Tuesday, June 1, 2010

Deepwater Oil Spill - cutting the Riser

At present they have started cutting through the pipes around the riser. At 8:45 am they had the shearing machine set on the riser and then just after 9:am they brought in a circular diamond saw that is now cutting through the choke and kill lines that are running beside the riser. Part of the problem they face is that they don't want to cut into the riser pipe directly behind the current pipe, because that would flood the viewing area with spurting oil and gas. And at 10:05 am they got through it.

10:04 am just before the pipe was severed.

10:10 am Overview

10:30 am Wire saw on riser

11:05 am Given the shift in the source of the oil, I suspect they are shearing the riser, but have backed the ROVs away to ensure they don't get damaged, so the view is somewhat unclear.

1:00 pm They had moved the shearer upstream along the riser to try and make a second cut. This time including the choke and kill lines. Not sure why, perhaps there was a joint in the drill pipe at the first site and they could not get all the way through. However they started to shear at this second location, backed off, and then at about 12:45 pm starting in again.

1:15 pm I had stepped away from the computer for a few minutes, and came back to a screen full of oil, so initially I thought that the shearer had cut through the riser, but apparently just about 12:50 pm the shearer released the pipe, and was hoisted off, perhaps to the surface for evaluation, or replacement or repair. We'll have to wait to find out.

Before the wire saw was put in place on the Lower Riser Assembly (LRA) I took a couple of screen shots to show a) how much stress the BOP may still be under, since the whole frame is tilted in the direction of the riser:

And then this is where the wire saw will be cutting, and it shows how much the riser was deformed.

I'll add more to this post over the course of day as the cutting continues.


  1. Instead of cutting it, why not simply unbolt the flange and put a gate valve on the flange, bolt it up then close the valve? wouldn't that be so much simpler? or is there production tubing inside the riser too?

  2. Too much bending torque on the riser to be sure that it would work.

  3. Can you explain that a bit more please? With nearly all the riser removed, why is there so much torque?

    I wondered whether the bend on the BOP might indicate it's weakened?

  4. The most logical approach might be to cut the ends off the bolts, but the differential pressure across the riser might still bind the body of the bolt with a problem them of a potential untimely or uncontrolled release, which could be quite dangerous.