oh lord please help me 1

[dcasto]

the Internet is going wild with non engineers claiming to know that they know how to fix the BP blow out. I have been trying to tell non-engineers that the hydraulics of oil coming from 500 feet deep are such:

5000 feet of salt water has about a 2500 psi at the wellhead. The oil, if captured in a "tent" will have about 25% (based on a .75 gravity) of the 2500 psi or 500 psi pressure at the surface.

they look at me and their jaws drop and say "its at air pressure" so it can't be 500 psig.


Wow, if I'm wrong, how do salt dome storage system work.


I'm sorry, this should be in a rant forum, but, the unbelievers have ENGINEERING DEGREES.... do you have any good links, I'm tired of throwing out my ChemE books, they only believe links....

 

[zdas04]

You should see the crap on the non-technical web sites. Everyone is certain that (1) it could have been EASILY prevented and was only allowed to happen because BP went cheep on their multi-billion dollar well; and (2) BP should be punished for their greed. At least stupid "pseudo-engineering" solutions can be debunked with Engineering Principles. The conspiracy/communist nonsense can't be contained. There's one in the pub that made me want to delete the pub from my threadminder.

One thing I've learned both in the classes I teach and in posts here is that you simply cannot teach fluid mechanics in sound bytes. If the "student" is not going to do the arithmetic required to master the concepts then they are going to persist in believing that everything you ever needed to know about fluid mechanics can be learned from a garden hose and blow-up swimming pool. Any system more complex than that is just "elitist nonsense".

I feel your pain.

David

 

[BigInch]

I obvioulsly agree. Every inter-nut engineer is absolutely spewing. However there is some common sense that is showing through from time to time. There is indication that 1 BOP cannot be counted upon as the measure of last resort of sufficient reliability at these sea depths to act as the measure of last resort. And it would also seem that stocking one or two of these capture bells for use in emergencies would have been prudent rather than having to wait a month while one is fabricated. So my inter-nut guess is the computer precicted 1 BOP failure in a million years, but didn't consider a drill rig sinking on top of the BOP is much less and when that happens, the BOP's probability of failure increases to 300%... 3 tries failed.

Having lived on the Gulf Coast for 35 years and throughly enjoyed the culture, fishing and scuba diving, I can only hope that the environmental damages and suffering will not be as severe as what some are predicting.

I am also beginning to wonder if it was just a simple coincidence that the only expert testimony that I have ever had occasion to submit to English Parliment happened to be contradicting a number of decisions taken by contractor's of this very same operator. Fortunately I haven't bought their gasoline or their stock for about 8 years now, often at some inconvenience, as they do actually have the second closest gasoline station to my house, so I'll be well ahead on the boycott curve.

Predicting failure modes in complex systems is limited by man's ability to understand complexity, which by definition, is essentially something too complex to understand.

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[rneill]

I have been party to many risk assessments both for onshore and offshore facilities. There is sometimes a tendency to discount these "rare" incidents as unrealistic and not adequately address them. Senior experienced folks sometimes believe that if they have not witnessed or personally heard about that type of event, it is not realistic. However, given the consequences of events like this, we need to be targeting a level of safety that is far beyond that for which personal experience can attest.

It has always bothered me a that for offshore facilities there is a general target level of safety that the probability of an incident like this should be less than 1 in a million (and we always seem to conclude that we have achieved that goal) but the practical evidence (the number of disastrous incidents that occur worldwide) seems to suggest that we may be a long way from this target.

I believe that some Operators can do much better both in terms of the level of safety and redundancy built into their facilities and in terms of effective preparation to deal with such contingencies.

I have never worked for or with BP, either directly or indirectly, but two major accidents with National attention within a 5 year period (Texas City and now this) would suggest that perhaps they are not fully engaged in, and appropriate tuned to, the risk management process.

That said, in the last couple of years, more and more of the Companies I work with have been touting the mantra of "Code Minimum" and seeking to reduce costs by eliminating "un-necessary" excessive and "gold plated" engineering and design, by buying less expensive equipment, and by reducing the level of review and oversight that they provide (and the quality of the personnel who perform this work).

