BP Gulf Coast Oil Spill Q/A 1

[ninja99]

Informational and brainstorming thread about the recent coastal oil spill. Petroleum engineers' professional opinions greatly appreciated!

The story thus far:

Press release:

http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7062470

Live cam:

http://www.bp.com/liveassets/bp_int...local_assets/bp_homepage/html/rov_stream.html

Related articles:

http://www.cbsnews.com/video/watch/?id=6490509n&tag=contentMain;contentAux

http://www.deepwaterhorizonresponse.com/go/site/2931/

http://www.api.org/Newsroom/safetyresponse/index.cfm

Some questions:

With the doubled pressure on the underwater rig (due to mud being pumped against the oil flow), could the structural integrity be weakened? What are some of the worst-case-scenarios if this were to happen?

What are some other methods to resolve the situation? Be it via relief well, junk shot, etc.

What are the long term effects on the surrounding area?

 

[unclesyd]

Last question first. No one really knows for sure. The thinking goes from complete loss of the Delta, if a storm comes in to a lot of habitat for sea creature and rookeries for birds. The oil in open ocean is another unknown due to the quantities and where it goes. The Gulf can accommodate some oil as it does with the natural seeps.

The only real solution is the relief well. This can be troublesome as the 1979 Itox Blowout, BOP, took 9 months to completely seal and it was shallow enough for diver to work on the well head. BP has acknowledged two heavy "junk hots" as well as smaller injections.

There was big worry that BOP had been damage by the collapsing riser but apparently was effected. The biggest problem now is the pressure need will be too much for the kinked drilling riser. They only have two injection points to inject the mud into the BOP. I haven't heard what size these lines are. One is the coke line. BP still refuses to give the pressures involved in any aspect of the process. One professor from a Texas school stated that that if will take 3000 ft of 16 pound mud to kill the flow.

 

[waross]

Hi unclesyd.
With the partially open BOP and the flow of oil, will that not act to vent most of any pressure rise the mud pumping may cause?
What is 16 lb. mud? 16 lb. per gallon? 16 lb. per liter?
Thanks.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[owg]

You can get live video of the BOP and surrounding areas at

http://www.cnn.com/video/#/video/us/2010/05/28/vo.aerials.oil.rig.cnn

. The link may change from time to time. When the camera is close to the BOP you will see the two injection pipes clearly, they look quite small. The idea seems to be that they pump so much mud in that the amount gushing from the BOP creates enough back pressure that some of the mud goes down the hole. Do that with enough mud for long enough, you should get an adequate column of mud in the hole. Please feel free to criticize this interpretation. I have never been near this type of well and I am just theorizing.

HAZOP at

http://www.curryhydrocarbons.ca

 

[dcasto]

16 pound mud is 16 lb per gallon or about .83 psi/ft. This would put 15,000 psi bottomhole. The well blew out with seawater and was under control with normal mud. This would lead one to believe that the bottom hole is between 9000 psi and 15,500 psi. The 15000 psi is 1 psi/ft for the 13,000 feet of drill depth plus 2500 psi for the water pressure.

 

[unclesyd]

Here is the scheme of things supposedly as it now stands.

http://www.reuters.com/article/idUSN2819681720100528?type=marketsNews

A strange place to find information. Go down to the "Oil Drum" Leak header and read more.

http://www.petsstatus.com/archive/lower+marine+riser+package.html

BigInch
Here is primer on Drilling fluids.

Thanks for the analysis. The CEO has been asked about some of the pressures involved several times and his comments are always that everyone is too busy to provide any outside information.

http://www.wdcexploration.com/what_we_do/pdf/drilling_fluid_fundamentals.pdf

Checkout BigInch's reply of May 29 @ 6:53 in thread311-2715. One or two hard numbers from BP and his analysis would tell you exactly what's going on. Apparently they are giving this information to anyone not even the US Government. Our government people at all levels measure the money received from the oil patch in barrels.

