion is this:

The well bore structure is compromised “Down hole”.

That is something which is a “Worst nightmare” conclusion to reach. While many have been saying this for some time as with any complex disaster of this proportion many have “said” a lot of things with no real sound reasons or evidence for jumping to such conclusions, well this time it appears that they may have jumped into the right place…

TOP KILL – FAILS:

This was probably our best and only chance to kill this well from the top down. This “kill mud” is a tried and true method of killing wells and usually has a very good chance of success. The depth of this well presented some logistical challenges, but it really should not of presented any functional obstructions. The pumping capacity was there and it would have worked, should have worked, but it didn’t.

It didn’t work, but it did create evidence of what is really happening. First of all the method used in this particular top kill made no sense, did not follow the standard operating procedure used to kill many other wells and in fact for the most part was completely contrary to the procedure which would have given it any real chance of working.

When a well is “Killed” using this method heavy drill fluid “Mud” is pumped at high volume and pressure into a leaking well. The leaks are “behind” the point of access where the mud is fired in, in this case the “choke and Kill lines” which are at the very bottom of the BOP (Blow Out Preventer) 

The heavy fluid gathers in the “behind” portion of the leaking well assembly, while some will leak out, it very quickly overtakes the flow of oil and only the heavier mud will leak out. Once that “solid” flow of mud is established at the leak “behind” the well, the mud pumps increase pressure and begin to overtake the pressure of the oil deposit. The mud is established in a solid column that is driven downward by the now stronger pumps. The heavy mud will create a solid column that is so heavy that the oil deposit can no longer push it up, shut off the pumps…the well is killed…it can no longer flow.

Usually this will happen fairly quickly, in fact for it to work at all…it must happen quickly. There is no “trickle some mud in” because that is not how a top kill works. The flowing oil will just flush out the trickle and a solid column will never be established. Yet what we were told was “It will take days to know whether it worked”….”Top kill might take 48 hours to complete”…the only way it could take days is if BP intended to do some “test fires” to test integrity of the entire system. The actual “kill” can only take hours by nature because it must happen fairly rapidly. It also increases strain on the “behind” portion and in this instance we all know that what remained was fragile at best.

Early that afternoon we saw a massive flow burst out of the riser “plume” area. This was the first test fire of high pressure mud injection. Later on same day we saw a greatly increased flow out of the kink leaks, this was mostly mud at that time as the kill mud is tanish color due to the high amount of Barite which is added to it to weight it and Barite is a white powder.

We later learned the pumping was shut down at midnight, we weren’t told about that until almost 16 hours later, but by then…I’m sure BP had learned the worst. The mud they were pumping in was not only leaking out the “behind” leaks…it was leaking out of someplace forward…and since they were not even near being able to pump mud into the deposit itself, because the well would be dead long before…and the oil was still coming up, there could only be one conclusion…the wells casings were ruptured and it was leaking “down hole”

They tried the “Junk shot”…the “bridging materials” which also failed and likely made things worse in regards to the ruptured well casings.

“Despite successfully pumping a total of over 30,000 barrels of heavy mud, in three attempts at rates of up to 80 barrels a minute, and deploying a wide range of different bridging materials, the operation did not overcome the flow from the well.”

80 Barrels per minute is over 200,000 gallons per hour, over 115,000 barrels per day…did we seen an increase over and above what was already leaking out of 115k bpd?….we did not…it would have been a massive increase in order of multiples and this did not happen.

“The whole purpose is to get the kill mud down,” said Wells. “We’ll have 50,000 barrels of mud on hand to kill this well. It’s far more than necessary, but we always like to have backup.”


Try finding THAT quote around…it’s been scrubbed…here’s a cached copy of a quote…

[Note: it was easy to find a sourced copy of that quote, let's not get carried away with conspiracy thinking when it's not needed:]

“The “top kill” effort, launched Wednesday afternoon by industry and government engineers, had pumped enough drilling fluid to block oil and gas spewing from the well, Allen said. The pressure from the well was very low, he said, but persisting.”

“Allen said one ship that was pumping fluid into the well had run out of the fluid, or “mud,” and that a second ship was on the way. He said he was encouraged by the progress.”


