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Transocean Deepwater Horizon Explosion-A Discussion of What Actually Happened?

 I will start the discussion with this which came in email a moment ago...

Anybody with any thoughts?


April 26, 2010       Transocean
Rig Disaster: The Well From Hell

Once more unto the breach, dear friends, once more. Here's another update on the disaster that befell Transocean Ltd. and BP last week in the Gulf of Mexico.
(Thanks to OI reader Steve, in Texas, for sending some of the photos in today’s alert.)

As you know by now, the drilling vessel Deepwater Horizon exploded, burned and sank last week, with the loss of 11 workers and injuries to many more. What happened? What's happening now? What's going to happen? I've spent the weekend working to piece things together.

An Ill-fated Discovery
According to news accounts, at about 10 p.m. CDT last Tuesday, Deepwater Horizon was stable, holding an exact position in calm, dark seas about 45 miles south of the Louisiana coastline. Water depth in the area is 5,000 feet. The vessel manifest listed 126 souls on board.

Deepwater Horizon was finishing work on an exploration well named Macondo, in an area called Mississippi Canyon Block 252. After weeks of drilling, the rig had pushed a bit down over 18,000 feet, into an oil-bearing zone. The Transocean and BP personnel were installing casing in the well. BP was going to seal things up, and then go off and figure out how to produce the oil -- another step entirely in the oil biz.

The Macondo Block 252 reservoir may hold as much as 100 million barrels. That's not as large as other recent oil strikes in the Gulf, but BP management was still pleased. Success is success --
certainly in the risky, deep-water oil environment. The front office of BP Exploration was preparing a press release to announce a "commercial" oil discovery.

This kind of exploration success was par for the course for Deepwater Horizon. A year ago, the vessel set a record at another site in the Gulf, drilling a well just over 35,000 feet and discovering the 3 billion barrel Tiber deposit for BP. SoDeepwater Horizon was a great rig, with a great crew and a superb record. You might even say that is was lucky.

But perhaps some things tempt the Gods. Some actions may invite ill fate. Because suddenly, the wild and wasteful ocean struck with a bolt from the deep.

The Lights Went out;
and Then.
.. 

Witnesses state that the lights flickered on the Deepwater Horizon. Then a massive thud shook the vessel, followed by another strong vibration. Transocean employee Jim Ingram, a seasoned
offshore worker, told the U.K. Times that he was preparing for bed after working a 12-hour shift. "On the second [thud]," said Mr. Ingram, "we knew something was wrong." Indeed, something was very wrong.

Within a moment, a gigantic blast of gas, oil and drilling mud roared up through three miles of down-hole pipe and subsea risers. The fluids burst through the rig floor and ripped up into the gigantic draw-works. Something sparked. The hydrocarbons ignited. In a fraction of a second, the drilling deck of the Deepwater Horizon exploded into a fireball. The scene was an utter conflagration.

Transocean Deepwater Horizon Listing

Evacuate and Abandon
Ship 


There was almost no time to react. Emergency beacons blared. Battery-powered lighting switched on throughout the vessel. Crew members ran to evacuation stations. The order came to abandon ship.
Then from the worst of circumstances came the finest, noblest elements of human behavior. Everyone on the vessel has been through extensive safety training. They knew what to do. Most crew members climbed into covered lifeboats. Other crew members quickly winched the boats, with their shipmates, down to the water. Then those who stayed behind rapidly evacuated in other designated emergency craft.

Some of the crew, however, were trapped in odd parts of the massive vessel, which measures 396 feet by 256 feet -- a bit less than the size of two football fields laid side by side.( This is one big
Drill Ship) They couldn't get to the boats. So they did what they had to do, which for some meant jumping -- and those jumpers did not fare so well. Several men broke bones due to the impact of their 80-foot drop to the sea. Still, it beat burning.

With searchlights providing illumination, as well as the eerie light from the flames of the raging fire, boat handlers pulled colleagues out of the water beneath the burning rig. In some instances, the plastic fittings on the lifeboats melted from the heat.

The flames intensified.
Soon it was impossible for the lifeboats to function near the massive vessel. The small boats moved away from the raging fountain of fire fed by ancient oil and gas from far below.

Transocean Horizon Burning At Night

The lifeboat skippers saved as many as they could find -- 115 -- but couldn't account for 11 workers who were, apparently, on or around the drill deck at the time of the first explosion. Nine of the missing are Transocean employees. Two others work for subcontractors.

