Failure of Rig’s Last Line of Defense Tied to Myriad Factors ( Deepwater Horizon BOP Fails )

The New York Times ^ | June 20, 2010 | David Barstow, Laura Dodd, James Glanz, Stephanie Saul and Ian Urbina.

[Ernest_at_the_Beach]

It was the last line of defense, the final barrier between the rushing volcanic fury of oil and gas and one of the worst environmental disasters in United States history.

Its very name — the blind shear ram — suggested its blunt purpose. When all else failed, if the crew of the Deepwater Horizon oil rig lost control of a well, if a dreaded blowout came, the blind shear ram’s two tough blades were poised to slice through the drill pipe, seal the well and save the day. Everything else could go wrong, just so long as “the pinchers” went right. All it took was one mighty stroke.

On the night of April 20, minutes after an enormous blowout ripped through the Deepwater Horizon, the rig’s desperate crew pinned all hope on this last line of defense.

But the line did not hold.

For days, technicians and engineers worked furiously to figure out why, according to interviews and hundreds of pages of previously unreleased notes scrawled by industry crisis managers in the disaster’s immediate aftermath.

Engineers sent robotic submersibles 5,000 feet deep to prod the blind shear ram, nestled in the bosom of a five-story blowout preventer standing guard over the Macondo well.

They were driven on, documents and interviews reveal, by indications that the shear ram’s blades had come within a few maddening inches of achieving their purpose. Again and again, they tried to make the blades close completely, knowing it was their best chance to end the nightmare of oil and gas billowing into the Gulf of Mexico.

[Ernest_at_the_Beach]

Are you referring to the video and the graphic shown ... there at the website...which I see fine.

[Domangart]

Dr Bill KGO radio. The well head is about 3,300lbs but if you attempt to close it then the pressure will increase to 175,000 lbs I recall the diving math was something like 33ft=14.1lbs times 5000 feet and the drill is at 18,000 feet plus the earth pressure at that level

[Ernest_at_the_Beach]

I don't understand how he would arrive at that pressure...I'll see if I can fine the thread at the Oil Drum where they talk about the pressures in the well at various points ...all less than 20,000.

There is a deep NG well in the Anadarko basin in Western Oklahoma where the down hole pressure is close to 30,000 psi.

Guess it is pressure at the BOP:

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[Ernest_at_the_Beach]

Nite all.

[JohnQ1]

...and while BP fought what they feared was coming, Obummer was taking his ongoing cut of BP’s profits and handing safety awards to the least “safe” oil Company extant. Sheesh!

[proud_yank]

The well head is about 3,300lbs but if you attempt to close it then the pressure will increase to 175,000 lbs I recall the diving math was something like 33ft=14.1lbs times 5000 feet and the drill is at 18,000 feet plus the earth pressure at that level

There are two different pressures to consider- wellhead pressure and hydrostatic pressure (pressure of water at depth x). You can't use the well depth to determine the hydrostatic pressure.

IIRC, the wellhead pressure did not exceed 15,000psi. The 3300# you mentioned may be the hydrostatic pressure of the ocean. When I calculated it I got 2170psi for 1515m (5000ft) depth, assuming the density of seawater= 1000kg/m3.

Don't know what would create 175,000#, that is incredibly high.

[Domangart]

Its not my field. I didn’t build atomic bombs , teach physics and put out oil fires. He has the degrees and he said 175.000 lbs.

[Domangart]

Dr bill has the degrees and experience and he said 175,000 lbs He tends to get a little testy at people who slept thru science. It has to do with attempting to secure a valve and the pressures on that valve.

[proud_yank]

Its not my field. I didn’t build atomic bombs , teach physics and put out oil fires. He has the degrees and he said 175.000 lbs.

He's most likely referring to the cutting forces of the shear ram on the blow out preventer (BOP) required to cut the drill pipe.

It would be impossible for the wellhead pressure to rise if capped, especially to that amount. Unless, you somehow placed an explosive inside the reservoir and detonated it or drilled an injection well hooked up to one massive pump that can create pressures that high (which does not exist).

In other words, say the reservoir pressure is 15,000psi exactly, if you completely seal it off it will remain at 15,000#.

I work in the field, have taken plenty of physics courses, have an appreciation for atomic bombs and (hopefully) my only experience with oil fires is when using it to burn brush:)

[raygun]

well-head pressure is approx 13k psig. As long has the well-casing is burst resistance rating higher than that, we’re good to go. Hydrostatic pressure at 5k’ has no bearing at all on this figure whatsoever.

My understanding is that the burst rating of the well-casing was marginal. This allowed segments of the well-casing to balloon out and in a non-uniform manner. This also affected structual integrity of the well-casing string in the vertical and directionality of the bore-hole was also affected.

It was a nightmare aligning and sealing the borehole because of all the aforementioned issues combined. The coup de gras was the failure to emplace a liner hanger in the furthest downhole section of well-casing. When the drilling mud was removed and replaced with sea-water, the oil/gas at 70,000 psi - in resevior - had a clear shot to the top. That cleared out a bunch of the cement sealing the well-casing to the bore hole.

As I understand it, some of the well-casing telescoped into itself, and upwards into the BOP. The shear rams are designed to shear riser pipe (not well-casing). If the You Nork Slimes article is 1/2 way accurate, which I doubt (given that the journalist quality of any 5th grader’s reporting for the school newspaper is by leaps and bounds superior quality), the claim that the rams were within inches of securing the blowout suggests the the strength of the shear rams in any case.

[Leisler]

It’s tricky to for the New York Times to extract their lips, long since grafted, from O’s butt and not leave any scaring.

[jonrick46]

I was commenting on what Revel posted on #6. Not too sure what Revel said, but I chose to take it literally.

[norraad]

http://www.youtube.com/watch?v=qynVhnL5cf0

[eddie willers]

This is one of the few instances where you’ve got to give props to the NY Times.

They used their size, resources, contacts and pedigree to bring a comprehensive report that probably no other entity is capable.

They then reported it in pretty much “Just the Facts, Ma’am” style and let the readers draw their own conclusions.

Something I thought I’d never say...”Good job, Times.”

[mo]

i’m goin’ out on a limb here...but I don’t think modern administrators have enough reality grounding to attempt or supervise complicated projects. Their illusions interfere with reality.

[Ernest_at_the_Beach]

And with this administration the AGENDA messes with the facts.....

Was just looking at this little conference the Obamaists have set up:

Clickable Logo

[jimt]

Dr Bill KGO radio.

Dr. Bill needs to look for better sources.

Well logging instruments are designed to take any expected pressure from surface to touch down at the bottom of the hole.

Most are designed to 20,000 psi. Newer models when I worked at a logging service provider were designed to 25,000 psi. We tested some parts to 30,000 psi, but those were parts of measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools.

30,000 is nothing to sneeze at, but certainly not impossible to work with. I designed and built a pressure test chamber for that pressure, and proof tested it at 45,000 psi. The top screwed on (and unscrewed) by hand and it was sealed with a single o-ring.

Modern waterjet cutting systems run at 50,000 psi or higher. Parts are commercially made that are rated at 60,000 psi (see Autoclave Engineers).

The wellhead pressure, shut off, is nowhere near 175,000 psi. If you had a valve on the pipe and slammed it shut in milliseconds, you would get a hellacious pressure surge. But the equipment we're discussing doesn't move that fast. Dr. Bill is wrong.

[Marine_Uncle]

I have to save this one for more detailed read. Many interesting points are made that have not been covered elsewhere icluding the Oil Drum. Quite detailed report.

[Domangart]

He was talking about placing a valve on the pipe and the closing pressures.