Later we found out that Allen had no idea what was really going on and had been “Unavailable all day”


So what we had was BP running out of 50,000 barrels of mud in a very short period of time. An amount far and above what they deemed necessary to kill the well. Shutting down pumping 16 hours before telling anyone, including the president. We were never really given a clear reason why “Top Kill” failed, just that it couldn’t overcome the well.

There is only one article anywhere that says anything else about it at this time of writing…and it’s a relatively obscure article from the wall street journal “online” citing an unnamed source.

“WASHINGTON—BP PLC has concluded that its “top-kill” attempt last week to seal its broken well in the Gulf of Mexico may have failed due to a malfunctioning disk inside the well about 1,000 feet below the ocean floor.

The disk, part of the subsea safety infrastructure, may have ruptured during the surge of oil and gas up the well on April 20 that led to the explosion aboard the Deepwater Horizon rig, BP officials said.

The rig sank two days later, triggering a leak that has since become the worst in U.S. history.

The broken disk may have prevented the heavy drilling mud injected into the well last week from getting far enough down the well to overcome the pressure from the escaping oil and gas, people familiar with BP’s findings said. They said much of the drilling mud may also have escaped from the well into the rock formation outside the wellbore.

As a result, BP wasn’t able to get sufficient pressure to keep the oil and gas at bay. If they had been able to build up sufficient pressure, the company had hoped to pump in cement and seal off the well. The effort was deemed a failure on Saturday.

BP started the top-kill effort Wednesday afternoon, shooting heavy drilling fluids into the broken valve known as a blowout preventer. The mud was driven by a 30,000 horsepower pump installed on a ship at the surface. But it was clear from the start that a lot of the “kill mud” was leaking out instead of going down into the well.”


There are some inconsistencies with this article.

There are no “Disks” or “Subsea safety structure” 1,000 feet below the sea floor, all that is there is well bore. There is nothing that can allow the mud or oil to “escape” into the rock formation outside the well bore except the well, because it is the only thing there.

All the actions and few tid bits of information all lead to one inescapable conclusion. The well pipes below the sea floor are broken and leaking. Now you have some real data of how BP’s actions are evidence of that, as well as some murky statement from “BP officials” confirming the same.

I took some time to go into a bit of detail concerning the failure of Top Kill because this was a significant event. To those of us outside the real inside loop, yet still fairly knowledgeable, it was a major confirmation of what many feared. That the system below the sea floor has serious failures of varying magnitude in the complicated chain, and it is breaking down and it will continue to.

What does this mean?

It means they will never cap the gusher after the wellhead. They cannot…the more they try and restrict the oil gushing out the bop?…the more it will transfer to the leaks below. Just like a leaky garden hose with a nozzle on it. When you open up the nozzle?…it doesn’t leak so bad, you close the nozzle?…it leaks real bad, same dynamics. It is why they sawed the riser off…or tried to anyway…but they clipped it off, to relieve pressure on the leaks “down hole”. I’m sure there was a bit of panic time after they crimp/pinched off the large riser pipe and the Diamond wire saw got stuck and failed…because that crimp diverted pressure and flow to the rupture down below.

Contrary to what most of us would think as logical to stop the oil mess, actually opening up the gushing well and making it gush more became direction BP took after confirming that there was a leak. In fact if you note their actions, that should become clear. They have shifted from stopping or restricting the gusher to opening it up and catching it. This only makes sense if they want to relieve pressure at the leak hidden down below the seabed…..and that sort of leak is one of the most dangerous and potentially damaging kind of leak there could be. It is also inaccessible which compounds our problems. There is no way to stop that leak from above, all they can do is relieve the pressure on it and the only way to do that right now is to open up the nozzle above and gush more oil into the gulf and hopefully catch it, which they have done, they just neglected to tell us why, gee thanks.

A down hole leak is dangerous and damaging for several reasons.