Damon
Bankston to the Rescue 


Fate was not entirely cruel that night. Indeed, a supply boat was already en route to the Deepwater
Horizon. It was the Tidewater Damon Bankston, a 260-foot long flat-deck supply vessel.

Damon Bankston heard the distress signal. Her captain did what great captains do. He aimed the bow toward the position of Deepwater Horizon. Then he tore through the water, moved along by four mighty Caterpillar engines rated at 10,200 horsepower. Soon, the Damon Bankston arrived on scene,
sailed straight into the flames and joined the rescue.

Meanwhile, Coast Guard helicopters lifted off from pads in southern Louisiana, and Coast Guard
rescue vessels left their moorings. "You have to go out," is the old Coast Guard saying. "You don't have to come back."

The helicopters flew in the black of night toward a vista of utter disaster. Arriving on scene, the pilots watched in awe as columns of flame shot as high as a 50-story building. The helicopters were buffeted by blasts of super-heated wind coming from the flames, while chunks of soot the size of your hand blew by.

The pilots hovered in the glow of the blazing rig, while Coast Guard medics fast-roped down to the deck of Damon Bankston . The medics quickly assessed the casualties, strapped critically injured crewmen to backboards and hoisted them up to the helicopters. Then the pilots turned north and sped ashore to hospitals.

Uninjured survivors returned to land on the Damon Bankston. And others came out to fight
the blistering flames.

But the Deepwater Horizon wasn't going to make it. The situation deteriorated, to the point of complete catastrophe. The ship was lost.

Transocean Horizon On Fire Sinking

At about 10 a.m. CDT on Thursday morning, 36 hours after the first explosion, the Deepwater Horizon capsized and sank in 5,000 feet of water. According to BP, the hulk is located on the
seafloor, upside-down, about 1,500 feet away from the Macondo well it drilled.

Still Spilling Oil 
On Friday, I told you that the oil well drilled by the Deepwater Horizon was sealed in. The "official" word was that the well wasn't gushing oil into the sea. My sources were no less than U.S. Coast Guard Rear Adm. Mary Landry, of the New Orleans district, as quoted in The New York Times. 

But over the weekend, Rear Adm. Landry and The New York Times reported that the well IS leaking oil, at a rate of about 1,000 barrels per day.

The on-scene information comes from remotely operated underwater robots that BP and Transocean are using to monitor the well and survey all the other wreckage of the Deepwater Horizon. There's now a large amount of equipment and pipe and a myriad of marine debris on the seafloor near the well. It's a mess.

Apparently, the blowout preventer is not controlling the flow of oil. According to Transocean, the blowout preventer on Deepwater Horizon was manufactured by Cameron Intl. (CAM: NYSE). 

What happened? We don't know that just yet. Earlier reports that underwater robots sealed the blowout preventer were wrong. It's possible that the blowout preventer is only partially closed. We'll find out, eventually. Meanwhile, BP and Transocean have announced that they will make another effort to activate the blowout preventer. They need to stop that oil.

BP is also preparing to drill one or more relief wells to secure the site permanently. BP has mobilized the drilling rig Development Driller III, which is moving into position to drill a second well to intercept the leaking well. With the new well, the drillers will inject a specialized heavy fluid into the original well. This fluid will secure and block the flow of oil or gas and allow BP to permanently seal the first well.

Riser Problems? 

According to the Coast Guard and BP, oil is leaking from two spots along what is left of the riser system. Here's a schematic view:

Transocean Horizon Sea Floor Diagram

Originally, the risers (represented by the blue line in the graphic above) were affixed to the blowout preventer on the seafloor, and extended 5,000 feet straight up to the "moon pool" of the Deepwater Horizon. When the drilling vessel sank, it took the riser piping and bent it around like a pretzel.

The remnants of the riser system now follow a circuitous underwater route. According to BP, the risers extend from the wellhead up through the water column to about 1,500 feet above the seabed.
Then the riser system buckles back down toward the seafloor. (Frankly, I'm astonished that it all held together as well as it has. It's a credit to the manufacturer, which I'll discuss below.)

According to the Transocean website, the riser devices on the Deepwater Horizonwere manufactured by VetcoGray, a division of General Electric Oil & Gas. The specific designation is a "HMF-Class H, 21-inch outside diameter riser; 90 foot long joints with Choke & Kill, and booster and hydraulic  supply lines."

