In depth: The Deepwater Horizon BP oil spill cause

I’ve been meaning to write a more comprehensive post about the Gulf oil spill for more than a week and this post is my attempt to do so. But first I want to quickly note President Clinton’s comments about blowing up the well, and why some engineers think it’s a bad idea.

Update (July 30, 2010): The Center for Public Integrity has a report about decisions made after the explosion which you’ll find to be a good compliment to my post below. (Hat tip to Ed Morrissey at Hot Air.) Back to the original post…

In the high-tech oil drilling community – who happen to have some really smart engineers – there is a concern the well casing has been compromised beneath the sea floor. For an analogy, think of the well casing as a garden hose, and the all-famous blow-out preventer (BOP) as a spray nozzle from which you can control the flow.

Imagine the garden hose vertically underground and the spray nozzle just above ground level. Now imagine underground critters eating away at the hose a few feet below the surface. The critters eventually break through the lining of the hose allowing water to leak underground and bubble up and around the spray nozzle.

In this bad scenario, the casing could collapse and the BOP could just tip over as the sea floor support eroded over time. Oil. Spews. Everywhere.

Equally relevant – especially to novices – is the opinion from engineers that the BOP and the casing are so big and strong, collapse is unlikely. The BOP is connected to a 2 inch thick steel pipe that is 3 feet in diameter, extending more than 250 feet into the sea floor. This pipe (casing) is connected (cemented joints) to subsequently narrower pipes of 28 and 22 inch diameter continuing more than 2,800 feet below the sea floor. It’s a strong structure.

Although the federal government has all but taken the blow-it-up-with-a-nuke option off the table, that does not mean consideration has not been given to blowing it up and stopping the flow using conventional means as Clinton suggested. (Hat tip to Hot Air.)

In my opinion, the speculation that BP is trying to save the well to ensure they get oil from it in the future is completely absurd. Clinton, nuclear submarine officers, and congress-critters wondering why BP has not just stuck some dynamite down there and blown it up to stop the flow immediately is equally absurd.

Do we even have the technology to do this one mile underwater? What are the risks involved? Could blowing up the well result in the first engineer’s disaster scenario above?

So, what happened out at Deepwater Horizon?

The following is a brief primer on oil well drilling basics pieced together from various sources along with some analysis as to what may have happened.

On June 11 I read a letter to the editor from Terry Barr, president of Samson Oil and Gas in response to an Op Ed piece written by Tony Hayward, CEO of BP plc. Two Radio Vice Online readers – a recently-graduated oilfield engineer (Craig P.), and a corrosion engineer (Dan P.) with decades of experience including many years in Prudhoe Bay, Alaska (a.k.a The Slope) – gave it a shot at translating for the masses.

When wells are drilled, casings and BOPs are installed before the wells are completed. First you drill a wide-diameter hole to a specified depth to create the first part of the well bore. Matching the depth of the first part of the hole, the casings go in next. They are big, thick steel pipes going down the well bore (the hole that is drilled).

When first placed, the casing “floats” inside the drilled hole. The casing is centered within the hole and concrete is pushed down the hole to the bottom and comes back up into the void between the outside wall of the casing and the inside wall of the hole.

After the first casing is cemented in place, more drilling takes place (if needed) and more casings are added deeper within the well bore. These additional casings are progressively narrower in diameter since they need to fit within the walls of casings above.

The cement in the void prevents natural gas or hydrocarbons from escaping. You want the oil and gas to eventually come up inside of the casing, not along the inside walls of the well bore.

You keep going as required, and before you hit the oil and/or gas reserve, the BOP is placed and tested.

For Deepwater Horizon, it appears the cement within the void did not properly adhere to the pipe and the well bore. Per Terry Barr’s letter, BP didn’t go back and redo the (expensive) cementing job which would be the normal industry standard, despite multiple diagnostic tests, which suggested a problem. They continued.

The next part of the process was to temporarily abandon the well. (I’m not sure what that means or why they did that.) The process involves removing a lot of heavy drilling mud from the well, and replacing it with comparatively low density sea water.

Since the dense drilling mud is used to contain any gas or oil, they lost the primary mechanism for controlling the reservoir pressure when the well was being completed. Barr properly notes the BOP is a backup system that never should have to be used.