There will be erosion throughout the entire beat up, beat on and beat down remainder of the “system” including that inaccessible leak. The same erosion I spoke about in the first post is still present and has never stopped, cannot be stopped, is impossible to stop and will always be present in and acting on anything that is left which has crude oil “Product” rushing through it. There are abrasives still present, swirling flow will create hot spots of wear and this erosion is relentless and will always be present until eventually it wears away enough material to break it’s way out. It will slowly eat the bop away especially at the now pinched off riser head and it will flow more and more. Perhaps BP can outrun or keep up with that out flow with various suckage methods for a period of time, but eventually the well will win that race, just how long that race will be?…no one really knows….However now?…there are other problems that a down hole leak will and must produce that will compound this already bad situation.

This down hole leak will undermine the foundation of the seabed in and around the well area. It also weakens the only thing holding up the massive Blow Out Preventer’s immense bulk of 450 tons. In fact?…we are beginning to the results of the well’s total integrity beginning to fail due to the undermining being caused by the leaking well bore.

The first layer of the sea floor in the gulf is mostly lose material of sand and silt. It doesn’t hold up anything and isn’t meant to, what holds the entire subsea system of the Bop in place is the well itself.

 The very large steel connectors of the initial well head “spud” stabbed in to the sea floor. The Bop literally sits on top of the pipe and never touches the sea bed, it wouldn’t do anything in way of support if it did. After several tens of feet the seabed does begin to support the well connection laterally (side to side) you couldn’t put a 450 ton piece of machinery on top of a 100′ tall pipe “in the air” and subject it to the side loads caused by the ocean currents and expect it not to bend over…unless that pipe was very much larger than the machine itself, which you all can see it is not. The well’s piping in comparison is actually very much smaller than the Blow Out Preventer and strong as it may be, it relies on some support from the seabed to function and not literally fall over…and it is now showing signs of doing just that….falling over.

If you have been watching the live feed cams you may have noticed that some of the ROVs are using an inclinometer…and inclinometer is an instrument that measures “Incline” or tilt. The BOP is not supposed to be tilting…and after the riser clip off operation it has begun to…

This is not the only problem that occurs due to erosion of the outer area of the well casings. The way a well casing assembly functions it that it is an assembly of different sized “tubes” that decrease in size as they go down. These tubes have a connection to each other that is not unlike a click or snap together locking action. After a certain length is assembled they are cemented around the ouside to the earth that the more rough drill hole is bored through in the well making process. A very well put together and simply explained process of “How to drill a deep water oil well” is available here:


The well bore casings rely on the support that is created by the cementing phase of well construction. Just like if you have many hands holding a pipe up you could put some weight on the top and the many hands could hold the pipe and the weight on top easily…but if there were no hands gripping and holding the pipe?…all the weight must be held up by the pipe alone. The series of connections between the sections of casings are not designed to hold up the immense weight of the BOP without all the “hands” that the cementing provides and they will eventually buckle and fail when stressed beyond their design limits.

These are clear and present dangers to the battered subsea safety structure (bop and lmrp) which is the only loose cork on this well we have left. The immediate (first 1,000 feet) of well structure that remains is now also undoubtedly compromised. However…..as bad as that is?…it is far from the only possible problems with this very problematic well. There were ongoing troubles with the entire process during the drilling of this well. There were also many comprises made by BP IMO which may have resulted in an overall weakened structure of the entire well system all the way to the bottom plug which is over 12,000 feet deep. Problems with the cementing procedure which was done by Haliburton and was deemed as “was against our best practices.” by a Haliburton employee on April 1st weeks before the well blew out. There is much more and I won’t go into detail right now concerning the lower end of the well and the troubles encountered during the whole creation of this well and earlier “Well control” situations that were revealed in various internal BP e-mails. I will add several links to those documents and quotes from them below and for now, address the issues concerning the upper portion of the well and the region of the sea floor.

What is likely to happen now?

Well…none of what is likely to happen is good, in fact…it’s about as bad as it gets. I am convinced the erosion and compromising of the entire system is accelerating and attacking more key structural areas of the well, the blow out preventer and surrounding strata holding it all up and together. This is evidenced by the tilt of the blow out preventer and the erosion which has exposed the well head connection. What eventually will happen is that the blow out preventer will literally tip over if they do not run supports to it as the currents push on it. I suspect they will run those supports as cables tied to anchors very soon, if they don’t, they are inviting disaster that much sooner.