Addenda:
Early on in the reporting of this event there was an interview with a survivor of the accident who was in a position to give some of the preliminary events. One of his comments was that some time before the event happened a mud pump operator reported that he was finding relative large chunks of rubber on his filter screens on the returning mud. This gentleman said that this rubber could have only come from the "annular valve" at the top of the BOP. As I understand it the purpose of this valve is to seal the annular space between a restricting bushing and the drill pipe when they want to shut the well off from the riser. He stated that someone inadvertently pulled about 15' of drill pipe through the closed valve. This valve acts like a hydraulic collet.

My in-laws who work offshore had been put under a "Don't Tell if Asked" policy. To get close to the truth about about the events preceding the accident it would take a criminal indictment to get even half truths. Have them brought before a Federal Grand Jury and have a jar of Petroleum Jelly on the table.

If you get a chance checkout the National Geographic Film. Right at the end you can briefly see a very large oil flow from the well head with an unbent riser. It worries me if they cut the drilling riser below the kink they could possibly have this flow again.
If you listen to the comments and pay close attention to the events being recorded you will see that this was being treated as a shipbord/rig fire almost to the end, evidently no one wasted to say this was wild well on fire. The fire fighting crew from Holland was experts in shipboard fires. In fact you will note that they were preparing to salvage the ship.

 

[rmw]

Unclesyd,

I couldn't find BigInch's reply in that thread.

Can you repost please?

rmw

 

[unclesyd]

If I could get it right it might work.

Checkout BigInch's reply of May 29 @ 6:53 in thread311-271544.

The third heavy "Junk Shot" apparently has not worked. They are saying 24 hrs but have a news conference in one hour.

Addenda:
The reported potential of this reservoir is 50,000,000 barrels. Also all the while this "Junk Shooting " was going on the flow of "hydrocarbons hasn't changed only a small change in the gas/oil ratio

 

[unclesyd]

An very interesting read.
The thing that bothers me is this was a drillship. That means it was a ship under maritime regulations and on a ship there is only one person in charge and that is the Captain.

http://online.wsj.com/article/SB10001424052748704113504575264721101985024.html?mod=wsj_india_main

 

[unclesyd]

"Top Kill" has been killed!

 

[owg]

After "Top Kill" comes a plan to cut off the pipe at the top of the BOP and put a better funnel over it. I was wondering why they can't give the robots impact wrenches and unbolt the top. Then they could lower the next BOP down and bolt on top of the current BOP. Then close a few valves.

HAZOP at

http://www.curryhydrocarbons.ca

 

[unclesyd]

owg,
I have conveyed to my friends who have some contact with people on working site to look at hydraulic nut busters in lieu of any type wrench. This would do the same thing, but breaking the flange will still require the cutting of the drilling riser to take some pressure off the gasket.

To add another blowout preventer as I understand it will have to have it's separate support frame as the riser below the current BOP can't sustain the additional load. Any larger leak would require that a vessels in the area where the oil surfaces would have to move due the possibility of fire where the oil surfaces. I tried to get a number on this but had no luck.

I heard two comments yesterday and today that relieves some of the a big concern of mine. Flow out of the riser is limited by the pressure drop taken in BOP stack. I just hope it will not be the flow seen in Nat. Geo. Film during the filming of the drill ship fire.

 

[unclesyd]

One of them brain thing A big question. When this episode started there were three leaks one at top of the BOP still leaking, the second at the end of the broken drilling riser still leaking and the third at the end of drill pipe that they easily capped
The drill pipe goes through the BOP to some depth and would become a conduit for oil if as proposed they square off the Drilling Riser with a diamond wire saw. There is also a kink at the top of the BOP like the drilling riser that may have restricted the flow so they were able to cap it. I don't know the diameter of this drill pipe but I've heard 7" several times.

 

[owg]

Thanks to unclesyd for the very helpful responses. I was wondering if the drill pipe still goes through the BOP. Now I am wondering how the BOP was supposed to work. Are its functions 1) To provide a seal around the drill pipe? (There were reports about bits of rubber/sealant showing up in the mud. 2)To provide closure when the drill pipe is not in the way? 3)To provide closure around the annulus when the drill pipe is in the way? Thanks

HAZOP at

http://www.curryhydrocarbons.ca

 

[unclesyd]

The case is thus or somewhat similar.