With only lightweight seawater in place to hold back gas within the casing, the contents pushed their way up to the Deepwater Horizon deck. Spark. Explosion.

Consequently, Barr attributes the root cause of the explosion to human error, where BP CEO Tony Haward suggests we need better safety technology, pointing to the BOP failure (which is another post in itself) and does not mention the human errors that started well before the explosion on Deepwater Horizon.

Dan P. sums up…

[We must] emphasize the impracticality of converting to 100 percent green energy technology at this time. With the exception of some of the oldest cities in the USA, the infrastructures of all the major and minor cities have been built around the use of the automobile.

Although public transportation is desireable, our businesses and places of work are too decentralized to take advantage of public transportation. How many people are willing to lug their briefcases a couple miles from the primary traffic arteries?

Natural gas is plentiful, but there are very few places where one can go for a quick refill. Also, where can one go to get their batteries recharged if they’ve got an all electric car? (Who would pay the electric bill to recharge your car while you’re in the office or going shopping?)

Solar power is good for small applications, but still impractical for industrial applications. Wind farms are good for supplemental power loads – when the wind is blowing – but is not sufficiently dependable to meet the primary base loads for power demand. (How much efficiency will the windmills loose when they are “bird-proofed?”)

Indeed, we need new sources of energy, but it will take time to develop technologies and help them mature to the point where they become commercially viable options. As such, we must still rely upon oil and natural gas resources for not only fuel for transportation or power, but also as a feedstock for our petrochemical industry and all the chemical products we commonly use, but don’t recognize as having come from natural gas and crude oil.

6 replies
  1. Dimsdale
    Dimsdale says:

    This would have been so trivial to fix in shallow water; more easily accessed and easier to contain.

     

    Thank you greenies!  (you have to wonder if this is the kind of thing they wanted to happen….)

  2. PatRiot
    PatRiot says:

    Great stuff.

    Next step – How much food will NOT be coming out of the gulf?  How will we replace it?  Hint – Don't expect a D&*^ thing from the government.

    Now we find out whom is responsible and sefl sufficient and who is not.

    Though you may not raise up to the ocassion, the ocassion may cause you to raise up.

    We no longer have the luxury of being observers.  We must now be doers or be doomed to something less than we are capable of and what our forefathers sacrificed for. We are in the crucible now, this melting pot called America.  Strong metal is forged best with history's teachings and clear thinking.  Shaped on the anvil of principle with the hammer of conviction.  Or become slag, brittle cast borne of compromise and complacency.

  3. CT-Amy
    CT-Amy says:

    I came across the following survey on-line, and if really defines why I am so confused as to who is 'at fault' in the BP disaster. There is no clear answer.

    Whom do you blame most for the on-going Gulf of Mexico oil spill disaster?

    1. No one is to blame

    2. BP – lessor of the oil rig

    3. Halliburton – contractor, responsible for final cementing of the oil well

    4. Transocean – majority owner of the oil rig

    5. Andarko Petroleum – minority owner of the oil rig

    6. Cameron International – supplier of the failed blow-out preventer

    7. The Government generally

    8. The Obama Administration generally

    9. The Minerals Management Service – government regulator of off-shore oil rigs

  4. Steve McGough
    Steve McGough says:

    Do take a few minutes to read Barr's letter in the Wall Street Journal in response to the BP CEO's Op Ed. The timeline – which was part of a Senate hearing I think – seems to show the"red flags" and lists decisions that were made. Specifically, continuing to replace the heavy mud with lighter sea water that could not hold back the gas pressure. I would expect those decisions were made on-site, on the rig, by engineers working at the time.

    I would not think they make a phone call to HQ – or the federal government – during every step of the process and ask them what to do. I would assume they have authority on-site, as the "expert" on the rig.

    That said, there may have been undue pressure from management off-site to get things done on time and under budget. That does not mean someone off-site was calling and demanding they do something specific.

    It could have been a business culture thing, where the managing engineer on-site – or whoever was making decisions on the rig – was concerned that if he did do the expensive redo of the cement job, he'd be called to the woodshed by upper management for spending a bunch of money. He'd have to justify why he did it.

    Speculation aside, this may have been simply a case of an engineer or two who screwed up and caused a big mess. Blaming a big corporation or the federal government certainly feels good, but that certainly is not always the case.

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