Eventually even that will be futile as the well casings cannot support the weight of the massive system above with out the cement bond to the earth and that bond is being eroded away. When enough is eroded away the casings will buckle and the BOP will collapse the well. If and when you begin to see oil and gas coming up around the well area from under the BOP? or the area around the well head connection and casing sinking more and more rapidly? …it won’t be too long after that the entire system fails. BP must be aware of this, they are mapping the sea floor sonically and that is not a mere exercise. Our Gov’t must be well aware too, they just are not telling us.

All of these things lead to only one place, a fully wide open well bore directly to the oil deposit…after that, it goes into the realm of “the worst things you can think of” The well may come completely apart as the inner liners fail. There is still a very long drill string in the well, that could literally come flying out…as I said…all the worst things you can think of are a possibility, but the very least damaging outcome as bad as it is, is that we are stuck with a wide open gusher blowing out 150,000 barrels a day of raw oil or more. There isn’t any “cap dome” or any other suck fixer device on earth that exists or could be built that will stop it from gushing out and doing more and more damage to the gulf. While at the same time also doing more damage to the well, making the chance of halting it with a kill from the bottom up less and less likely to work, which as it stands now?….is the only real chance we have left to stop it all.
It’s a race now…a race to drill the relief wells and take our last chance at killing this monster before the whole weakened, wore out, blown out, leaking and failing system gives up it’s last gasp in a horrific crescendo.

We are not even 2 months into it, barely half way by even optimistic estimates. The damage done by the leaked oil now is virtually immeasurable already and it will not get better, it can only get worse. No matter how much they can collect, there will still be thousands and thousands of gallons leaking out every minute, every hour of every day. We have 2 months left before the relief wells are even near in position and set up to take a kill shot and that is being optimistic as I said.

Over the next 2 months the mechanical situation also cannot improve, it can only get worse, getting better is an impossibility. While they may make some gains on collecting the leaked oil, the structural situation cannot heal itself. It will continue to erode and flow out more oil and eventually the inevitable collapse which cannot be stopped will happen. It is only a simple matter of who can “get there first”…us or the well.

We can only hope the race against that eventuality is one we can win, but my assessment I am sad to say is that we will not.

The system will collapse or fail substantially before we reach the finish line ahead of the well and the worst is yet to come.

Sorry to bring you that news, I know it is grim, but that is the way I see it….I sincerely hope I am wrong.

We need to prepare for the possibility of this blow out sending more oil into the gulf per week then what we already have now, because that is what a collapse of the system will cause. All the collection efforts that have captured oil will be erased in short order. The magnitude of this disaster will increase exponentially by the time we can do anything to halt it and our odds of actually even being able to halt it will go down.

The magnitude and impact of this disaster will eclipse anything we have known in our life times if the worst or even near worst happens…

We are seeing the puny forces of man vs the awesome forces of nature.

We are going to need some luck and a lot of effort to win… and if nature decides we ought to lose, we will….




Reference materials:

On April 1, a job log written by a Halliburton employee, Marvin Volek, warns that BP’s use of cement “was against our best practices.”

An April 18 internal Halliburton memorandum indicates that Halliburton again warned BP about its practices, this time saying that a “severe” gas flow problem would occur if the casings were not centered more carefully.

Around that same time, a BP document shows, company officials chose a type of casing with a greater risk of collapsing.


Mark Hafle, the BP drilling engineer who wrote plans for well casings and cement seals on the Deepwater Horizon’s well, testified that the well had lost thousands of barrels of mud at the bottom.

 But he said models run onshore showed alterations to the cement program would resolve the issues, and when asked if a cement failure allowed the well to “flow” gas and oil, he wouldn’t capitulate.

Hafle said he made several changes to casing designs in the last few days before the well blew, including the addition of the two casing liners that weren’t part of the original well design because of problems where the earthen sides of the well were “ballooning.” He also worked with Halliburton engineers to design a plan for sealing the well casings with cement.