Here's a photo of something similar. These are Vetco risers sections that I saw on another vessel, the Transocean Discoverer Inspiration, when I visited that ship last month:

Transocean Horizon Riser Sections

The different color stripes on the risers indicate differing amounts of buoyancy. The idea is to put heavy riser pipe down at the bottom, connected to more buoyant risers above. The buoyancy
keeps the entire riser system in more or less neutral buoyancy, so that the drill ship doesn't have to somehow hoist up the huge weight of all that pipe.

As you can see, there's a large-diameter pipe in the middle of each riser. That pipe is then encased in a buoyant foam substance. The risers are bolted together at the flange sections. The bolts are about as big as the arm of a very strong man. The nuts, which tighten things down, are the size of paint cans.

After the risers are assembled and hanging down from the drilling vessel, the drilling personnel lower and raise drilling pipe through the large-diameter center riser pipe. All the drilling mud stays inside the drill pipe on the way down hole, and inside the riser pipe on the return.

On the side of the riser sections, you can see smaller-diameter pipes. These are choke & kill, booster and hydraulic pipe components. The pipes run parallel to the large-diameter inner pipe. These pipe systems run down to the blowout preventer on the seafloor.

The idea is to keep the drilling process an enclosed system. All the "drilling stuff" -- the drill-pipe, drilling-mud and drill-cutting returns -- stays inside the large-diameter pipe. The smaller pipes
hold fluid to transmit hydraulic power and help control drilling. In particular, the pipes on the side aid in communicating with and controlling the blowout preventer.

Technical Specs 

Ideally, when the risers are working as intended, nothing leaks out into the sea. Then again, you're not supposed to twist and bend the riser sections like a pretzel. So how strong is a riser
system? Extremely strong, actually.

According to technical literature from GE Oil & Gas, the riser equipment is "designed for use in
high-pressure, critical service and deep-water drilling and production applications." The pressure-containing components are rated for working pressures of 15,000 psi. That's the same as the Cameron blowout preventer on the Deepwater Horizon. The materials used in risers have
exceptional tensile and bending load characteristics.

According to Vetco paperwork that I've seen, the Class H riser sections have a 3.5 million pound
load-carrying capacity. That's the equivalent weight of about four fully fueled
Boeing 747s. These risers are super strong.

Still, it's not just any one single piece of riser section that does it all. These sections all get bolted
together, for 5,000 feet in this case. The riser sections all have to work together as a system. The whole string is only as strong as the weakest spot. And yes, even the strongest steel will break if you apply enough stress.

It all has to work together. You've got the riser sections, along with things called HMF flanged riser connectors. Then there are HMF riser joints; flex joints; telescopic joints; and, near the top, things called "fluid-bearing, nonintegral tensioner rings." Together, these all comprise the marine riser system.

In general, the riser components compensate for heave, surge, sway, offset and torque of the drilling vessel as the ship bounces around on the sea surface. The bottom line is to maintain a tight seal -- what's called "integrity" -- between the subsea blowout preventer stack and the surface
during drilling operations.

Down at the bottom, at the seafloor, the risers are connected to the blowout preventer by a connector device. The GE-Vetco spec is for a device that accommodates 7 million foot-pounds of bending
load capacity. That's about eight fully fueled Boeing 747s.

What's the idea? You want a secure connection between the high-pressure wellhead system and
the subsea blowout preventer stack. That's where mankind's best steel meets Mother Nature's high pressures.

High pressures? You had better believe it. And in this case, Mother Nature won. So looking forward, there's going to be a lot of forensic engineering on the well design and how things got monitored
during drilling. Transocean drilled the well, but BP designed it. So the key question is how did the down-hole pressures get away like they did?

What Happens
Now? 


It's a good thing that the Deepwater Horizon didn't settle right on top of the well. At least there's room for the remotely operated vehicles to maneuver. Also, there's still a lot of riser still floating in the water column. So there's some element of integrity going down to the blowout preventer.

It's absolutely imperative to shut off that oil flow. We just have to hope and pray that the BP and Transocean people can get the blowout preventer shut off. Or that there's enough integrity to the risers somehow to get in there and control the leaks, perhaps with some sort of plug. One other idea is to lower a large "hood" over the leak and capture the oil so it can be pumped up to a storage tanker ship.

Meanwhile, the relief well has to go down -- carefully and safely. This Macondo well is history. Seal it. Mark it. Give it back to the sea. Move on. Don't tempt fate on this
one. And wow... for a relatively modest-sized deep-water discovery, this
thing sure has turned into the well from hell.

