This is getting hairy.....there are 2 relief wells, drilled very close in proximity to a damaged horizontally drilled wellbore. There are 2 wellbores that were drilled initially for the production. One had a collapse on to the drill bit, and was cemented and abandoned, one was the "successful" well. They are in close proximaty to each other. Then there is the possibility of leaking and drifting gas and fluids from the shut-in well.
There is the problem of "communication" in between the wellbores, both the original bores, and the relief well bores. It depends on what kind of plug and fluids were left in the first failed bore, and the geological features in the area, and it's proximity to the second bore. If there are any "gas cut " fluids in the failed bore, or any sections where the cement has spaced due to improper gas ratios, in the first bore, then there is the possibility of problems from that.
Then there is the possibility of pressure " communication from the relief well to the wild well. If the pressure in the relief well is not high enough, then there will be a "communication " between the bores, in the direction of the relief well.. The higher pressure from the wild well can blow out the distance between the two bores easily if there is a fluctuation in pressure from the reservoir itself while they are getting close to milling into the outer casing. If the pressure and mud weight are too great, than they will communicate, possibly into the wild wellbore and frac' the reservoir,...again...... producing a massive amount of kick and accompanying gas, which in itself would raise the amount of gas-lift provided to the fluid in the wild bore....thus raising overall pressures., which could in turn cause a simultaneous blowout in between other bores in the area, depending on several factors.
So they could possibly cause a blowout into the releif well/s.
I understand they are going to use a 13ppg mud weight, water-based, for the initial "bull-heading effort" through the new "cap".
I this following MMS document, I found a PDF, describing a very similar scenario , in which there was a previous wellbore that had failed, as had the casing and concrete, and the outer areas outside the wellbore had started to erode under high pressure oil and gas flow. This two phrases caught my eye particularly.
" These wells have the potential of an uncontrolled release of hydrocarbons to the environment."
" It is concluded that the subsidence of Platform “A” may have resulted in casing/tubular buckling for Wells A-1/A-1D, A-2/A-2D and A-3/A-3D. "
http://www.gomr.mms.gov/PDFs/2008/2008-053.pdf
It was describing the underground blowout and subsequent uncontrollable erosions outside a damaged bore.
...so...now, lets think about what has happened since they shut the well in.
Many people have noticed massive clouds and eruptions that seem to happening around the ROV's
That is a valid observation, however you cannot disregard the possibility of a sub-floor blowout around the BOP...it is damaged at the mudline/bedrock...otherwise it wouldn't have been at a 15° lean. Although the interior casing sections may be only bent, the normally tight-fitting connection points comprised of the " shoe " may also have been pulled out of alignment past or above the point of stress. Creep under mudline, the " gas saturation zone " is normal in the event of shutting in a well. How much gas can it hold before it blows out, we may be seeing the start of it....or we may be seeing just silt being kicked up by ROV's....or would could be seeing silt being kicked up by the ROV's on purpose to obscure the venting incidents.....so I would not rule this out as being a " done deal " yet....if they have damaged the area from leaving it shut-in for too long, they may have created a situation in which they cannot proceed with the " static top kill ", although I also understand they are not going to proceed with the operation under extreme pumping pressures, as to not cause any further damage.
Some things to think about.
A. The 2006 February quake originating in the area of the Horizon blowout, a little SE of it, actually.
" The seismograms are fit well by a model of sliding on a shallow, sub-horizontal surface within the thick layer of low-velocity sediments that blankets the Gulf of Mexico offshore region."
" low velocity sediments "
= slow gas drift vertically
" sliding on a sub-horizontal surface "
= rocks tend to be aligned in layers horizontally
" We modeled the observed surface waves using a single-force source (e.g., 5), often referred to in the academic literature as a "landslide"
source. "
http://www.onepetro.org/mslib/servlet/on...
-------------------
Insights into the mechanism of the Northern Gulf of Mexico MS 5.3 "Green Canyon event" of 10 February 2006
Authors:
Dellinger, J. A.; Blum, J. A.