Casing joint

Kill may take until Christmas

BP Used Riskier Method to Seal Well Before Blast

BP memo test results

Investigation results
The information from BP identifies several new warning signs of problems. According to BP there were three flow indicators from the well before the explosion.


BP, what we know

What could have happened
1. Before or during the cement job, an influx of hydrocarbon enters the wellbore.

2. Influx is circulated during cement job to wellhead and BOP.

3. 9-7/8” casing hanger packoff set and positively tested to 6500 psi.

4. After 16.5 hours waiting on cement, a negative test performed on wellbore below BOP. (~ 1400 psi differential pressure on 9-7/8” casing hanger packoff and ~ 2350 psi on double valve float collar)

5. Packoff leaks allowing hydrocarbon to enter wellbore below BOP. 1400 psi shut in pressure observed on drill pipe (no flow or pressure observed on kill line)

6. Hydrocarbon below BOP is unknowingly circulated to surface while finishing displacing the riser.

7. As hydrocarbon rises to surface, gas break out of solution further reduces hydrostatic pressure in well. Well begin to flow, BOPs and Emergency Disconnect System (EDS) activated but failed.

8. Packoff continues to leak allowing further influx from bottom.

Confidential. BP. What Could Have Happened


T/A daily log 4-20

Cement plug 12,150 ft SCMT logging tool
SCMT (Slim Cement Mapping Tool)
Schlumberger Partial CBL done.

Schlum CBL tools

Major concerns, well control, bop test.

Energy & commerce links to docs.                              energycommerce.house.gov
well head on sea floor                                                 nca-group.com – jpg image
Well head on deck of ship                                            nca-group.com – jpg image

BP’s youtube propoganda page, a lot of rarely seen vids here….FWIW


[Note: This appears to be the source of the original posting, which suggests dougr took it from there, or is SHR himself.

I used to cover the energy business (oil, gas and alternative) here in Texas, and the few experts in the oil field -- including geologists, chemists, etc. -- able or willing to even speak of this BP event told me early on that it is likely the entire reserve will bleed out. Unfortunately none of them could say with any certainty just how much oil is in the reserve in question because, for one thing, the oil industry and secrecy have always been synonymous. According to BP data from about five years ago, there are four separate reservoirs containing a total of 2.5 billion barrels (barrels not gallons). One of the reservoirs has 1.5 billion barrels. I saw an earlier post here quoting an Anadarko Petroleum report which set the total amount at 2.3 billion barrels. One New York Times article put it at 2 billion barrels.
If the BP data correctly or honestly identified four separate reservoirs then a bleed-out might gush less than 2 to 2.5 billion barrels unless the walls -- as it were -- fracture or partially collapse. I am hearing the same dark rumors which suggest fracturing and a complete bleed-out are already underway. Rumors also suggest a massive collapse of the Gulf floor itself is in the making. They are just rumors but it is time for geologists or related experts to end their deafening silence and speak to these possibilities.

All oilmen lie about everything. The stories one hears about the extent to which they will protect themselves are all understatements. BP employees are already taking The Fifth before grand juries, and attorneys are laying a path for company executives to make a run for it.

Because of the length of the above posting, I'm including the license terms of this posting.

All content at theOilDrum.com is released under the Creative Commons License


Further Discussion on Technical Components of this Question at theOilDrum.com


The next day there were some relevant comments, I'll list them here for now as they appeared in theOilDrum.com - BP's Deepwater Oil Spill - the Problem of Cleaning Up Marshes - and Open Thread thread.

R2-3D on June 13, 2010 - 12:48pm Permalink | Subthread | Parent | Parent subthread | Comments top

Yes, with any blowout, you have the possibility of a parted casing string(s) downhole. Underground blowouts with burst casing are often related to shallow sands. After the well is controlled, you can run shallow (hi-resolution) seismic surveys (a series of single 2D lines at first) that will tell you where your subsurface hydrocarbons went. I've mentioned before I once sat on a relief well for an offshore blowout. The BOP stack was shut in (but it partially failed) but was shut in enough to cause the well to have a subsurface blowout. The gas flowed out the burst casing and along the outside of the whole thing and up to the surface. It also charged (flowed into) a shallow gas sand at about the same level as the burst casing. It was estimated later perhaps 3Bcfg flowed into the shallow sand in the vicinity of the blowout well. The blowout well "bridged over" before long. It most likely bridged over closest to the surface, as the gas quit flowing to the surface after a day or so, but since the shallow sand took maybe 3Bcf, the gas probably continued to flow into the shallow sand from the formations, up inside the casing and then through two strings of casing into the shallow sand.

