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Sunday, May 30, 2010

Top kill wont stop Gulf of Mexico oil spill

The BP Gulf of Mexico oil spill is perhaps the worst environmental disaster of the 21st century but it also underscores the need for some creative thinking to solve this dilemma.

The problem is a 21 inch pipe or “riser” which has sheared off and fallen like a limp noodle on the sea floor 1500 meters or almost a mile down. The riser is still connected by a flange to the wellhead, but there is a huge open crack in the riser just above the flange. Oil and gas pours from this crack, and, to a lesser extent, from the open end of the broken riser lying on the sea floor.

What surprises me is the wellhead, which appears to be intact and fully operational, appears to have no valves built into it to shut off the flow of oil. Given the real possibility that the pipe or riser could shear off, you would think that every underwater wellhead would have this capability.

The first attempt to stem the leak involved a huge containment structure being dropped over the broken end of the riser sitting on the sea floor. The containment structure included a new riser which could suck up the leaking oil and gas through its domed top. This containment structure failed because of gas hydrate ice crystals blocking its oil riser recovery pipes.

Next a method called “Top Kill” was used to seal the leak on top of the wellhead. In this method a couple of 3” hoses were connected to the wellhead. The hoses were connected at the other end to a special manifold. The manifold could pump thick mud through the hoses from a riser connected to a supply ship on the surface. It also could pump “Junk” or bits of rope, golf balls and other assorted garbage as a means of clogging the open crack at the top of the wellhead.

Top Kill failed presumably because it the pressure was so great that the “Junk” and mud were just blasted through the open crack and nothing managed to gum up the well head enough to stem the flow.

The next solution involves using remote controlled vehicles to operate a shear, to pinch off the end of the riser lying on the sea floor. Another robot submarine will use a diamond wire cutter which will sit on the flange on top of the well head and neatly cut off the riser just above the flange.

Once the riser is cut off, a giant “bottlecap” device will be lowered onto the cleanly cut pipe stub while the oil and gas pours out through the open wellhead under intense pressure. To combat the formation of gas hydrate crystals again, the “bottlecap has a methane injection system.

The real problem is going to be stabilizing the bottlecap while the oil is pouring out. Its like trying to stuff a cork into a running firehose. The power of the flowing oil is going to shove the bottlecap away every time the robots try to position it. The remote control submarines dont have anywhere near the power to hold the cap in place and secure it.

This problem is hard enough to imagine solving a mile beneath the sea, with unimaginable pressures to deal with. My own idea would be to fabricate a steel lance with rubber bladders attached to it. Sort of a giant foley catheter if you will. The lance would be pushed into the open wellhead after the riser had been cut off.

The lance might be easier to push into the wellhead against the pressure of the oil. Once the lance was pushed into the wellhead deep enough, a clamp would secure it against the existing wellhead flange and the bladders would be inflated with hydraulic cement pumped from the surface until the wellhead pipe was completely sealed.

I dont know if my idea would work, but it seems easier to implement given the enviroment a mile below the ocean surface. Hopefully the engineers at BP can come up with a solution quickly, as the scope of this disaster increases with each passing day. And who knows what new problems will surface as long as oil continues to gush into the Gulf of Mexico.

1 Comments:

  • At 8:08 PM, Blogger David said…

    Good comments and a good understanding of the problem. Does anyone have a model of the pieces to play with?

    It seems that if you could string it like a catheter and then clamp the catheter shut it might work. As you say putting a nozzle on a fire hose.

     

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