If the drill pipe is still passes through the BOP there is a rubber seal that can can be externally energized to seal the annulus at the top of the BOP. This valve can be used during any type of operation below the BOP. There are a number of different variation of this valve.

Below this valves there can be a number of different type hydraulic valves that can be used to stop the flow if there is no drill pipe in the BOP. If there is is drill pipe in the BOP there are pincher valves that are designed to pinch, not sever the pipe to stop the flow. If activated one has to pull the string of drill pipe to replace this section.

The last line of defense is the shear valve which which when activated will completely shear the drill pipe and shut the well in. This is the last resort. I don't know the configuration of the valve on the DWH BOP so I have no idea if they could have recover from the activation of this valve. It can be done on some BOPs but is very time consuming and expensive. Two BP wouldn't stand for as they had lost two months, getting in a hurry, will drilling this well.

The type of BOP used on this job is very complex in itself and with the controls.

The radiography accomplished right after the event was able to show that the pincher valves were partially closed. The reported low hydraulic pressure reported early could account for this.

I've been told by several people in the business that the reason for the change from drilling fluid to salt water was money. BP would have been able to use this mud on another well saving a ton of money as the weight was 16 pounds, very costly.

 

[waross]

I am wondering why the depleted hydraulic pressure can not be rectified in the BOP.
With all the things that they can do with the remote operated vehicles, why can't they clamp and pierce a hydraulic line and increase the hydraulic pressure?
Is the BOP itself under designed and not able to function even with full hydraulic pressure?
Is anyone else starting to suspect that the BP honchos will still dismiss any idea that doesn't originate in house?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[unclesyd]

They were able to hook up the two hoses for pumping the drilling fluid. I see no reason why what your propose couldn't have been made to happened. I've asked the same question to some people who work on these things everyday and have not gotten a full explanation of why not.

In the information being disseminated there has been mentioned about a hydraulic leak with nothing about where it was. If it was on the servo circuit this could be a reason or the mention of a low battery which may have prevented the operation of a servo valve that would allow this to happen. If you check the interview with the rig electronics head you will hear that all the engines started sunning away very close to the time the gas first started escaping. This killed all the power on the ship and probably took out the BOP console on deck as they immediately lost dynamic positioning system which may have severed connections to the BOP.

On another discussion group a person with the handle "horizon 37" who if not part of the operation was very close to it said a good possibility was that the drill pipe was set with a joint in shear rams path and there wasn't enough power to shear it. This is quite plausible as the Williams interview on 60 minutes mentioned that the drill pipe had had been inadvertently raised about 15 feet.

Getting to the truth about what happened before and during the incident will be impossible as anyone in supervision will lie and the workers on deck can't say anything as they will be blackballed, probably their family too.

 

[waross]

I understood that the raised drill pipe incident was about one month previous and that is what may have trashed the inflatable annulus seal.
I understood from one of the interviews that the cementing crew tried to activate the missing annulus seal. I guess the regular crew didn't tell the cement crew;
"Oh, by the way, the annulus seal is trashed."
I have no idea of the separation of the hydraulic circuits on the BOP but the missing inflatable seal may have been responsible for the hydraulic leak and low pressure.
I don't know, I am asking. Please don't take my suggestions for fact. I'm asking questions based on a basic mechanical knowledge and bits and pieces of information gleaned from various press releases.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

I assumed that the engines were ingesting methane gas as the reason for the run aways. I was aghast that they would be running without automatic shut down flaps in the intake manifolds. Then we started to hear about BP's disregard for safe practice in general.
I am still some what aghast, but no longer surprised.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[unclesyd]

That was my opinion also and the air intakes were inboard and evidently got the gas first. There is one report that an attempt was make to start the backup generators and they wouldn't even turn over. The report stated that an interlock had them locked out and couldn't be reset.

I was slightly in error about the shear rams on the BOP. On this one there are two one and and one lower. The top ram is supposed to shear the drill pipe and the lower to cut the casing and possibly squeeze the drill pipe.

Here is live feed of the bots working at the top of BOP stack.

http://www.livestream.com/wkrg_oil_spill