Did the Top Kill give any information about a possible casing breach?

I'm pretty much out of my league when I talk about engineering casing designs; grab those salt grains as you read further.  With this Macondo 252 #1-01:

You have 36" conductor(drive) pipe set to 320+ ft below mudline. Traditionally, these are driven down, banged on (it's loud) until you can't bang on them any more.

Next you have the 28" casing (surface pipe) that is set in this case to around 1200' +/- below mudline.

You then have the 22" casing that is set about 2900' +/- below mudline. I believe this is the pipe that most likely supports the bulk of the weight of the BOP stack.

The 18" is a liner that's hung off of the 22" stack, I think. The base of the 18" is nearly 4000' below mudline. I don't know where the top of the 18" liner casing is, but let's say 250' above the base of the casing it was hung on, or about 2700' below mudline.

Then the 16" is run to the base of the BOP stack. The base of the 16" is 6860' below mudline.

If the formation fluids are coming up the outside of the 7 x 9 5/8" tapered casing, they're going up the inside of the 16" casing.

So, let's say that the fluids coming up the annulus between the 7 x 9 5/8" tapered casing and the 16" casing, and there's somehow enough backpressure to burst through the casing. Let's say it's going through the 16" casing. Most likely, it would not go through the 22" AND the 28" casing, but perhaps choose a spot lower than the base of the 28" casing. (Why not go out deeper? It could. But bear with me) I seriously doubt it went out through the 16, 22, 28 and the 36 inch casing strings all at once within a few hundred feet of the surface.

So, I'm painting a scenario where the oil and gas "choose" a window to burst through. This assumes there's enough backpressure to create that burst level pressure downhole. After all, if that "burst window" was that easy to pop through in the first place, the blowout would never have made it to the surface. Perhaps the riser keeling over created some temporary kinks before the riser kink itself breached. Who knows?

This all _assumes_ there _is_ a casing breach, something that's merely speculated on. I'm trying to get to this description to make my own point.

What I'm suggesting is that _if_ there is a casing breach, it's through the 16" and the 22" casing somewhere between 2700' below mudline (or above whereever the 18" liner is hanged from) and 1200' below mudline (the base of the 28" casing shoe) [Note: my emphasis]

If there’s anyone that asks you, “Why do they run electric logs all the way to the surface, you have a reason to tell them. Don’t you want to know if there are any sandy sections in that interval? I know I do.

Okay, we have a theoretical breach of two strings of casing between 2700′ below mudline and 1200′ below mudline in this scenario. Did the formation fluid get far, or did it seek the path of least resistance and travel up the outside of the casing/cement to the base of the BOP stack? Well, we might see blips and blobs of oil/gas or we might see a torrent.

NOW, let’s talk about the Top Kill. You have the BP engineers that already know what I’ve said to you. It’s a possibility. You deal with the reality. The reality is the bulk of the oil is coming up the BOP and into the riser. The Top Kill is tried after the new control pod is placed on the BOP stack. Pressures within the BOP stack are taken at various points before and after the Top Kill. I suspect the flow rates of mud and the pressures didn’t exactly match up, but that’s speculation on my part. What the effect of the Top Kill is, is to increase pressure at the surface, “bullheading” the formation fluids back down. The mud is pumped with enough volume to overcome the riser leaks. If you do this slowly, you don’t run a high risk of _causing_ a subsurface blowout, but if there is one already there, you could open that up and leak off into the shallow sands.

So, let’s say that some pressures and pumping mud volumes gave some BP engineers some indication that they’ve got a breach in the casing. They stop the Top Kill and proceed with capturing the oil as best they can (not so well so far, but whatever) in a passive manner.