Welcome to the World of Deep-water Risk 

As I've said before, this accident is Mother Nature's wake-up call to everyone. Deep-water drilling is a high-stakes game. It's not exactly a "casino," in that there's a heck of a lot of settled science,
engineering and technology involved.  But we're sure finding out the hard way what all the risks are. And it's becoming more and more clear how the totality of risk is a moving target. There's geologic risk, technical risk, engineering risk, environmental risk, capital risk and market risk.


With each deep well, these risks all come together over one very tiny spot at the bottom of the ocean. So for all the oil that's out there under deep water -- and it's a lot -- the long-term calculus of risk and return is difficult to quantify.

There's more to discuss, but I'll end here today. I'll update you as things evolve. This is big news all through the offshore industry. There are HUGE environmental issues, and certainly big political repercussions. I won't go there just now. For now, I'll just send out collective best wishes to the people at Transocean, BP, the Coast Guard, Minerals Management and so many more. I'm sure they're doing their best.

Thanks for reading...

(Name Withheld)

Tags: Transocean, cause, deepwater, discussion, explosion, happened, horizon, what

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Replies to This Discussion

I cannot see the point of speculating on how this well is abandoned. Kent Wells says that they want to see what is in the annulus. They may pump some more cement via the relief well depending on what they see and circumstances allow. I don't know how much cement in the annulus is required. As Ken says, the relief wells can be sidetracked and MC 252 intersected higher up if it is really necessary to carry this out. I am not saying there will be no problems (there is perhaps a bit of vulnerability if they swop the BOP's but they must have all thought it through). If they have the new BOP installed and the drillpipe recovered, they can then work on MC 252 directly just like any other well and go through the abandonment program. They will I believe, also cut and recover some of the production casing. After this, any plugs that are set above, will include what we are presently calling the annulus. Anticipation of this should minimise the work the relief wells need to do. That's my two cents. I am a fluids man and have never planned or supervised drilling a well. I agree with Deeper, BP have assembled the best people in the world in addition to their own.
I thought I deleted this post. Oh Well it's been out there all day.
They may have been able to tell the difference between cement going down the inside of the casing or down the annulus of the 7" as the annulus is so small and the cement heavy.
If they are planning to work on this well from the top down there may not be cement to surface. maybe no cement above the bottom of the drill pipe.
Keith,

From the get-go the RW was planned to intersect below the 9 7/8 casing shoe and above the original planned TOC for the final long string. If everything had gone as planned that area would have nothing but an annulus between the rock and the final string. No cement or other steel. Of course there might be loose rock or other debris. Supposedly the final Macondo cement job was set at 51 barrels in order to keep the TOC below the 9 7/8 casing.

I don't claim even the slightest bit of wisdom in any of these choices, and I have no idea what the current condition really is. However, I am pretty sure that everything I have read supports my comment.

You seem to have a very different picture of the well configuration and the RW strategy. Perhaps that is why you are not getting any responses.
Gene, Yeah I understand about what was the plan earlier, (before the static kill) however, the situation now is a different story. On the page before I was asking for information about the open hole section of 9 7/8 which is #45 on the xls document that Ken was referencing. Cement being pumped down from the top, (and not exiting from the end of a drill pipe during a static kill)
should flow out of those holes and it would likely be going out of those holes first where they start, which is 17,168 feet . Maybe the schematic is wrong, because I do not understand the wisdom of that design either. It would have seemed to me that the there should have already been cement around the outside of the upper part of the open hole 9 7/8 liner from when the end of that outer 10 5/8 X 12 1/4 casing was cemented, and that whole area there should have been cemented before proceeding with the open hole production liner into the reserve below. But that isn't what the schematic shows. The schematic doesn't show that area being cemented but only having mud there. Is the schematic wrong ?
Has anyone seen or heard anything said about a radioactive tracer being pumped in the cement/mud used in the top kill a couple of weeks ago?

I don't know if the relief well is close enough to the Macondo to swap fluids and thereby be able to log radioactive tracers....just a thought....

D
Keith, it would appear from line 45 of the table you are talking about, there was below the 9 7/8" liner shoe at 17,168 ft, 9 7/8" hole from 17,168 ft to 18,130 ft (under-reamed?) and 8 1/2" hole from 18,130 ft to TD, 18,360 ft. For the purpose of what we are talking about it does not make a lot of difference what size hole it is (although it would of course when planning the cement job). What is at issue was how much cement was in this annulus with the 7" production casing when the casing was initially cemented and what is in the annulus now after the last cement job.

