Thursday, June 3, 2010

Deepwater Oil Spill - capping the riser - Part 1

The vertical section of the riser was cut, using a Shear at 9 am this morning.

Lower Riser Assembly (LRA) atop the Blowout Preventer (BOP) at the Deepwater Horizon well, with the bent riser removed, waiting for the arrival of the Lower Marine Riser package (LMRP) The oil and gas are rising vertically, from the top of the riser, the drill pipe (DP) and the saw cut in the side of the riser (just down from the top of the shear).

At 8:30 pm the ROVs maneuvered the latest version of the “top hat”, variation 7, of the LMRP over the top of the LRA. As the new cap was lowered into place it was surrounded by clouds of oil and gas, making the actual progress of the event somewhat difficult to follow. The new variation had been finished yesterday, to accommodate the changing upper surface of the remnants of the well.

Building LMRP 7 on June 2nd at Port Fourchon (BP )

The Lower Marine Riser Package (LMRP) was first connected to the riser, an to a methanol feed that would help, between them, to inhibit the formation of methane hydrides when the gas came into contact with the surrounding cold seawater. It was then slowly lowered to the site. (You can see the seal, referred to later, along the bottom edge - h/t KLR).

Interior of the LMRP as it was lowered. (KLR)

Once it reached the right depth it was moved across into the fountain of oil and gas, and down over the top of the riser.

Lowering the LMRP into the cloud of oil from the riser.

The initial attempt halted after a while, and by 9 pm the situation was, for while static. The cap was sitting apparently on the rubber seal that had been designed to fit between the LMRP and the flange, but the amount of oil that was leaking out of the bottom of the LMRP, was still a considerable amount, even though some of the flow was also being bypassed through ports on the LMRP that could later be closed.

Flow through a relief port on side off the LMRP to relieve the pressure within it.

Leakage around the seal between LMRP 7 (yellow), the seal (greenish black) and the LRA. (white)

The question now arises as to whether the LMRP could be lowered sufficiently that it could seal to the flange surface, since it was no longer possible to get the seal needed on the upper surface of the riser, given that it had been distorted by the Shear which had cut the bent riser away.

There was a pause, while the engineers had a bit think for over an hour. Looking at the cloud of oil coming out, it does contain small white specs that could be either methane hydrates or drops of the dispersant. And now, at 10:30 pm, there is a little more action.

Oil and gas coming out from under the LMRP

Leaks under the LMRP at 10:30 pm

For those who may not remember, this was the initial plan as it was proposed.

The Lower Marine Riser Package (LMRP) option

So far it is not quite as simple as the sketch would suggest. But I will put this up, and then update, as changes appear. But we may be in for a bit of a wait as they may only slowly close the valves and direct the flow to the surface, as they did with the first oil capture at the RIT. They will be checking slowly through the process to see that as little as possible goes wrong, as they ramp up the flow, and slowly turn off the bypass valves.


  1. wow, you have to imagine the pressure to do something vrs the need to get it right. Its the right part that looks a little weak now.
    Not an enviable position to be in. No matter how worrisome this thing is I'd hope people remain aware of the difficulty. My support goes to the people involved in the effort.
    I'm absolutely livid at the commentators/reporters who lambaste the business's efforts/integrity. Specially those who cede to the government the authority/correctness.

  2. I'm surprised they didn't continue with the diamond saw. They must have thought it would continue to get stuck i suppose, but now they cannot seal onto the riser stub.

    The problem with sealing to the flange is the bolts will foul any seal.

    Its an amazing technical feat working with robots at that depth.

    But i am surprised how much the operators have to do manually (eg. untying sling webbing by robot hand) Theres obviously a real market for quick disconnect technology down there (for rigging) and better tools on the ROVs for the operators: like big rattle guns to get that flange off and seal directly to the top of the LMRP. (no need for cutting and should be a nicer seal) Obviously there might be technical and power limitations but i'm surprised how manual it is.