Now to my point (whew, that was a long way to get here!)

The casing design means there’s little chance of the BOP stack falling over, or even moving five inches from its spot.

It also means there’s little chance for the BOP stack to fall off or completely break. What exactly is bent and at what angles are of interest. Did something bend enough below the BOP stack to break, and are we in danger of fluids coming out of somewhere really shallow? We don’t know. If fluids come out of a very shallow breach due to bending stresses, does that mean the well has failed? Far from it. The erosion you hear about is overrated. Formation sands can be made to erode, but there’s got to be a lot of them. Do you see that sand floating down in huge volumes? We saw the bullseye level the other day and that was not covered in all that much sand. We should see huge volumes of sand coating every bit of the BOP’s lower sections. We don’t. Sand production isn’t a big issue in this case at the moment. [Note: my emphasis]

Do any fluids going into our theoretical casing breach mean anything? Well, they’re obviously not coming up around the BOP stack in large volumes. Is the oil and gas leaving our breach and traveling laterally? Perhaps. What’s the mechanism? Have the fluids traveled seven miles away and only then popped up to the mudline to leak away? Now you have to calculate some volumes. What’s 7 miles times say 1800 feet wide times 20 feet high? Fill that volume with 5 ft of net oil, so instead of 20 feet high, it’s only 5 effective feet of oil ‘tall’. Maybe 3,000,000 barrels. Hey, anything is possible.

Point is, if the oil and gas DID leak through a casing breach, it’s meaningless to both the oil spill killing shore critters and relief wells.

Why does a casing breach not impact a relief well operation? Can’t the control mud flowing up the blowout from the relief well intersection just flow into the shallow formation forever, UTubing and preventing control of the blowout downhole? In theory, yes.

This is where the control fluids are added to the heavy mud, and this time it’s more than cellophane and nutshells. All you have to worry about is the top of the BOP stack. There needs to be some pushback ready to go. Those orifices are too big to control, but the theoretical casing breach 1800′ below the mudline is a problem, but it’s not an insurmountable problem.

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cudBwrong on June 13, 2010 – 3:45pm Permalink | Subthread | Parent | Parent subthread | Comments top
R2: thanks for this detailed description.
The potential consequences of a casing breech depend upon the detailed circumstances.

One way to think about it is to imagine drilling a well from the bottom up. Suppose you had a rig down inside the reservoir, and you are drilling up towards the surface.

All of the material above the reservoir, the formations of rock, sand, sediment, and the seawater column, act like a huge column of drilling mud: they work to hold the reservoir in place.

If you drill up one foot, nothing is going to happen. The remaining materials will continue to hold the reservoir, as they have done for geologic periods of time.

If you drill all the way up to within a few feet of the sea floor, well, things might get interesting. The remaining overburden could give way, giving the reservoir a means of escaping into the water.
So the consequences very much depend upon the geology and pressures at and around the breech location

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R2-3D on June 13, 2010 – 4:56pm Permalink | Subthread | Parent | Parent subthread | Comments top
The Overshot Tool will be turned upside down over the entire area where the LMRP cap is now. Somehow, there will be a seal or two, or the entire thing will be lined with neoprene along the sides.

 How this seal functions we aren’t told, but we have been told they (BP engineers) expect to not worry about the seawater incursion. This means at least a decent seal, but probably a low leak off (this number will be critical, and it’s it’s not 1000# someone hasn’t designed this properly). (Again, I’m not an engineer, but part of the peanut gallery)

When the mud comes up from the relief well bottom kill, it will easily go past the BOP at the mudline and either

a)      travel up the riser or whatever conducts the oil to the surface after the Overshot Tool is in place
or
b) the valve at the Overshot Tool connection will be closed.

This is that “backpressure” you have to have. How good the seal is between the Overshot Tool will be known that day. If there’s a small or no flow, all is working. What lost circulation material is used to seal any casing breach will also work in the seal at the Overshot Tool (however, I suspect that seal will be a dynamic one, and the effect of lost circulation material there will be fleeting.

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