Regarding the capture bell issue, the differential pressure would be very high if the tent extended the full depth of the ocean. If as is more likely the case, the tent has a height of only a few feet then the differential pressure would become insignificant. I think the idea would be for the tent to simply act as a funnel to collect some oil and to provide temporary storage while it is pumped away. To do this, the tent needs a certain volume capacity which could be achieved with a large width and length and small depth.

Note: Previously, I worked on a large offshore platform consisting of a gravity base structure (GBS) which had oil storage cells in the GBS extending from ocean bottom to surface. The water depth was not particularly significant but as suggested by dcasto, the oil exerted a high pressure on the roof of the storage cell and we had ongoing issues with having to repair cracks that developed in the concrete roof of the storage cell.

Regarding the issue of the wellhead/BOP, has anyone ever considered the idea of placing some sort of a structure over top of the wellhead/bop to provide some protection against mechanical impact ?

 

[ccfowler]

Since I have no experience with oil production, I freely admit that my thought may be a practical absurdity.

While thinking of this as both a Gulf Coast resident and an old geezer mechanical engineer, it came to mind that perhaps some large but fairly simple mechanism could be lowered into position to squeeze the pipe below the level of the leaks effectively creating a giant pinch valve to at least drastically reduce the flow until more permanent measures could be completed. I'm thinking in terms of a couple of opposing large rounded bars that could be squeezed together by a couple of large hydraulic cylinders or large powered screws. I presume that some means of supporting the upper portion of the pipe may be necessary to stabilize the deformed pipe.

Is this absurd, or could such a device be a potential aid to solution of the current problem? My thinking is that such a device could be fabricated and implemented relatively quickly.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[rneill]

ccfowler,

Wells are normally equipped with exactly such devices intended to ram the vertical tubing and pinch it shut in an emergency. I assume these wells had such devices and that they have been unable to operate them possibly due to damage that occurred during the rig accident.

 

[BigInch]

Shearing off the drill stem is the function of the BOP. It goes without saying that it would be much more difficult to place that assembly below the mudline.

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[unclesyd]

You can add the spill from the pipeline in ANWR to BPs resume. I'm not totally against drilling I'm bad prejudiced
against the oil companies and the way they operate. I fish in the general area of the spill quite lot and have made many trips to west and north of the area snapper fishing.

Look at thread470-270414: Rig Explosion and Fire there are several links to some good information on and about the spill. The government report and the BP presentation are quite interesting. The gov. report contains information on the Sombrero capture device that was tried on the IXTOC 1 blowout.

Here are the capture devices being built.

http://news.yahoo.com/s/afp/20100427/ts_alt_afp/usblastoilenergypollution_20100427170112

According to some reports the leak seen on a lot of videos is at a joint 1500 feet off the sea floor. Another kink that is leaking is very near the outlet of the BOP which 50 + feet high.

I thought about the same thing but it would take a hell of a clamp to pinch off the riser pipe. We routinely pinches off 1" and 11/2" lines but we had one terrible time in trying to pinch off a 4" Sch 80 CS line.

As I posted in the referenced thread I can't see how they though they could operate the BOP without hydraulic power unless there was a very large accumulator attached. They took the hand wheel, about 3-4 feet in diameter, off BOPs many years ago.

 

[dcasto]

the rig sank 1300 feet from the wellhead. The sheared off riser is 5 feet from the well head.

I do agree with biginch about having a tent ready to go, it's a cheap insurance for use at all wells. The other arm chair QB'ing is on a 3rd switch to activate the BOP. If the light bulb is broken, then 100 switches in parallel won't change a thing.

 

[BigInch]

USCG has a photo stream on Flicker going here,

http://www.flickr.com/photos/uscgd8/page2/

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[unclesyd]

I think if you go back and check the information you will find the riser isn't broken off at the BOP it is kinked in numerous places and in two places it is cracked and leaking with the third leak being at a broken joint.
According to some the kinks are acting as restrictions so the well at the present isn't an uncontrolled gusher. One of the worries is that sand will scourer the the pipe at the kinks.