The 9 7/8" liner is cemented. The 11 7/8" liner is cemented. The 13 5/8" liner is cemented and the 16" intermediate casing is cemented.

I cannot see what bearing all of this has on what they are doing now.
John, with regards to the cementing of the 9 7/8 open hole casing below 17,168 feet , I agree it is cemented there now. The strategy for the relief well was based upon the premise that the intersected section could only be cemented from the bottom up by the relief well. The premise for that strategy in all likelihood no longer exists. There was greater likelihood during a static kill of getting cement into the annulus area there at 17,168 feet via the cement going out through the open holes of the 9 7/8 because the 9 7/8 is on location there, compared to the relief well intersection over 700 feet below. The chance for the relief well to accomplish better cementing from that distance below is pretty far fetched. The relief well effort is more likely to disrupt the patch / plug that is presently there than to reenforce it. A bird in the hand is worth two in the bush. And the relief wells are beating the bushes, when the bird (the killed well) is already in the hand.

There is an old saying, if it aint broke - don't fix it.

That is the bearing which I think it has on the relief wells.

But as far as what they are doing now, with ambient pressure test observations for any leakage, with plans to pull the BOP, there is not really any bearing at all, if that is what you mean.
John, I see what you are talking about now. The "tubular" listed on the xls documnent as 9 7/8 open hole and as 8 1/2 open hole is simply bored hole in the rock and is no perforated steel sleeve section. The schematic doesn't show any reduction in diameter of the borehole below the bottom of the 10 5/8 x 12 1/4 at 17,168 feet until near the very bottom at 18,115 so evidently the schematic is just not showing the stepdown in borehole diameter at 17,168 feet and that is the reference to "open hole" as being stepped down to a 9 7/8 borehole diameter. The schematic just shows a straight dotted line down from the outside of the 10 5/8 X 12 1/4. There is no "screen" nor perforated section in the production zone, just solid walled pipe, with what should have been a solid cement plug in the bottom end, and it would have required drilling out the plug and / or perforating the production casing later and fracturing the cement to let the well flow again when it was resurrected / reworked for production after being temporarily abandoned. So the plug blew completely out of the bottom inside and / or blew past the outside of the production casing too. Obviously the cement forced backwards during the static kill would tend to follow the same flow paths in the reverse direction, unless somehow loose parts were acting like a one way check valve in the upflow direction, but that would have blocked the injectivity of the cement, it would have pinched off from taking the cement with rising pressure very quick. But they say it got a good dose of 500 barrels which evidently got to where it needed to go to stop the inflow. Attached is an image of an old walking beam well with a perforated casing, probably from a few years before perforating guns came along. And attached is another image of where I was thinking the relief well more ought to be if they are going deep, perforated casing matters aside. I still think it is not a good idea to be banging on that metal there where they are, as it could shake loose something that may stay plugged if left alone.
Attachments:
Good thought Deeper.
Go figger...go figger......

If any one person responding to this can tell me with absolute certainty as to where the mud and cement went when they did the top kill.....and can tell me the downhole status of this well.....then I have an invitation for you.............

I will meet you on the beach at Grand Isle, Louisiana next Saturday at 9:00am......wherewith I will listen to your premise. After delivering your premise, and your further explanation of exactly how you determined EXACTLY WHERE all that mud and cement went.......and now further allowing that a Coast Guard mouthpiece who SUDDENLY decided to retire from guv'mint service is now your ONLY source of info....

Dammit I lost my train of thought...here is the gist...and not just to Keith....if ANYONE can tell me where the cement went with 100% equivocal authority, I hereby invite you to meet me on the beach at Grand Isle next Saturday morning so I can publically invite you to kiss my skinny bare white a**.

Put the f++++ing calculators up. Nobody knows whats going on down hole because they can't run tools there.

Deeper......the eloquent theorist.........
With 100% certainty I can say that where the cement went is where the holes are :)
Now how far into those holes and where it is now ......that's a different matter entirely.
Wasn't asking that .......It doesn't take a great scientific and logical mind to make a statement like "it went where the holes are....."

The point is......where are the holes? And do holes really exist? How do you determine where the cement went? They didn't open the new BOP and tie into the existing string......that right there tells you they were able to stuff a bunch of crap down there with no clue as to where it went, only a couple or three options.........Unless they opened the new BOP and tied into the casing or drill pipe....then that crap went where it wanted to go.........and it didn't have a lot of options......(maybe two????)

......go figger...........

D

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