Affiliation:
AA(Advanced Imaging Team, BP America, Houston, TX
" Although the Northern Gulf of Mexico is generally a region of low seismicity, it produced three earthquakes of magnitude 4.5 or greater in 2006, including a MS 5.3 event in the Green Canyon area on 10 February. This "Green-Canyon event" was of particular interest because of its proximity to offshore hydrocarbon exploration and production facilities "
--------------
A model for fluid-injection-induced seismicity at the KTB, Germany
" The 9.1 km deep KTB (Kontinentale Tiefbohrung, Germany) drilling hole is one of the best investigated deep-drilling sites in the world. Among other parameters, in situ measurements revealed continuous profiles of principal stresses, pore fluid pressure and fracture geometry in the vicinity of the borehole. The present study combines these parameters with hydraulic and seismicity data obtained during fluid-injection experiments conducted at the KTB to derive a conceptual model for fluid-injection-induced seismicity at the KTB. This model rests on the well constrained assumptions that (1) the crust is highly fractured with a permeable fracture network between 9 km depth and the Earth's surface and (2) the crust is in near-failure equilibrium, whereby a large number of fracture planes are under near-critical condition. "
http://www3.interscience.wiley.com/journal/118846782/abstract?CRETRY=1&SRETRY=0#ss4
....so they are going to use a light mud, water-based, this is an indication that the rock layers that the leaking in has a high pore count, enabling rapid drifting of fluids and gases. They do not want to frac' the reservoir, or the damaged bore any more than it has already been frac'ed
The cap may have, and probably does, imho, have a leg of gas, or a saturated/gas cut leg of fluid in the bore.
..The following was pasted from the comments at:
http://www.flickr.com/photos/uscgd8/4551846015/page63/#comment72157624626346300
BP will not use oil based mud on this, a) its too expensive, b) it entrains gas. c) They are not going to produce this well so formation damage is moot. d) It is even more environmentally unfriendly than crude oil.
"Lubricate and bleed" be done in a controlled and slow fashion that would not raise the pressure much? If they injected at a very low rate through the choke line (using a cement pump) while producing a similar amount of fluid through the kill line, the pressure rise would be minimized. They would have to inject at a rate of just gallons a minute, but if the fluid is dense enough some/most would be displaced down hole. Whether it would do any good is still to be seen.
Why not use heavy brine for the injection fluid in "Lubricate and bleed"? It would fall through the oil and slowly mix with the entrained formation water, but at least add to the hydrostatic head and lower the pressure (if it is falling in the oil flow path).
That's how it works, they will be there trying to kill this thing this time next year.
If they try and bump and bleed at the same time the mud will just flow across the stack and back up to surface, that's what they accomplished with the first top kill ... waste of mud and time.
" lubricate and bleed kill methods are for gas wells "
My concern is that something else will give before the fracture initiation pressure is reached down in one of the weak shales in the open hole. The BHP of the sand is a good deal lower after the several million barrels of production and the weak zones are maybe hundreds of psi above where fracture initiation would occur.
If I understand this correctly, the ideal way to “lubricate and bleed” is to inject some heavy mud into a column of gas. Then the heavy mud falls through the gas and increases the hydrostatic head on the BHP, which lowers the pressures everywhere. The gas column/cap returns back to the top of the well and the process is repeated until the BOP pressure is greatly reduced. So if only we had a gas cap this might work – except we all agree that a gas cap is unlikely.
Of course the scenario of something other that a weak zone in the open hole breaking is the worst case and the reason other options would be taken. The fracture initiation pressure of any zone is in direct proportion to the reservoir pressure in the zone and so if the pay zone has been drawn down, and it has, then the payzone will likely be the zone that will fracture and the oil will simply go back from whence it came. That is what will happen.
Yes, under the gas well scenario the lubricate and bleed method works great and quickly. When the fluid is heavier it takes longer for the fluids to redistribute and stabilize and it would take a very long time to accomplish a lubricate and bleed. They likely would simply keep bullheading once they realize how easy it is.
Like I said before, the reason they won't to do the bottom kill method is that they, unlike us here, have not figured out that the blowout was flowing up the annulus and so there bottom kill would involve milling casing whereas it isn't necessary.
The 7" could be holed by now given the time and flow rate, it 's possible it has washed out opposite the producing zone, and or, the 9-7/8" liner shoe. These are the two places where the annular velocity is the highest. I would imagine there is not much left of the casing hanger either.
From the reports this morning it seems the hole on relief well #1 has sloughed in on them during the non-storm. Most likely it is sloughing because of the pressure build up in the surrounding formations because of them having the Macondo shut in.
