Tag Archives: pressure

Deepwater Horizon: what went wrong? They didn’t plug the fucking well, so it blew up.

I’m going to try to keep this brief. I just spent, oh, 3 or 4 hours reading up on the disaster (actually, I’m lying, it’s probably double that), and I think it’s pretty clear what happened. It’d be easy to go on and on about it, but I’ll try to avoid that.

deepwater horizon rig

They were working on a well that they drilled, found their expected oil, and decided to shut it down in order to return to it later. They were capping it, getting ready to leave it behind, when it blew up. They had a violent, catastrophic ‘blowout’ that killed 11 people, their remains never recovered, and the well continues to gush something like 5,000 barrels a day out of the sea floor, threatening thousands of miles of American coastline and ecology.

The key to understanding the catastrophe is to realize that the oil, mixed with gases, is 18,000 plus feet down, hot and highly pressurized. Once vented by drilling into it, they had to be careful how they managed it.

Having tapped it and held it in check, they were sealing it. It’s here where the testimony between the three operators differs as to what they did, and who was responsible for the explosion.

British Petroleum has the rights to the oil, so they own the well on the sea floor. Transocean ran the giant floating rig, now dead. Halliburton were the hands-on contractors doing most of the work. In testimony Tuesday, they all blamed each other. What I believe is clear is this: they never properly ‘capped’ the well. [see diagram here]

The ‘capping’ of a well is a tricky thing, having to make the transition between having a constant, dynamic control of the situation and sealing it off, leaving it behind. With so much pressure in the well, the deepwater horizon rig fireimportant thing was to keep the thousands of feet of heavy ‘drilling mud‘ in the riser (‘pipe’) above the well in the line. Everybody recognizes that. It’s what pushes back on the considerable pressure in the well.

The typical capping procedure appears to go like this:

1.) Cement the upper well area between the drilled rock and outer edges of the metallic well lining to provide a gas-and-oil tight seal.

2.) Drop a cement plug deep into the bore hole, above the oil.

3.) Drop a 2nd cement plug above the first, separated by some amount of drilling mud.

4.) Wait some amount of time to allow the cement to seal and to allow some testing of the ‘cap.’

5.) If assured of the seal, pump salt water into the riser to extract the drilling mud. The well is capped.

We know this: they were capping the well. But someone ordered the heavy drilling mud removed before the cap was properly set. At least one and maybe both cement caps were never set, but they began to back off the well anyways. With minimal ceiling pressure, the gases exploded out of the well and then ignited only a minute or two later, killing 11 people, sealing the fate of the rig and the Gulf of Mexico.