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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

Views: 14336

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Replies to This Discussion

Okay, I can give a better serious answer.
There's two plausible scenarios for where the cement went. If the casing was substantially intact, the cement went partly out the open hole section and some is left standing inside the casing above that. The amount of holes in the long run of open hole casing is going to make it like an open ended pipe as the collective drainage effect, so all those open holes added together is collectively the one biggest hole below 17,168 feet. Logically, then everything going down that well from the top, even following different paths will be ending up there in the "main drain field" of the open hole casing and the couple of inches between the outside of it and the bored rock. An alternative scenario would be if the casing separated somewhere in the reserve and a cavern was eroded around the break. But there would be a changing flow rate periodically ejecting a lot of gravel and sand on a blowout to evidence that kind of issue, and that was not seen to a great extent when the well was flowing. It was a relatively clean flow. Also if there was such a cavern, the cement would have poured into it and the static kill would not have worked. So logically, and supported also by the pumping data during the static kill, the cement most probably did go down a substantially intact casing and out through the open holes, as they were hoping it would do.
. . . The amount of holes in the long run of open hole casing. . . .

What holes??? There were no perforations or other holes in the original casing. Nobody knows what the condition is now. There could be anything from completely intact to badly damaged. Your scenario seems to be based on the existence of perforations or breaks in the long string.

Mebbe, mebbe not.
Gene----Keith is our science experiment......he keeps us thinking....let's not alienate him.....I need his original thought processes.....

"If it was easy, there wouldn't be any money in it"......

D
With all due respect to the esteemed expertise of Adm. Allen, the highly paid Counsels for BP and Transocean, and eloquent theorists at large...I get the feeling that the DOE is still calling the shots from behind the curtain.


This isn't the first time that Dr. No has chimed-in at the last minute with an extra note of caution.
Keith, all I have is the pipe data in Excel and the Halliburton diagram. The 9 7/8" production casing was standard 62.8 lb/ft 8.625" id crossing over to 7" 32 lb/ft 6.094 id. (no holes except at the shoe). This is I understand how it was going to be left and temporarily abandoned. Another rig was going to come in and do further work to bring it into production. All I can go on is what I can see and not attempting to explain why it was done this way and what they would do in the future (if I am correct in what I can see from the info. available to me). Even if there were a few holes here and there, as I have said before it will not affect too much how they will progress and do not see any point in speculating about it. The only reason I have got drawn back into the discussion is a curiosity that you may have more details of the "production string" that we do not.
Keith, for some reason I missed what you said 6 hrs ago which was basically accepting what I have said bottom of page 69. Thought about deleting it but have left it.
John, I have no information on that final string other than some Halliburton cementing diagrams which are first showing mild gas flow problems and then upgraded that to severe gas flow problems being experienced just before the blowout. That was reenforcing my idea they had a perforated string there below 17,168 feet. I was misunderstanding it looking at the schematic which didn't accurately show the borehole reduction to 9 7/8 at 17,168 feet. Not to mince numbers, but even that "open hole" figure can't be precisely correct because you can't put a 9 7/8 OD casing in a 9 7/8 ID borehole, it would need to be slightly larger than exactly 9 7/8 for the borehole to be a slide fit. But knowing now it is solid walled production casing below 17,168 feet, doesn't change other things much. It still looks like a relief well would have to intersect at a much more shallow depth to be able to inject more cement without breaking loose cement already there above or below. Or the relief well would have to go deeper if the idea was to actually inject cement into the formation, which would seem to be the only place it could go.
The hole that was drilled to set the 9 7/8" liner would be wider as you say (12 1/4"?). I don't know why the hole below the shoe is 9 7/8" to 18,130 ft. Holes can be widened using an under-reamer. In this instance the tool can go down the 9 7/8" liner and mud flow opens up the cutters to the diameter they require (a pilot hole such as 8 1/2" already drilled). I don't know if that was done and why either. Somebody else would have to answer that.
I had an idea that the well was mechanically absolutely finished, ready to go into production, having a sort of "wellpoint" screen / sand filter already in place and was plugged off above with a removable packer or plug , with redundant barriers above. I didn't realize they would put so much effort into drilling a beautiful clean borehole into a reserve and then cement it shut, until another "finisher" rig came along later to undo all the things needed to try to "unshut" the well by perforating the casing, fracturing the cement, and / or drilling out the cement bottom plug, to get the well flowing for production. That seems like a whole lot of extra work being made for later, that would be easier to do going in the first time, leaving the flow shutoff above with something like the supply tap in the cabinet under a lavatory. Is that a regulatory requirement that makes them have to do it that way, basically to cement kill a brand new well rather than to just finish it with a production wellpoint and then plug it off and cap it off topside ?
Sorry, I have not worked at the level where I would have experience of the ins and outs of these things. It may have been something simple like the rig had to go off somewhere else and they did not need a rig of that spec. to finish the work.
The Macondo Prospect is simply that - a "prospect". There are no production facilities available to produce a single well at that depth. BP needs to define the "size of the container". In other words "how big is the prospect and what type/size of facilities" should be installed. At some point later, after several wells have been drilled, a completion program will be developed and completion rigs moved in to complete the project. But only after production facilities have been installed. This is most likely the first of several wells to be drilled at this site.
BK
Keith-This well would have had to be perferated and fraced with another smaller rig before production. IMO

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