I hope the genius' realize that before they drill much closer to the well bore, or we will be drilling another relief well for the relief well.
http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Structure/fatigue.htm
The Effect of Fluid Loss on Fracture Initiation During Squeeze Cementing Operations
http://www.onepetro.org/mslib/app/Preview.do?paperNumber=00019384&societyCode=SPE
HYDRAULIC FRACTURING
http://spe.org/spe-site/spe/spe/jpt/2007/03/Syn103232.pdf
If I understand it correctly, in the bottomkill without returns to the surface, the pumped mud/cement would flow to the weakest zone (probably the pay sand now). So there could still be a column of cement from the penetration point of the relief well down to the pay zone, at least in the annulus. But a concern would be if there were holes in the lower and upper casing that provided alternate flow paths. We have no idea what shape the production casing is in.
The entire “lubricate and bleed” idea is foolish with the relief well so close to being useful. Increasing the pressure on the system is the opposite of what they should be doing.
Excerpts from today’s NYT:
-quote
Officials Optimistic That Cement Will Kill BP Well
By CLIFFORD KRAUSS
The static kill, also known as bullheading, is part of a two-pronged strategy to kill the well by cementing it shut twice, once from above with the static kill and then from below, using a relief well.
The approach has been compared by some engineering experts to the folkloric efforts to kill vampires.
…
“The well can only be killed from the bottom up,” Admiral Allen told reporters last week.
Still, he added, the static kill is important in large part because it can help determine the stability of the well. If there is a sudden drop in well pressure as mud is pumped into the pipes, that could mean there is a leak somewhere in the well. In that case technicians could seek out the leak with seismic work and other diagnostic testing, and then tackle those leaks with the cement pumped in through the relief well.
…
“No one has come out and said the well has full integrity,” said Greg McCormack, program director of the Petroleum Extension Service at the University of Texas, Austin, suggesting that it was still possible for the well to leak before the relief well was completed. For that reason, he said, the static kill operation makes sense to potentially kill the well two weeks earlier than the relief well would.
“This is just an ultraconservative approach,” Mr. McCormack said, “and at this point in time we should be taking the most conservative approaches. I can’t see any risk.”
-unquote
-------------------------------------------- -----------
“This is just an ultraconservative approach,” Mr. McCormack said, “and at this point in time we should be taking the most conservative approaches. I can’t see any risk.”
With petroleum “experts” like McCormack, we’re in trouble. It’s scary that they get quoted in the press while the sensible approach only got one line and were referred to as “some engineering experts”.
BP still wants to cement the BOPs up so they can't be retrieved,
That is the only logical conclusion.
Any person that has ever killed a well, knows you can't do it the way they are saying, it simply will not work.
Leaving 9/10ths of the hole full of gas cut oil is not only stupid, it's insane, and illegal by MMS rules or whatever they call themselves now.
Plug the top after the well is dead.
Put a rig over the hole, fish out the junk, cut the casing and pull it out, and put a bridge plug in the hole, retrieve the BOPs, fill up the hole with cement, end of job finished.
There is no such thing as acceptable risk, you minimize the risk by proper engineering and planning to the point where it's just a difficult job at most.
It does seem like having the old hole available to flow out of when they flow cement into the relief well would be nice. To plug the old hole with cement before cementing from the relief seems bogus.
This is way past just plain dumb. It's almost like watching a kid trying to see how much he can get away with. Given where we are with the relief well, this is a new level of crazy. Surely the press got it wrong.
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So, after reading those people who work in the industry, it gave me a good insight into what the potential problems might be here.
The events of erosion are time dependent, the longer they go on the worse they get. The events of erosion's under immense pressure, and high temperatures drifting through unknown natural fractures, and rock layers of various densities, and possible sand traps . With a highly sedimentary binary fluid containing suspended gases at different bubble points, moving at high pressure through who-the-hell knows-what...
There's only two event's that can happen....the holes get bigger....or the layers cave in and block any holes or paths. " Bridging " After bridging occurs...that's only the fluid path really....the gases began to then drift , at different rates , according to rock pore counts....and then there are also many old bores in this area that have been cemented and abandoned in block 252.
Like many have said before...they knew it could happen, and probably would happen back in February. This event has , and is, being milked for every dollar, in every way.
I feel like the longer they wait, the worse the potential screw-ups could be....good luck, guys.
