24 May 2010

Top Kill Scheduled for Wednesday; Preparations Video

Oil spill video: BP shows ROVs at work

The video provides a revealing look into ROV operations in the leadup to the Top Kill operation, now scheduled for Wednesday, the 26th of May.
BP will attempt a "top kill" maneuver to permanently stanch the oil flow from a leaking well Wednesday morning and will know whether or not the procedure is working by that evening, the company's Chief Operating Officer Doug Suttles said Monday. If the top kill does not work, the company will try to contain the oil by placing a cap on the riser pipe and sucking oil to the surface.

"This job has taken quite some time to prepare and plan for. It's not unique or new but it is unique and new in 5,000 feet of water," Suttles said. "If that operation is successful, we will be able to stop the flow from the well."

Tony Hayward, BP's chief executive officer said Monday that there is a 60 percent to 70 percent chance of success with the top kill.

The single biggest challenge to the procedure, Suttles said, will be overcoming the rate at which oil is gushing up from the well.

...The top kill will be performed near the smaller of the two leaks. The second, larger leak, has been affixed with a tube that is capturing some, but not all, of the oil and natural gas spilling from it. Because the top kill will be performed at the base of the broken pipe, down near the blowout preventer, it should permanently shut off both leaks if it is successful.

The top kill process involves pumping fabricated "kill mud," which is about twice the density of water, into the well at 50 barrels a minute to overcome the flow.

The material will be pumped at that high pressure down the choke and kill lines of the blowout preventer, which failed to seal the well after the rig exploded, to push the oil back into the reservoir. Choke and kill lines are used to control the amount and pressure of drilling mud in the wellbore so that surges of oil and natural gas can be kept under control.

If the kill mud is not able to overcome the flow of oil, it could get trapped in the riser pipe and erode it, which could lead to additional leaks, Suttles said.

The drill mud could be followed with cement to permanently seal the well.

Should the maneuver fail, BP may pump debris into the well to clog it and then try the top kill again, Suttles said. The company may also cut the joint where the riser pipe comes out of the blowout preventer and place a cap on it. The cap would be attached to another riser pipe that BP would use to suction oil from the well to a drill ship on the surface. Doing so would not stop the flow of oil, but would contain oil escaping from both leak sites. _NOLA
Oil spill trajectory forecast:

WKRG.com News
Live webcam of spill and undersea operations:

Watch live streaming video from wkrg_oil_spill at livestream.com
More 25May10:
The pumps will deliver the mud into the lines at a pressure of 6,800 psi, but as Kinuachdrach has correctly noted, it will then acquire the pressure from the full 5,000 ft column of mud as it flows down to the BOP, and enters the flow channel carrying the oil. Now we know that the BOP rams are at least partially closed. If they are planning on using golf balls for the “junk shot”, it is feasible to surmise that the maximum width of the flow channel is no more than a third of a golf ball diameter. Not arguing the merits of American vs British ball sizes, let us assume that this is roughly half-an-inch (though it may have a greater length).

However, as flow volumes go up it requires more and more pressure for the fluid to get through a small gap. And at a given delivery pressure, only a certain flow volume will thus be able to escape that way. As long as this pressure exceeds that in the well, the net result will then be that the mud begins to push the oil and gas back down the well, and the well fills up with mud. The weight of that mud should then be enough to exert a pressure on the bottom of the well that is enough to exceed the fluid pressure in the rock and therefore stabilize the well and stop the flow of fluid out. Cement can then be pumped into the well to seal the top end. (Or with the flow stopped, another BOP can be put on the well to seal it). The main worry is that the hole in the top of the BOP is small enough to contain the additional flow volumes, and not allow the entire flow to escape upwards rather than being forced down the well. The higher flows might, in addition, if they do exit the riser, further erode the openings. This could increase the oil flow, as it lowers the resistance. (If this happened then the LMRP will be deployed).

Lower Marine Riser Package Fallback Plan
The London-based company said on Tuesday it had plans to remove a damaged part from the ruptured well and put in place a tube which would capture most of the oil and gas flowing into the sea, calling it the LMRP cap containment option.

BP already has one tube in place which is siphoning off an average 40 percent of the 5,000 barrels of oil [NOAA and the USCG] estimates is leaking out of the well each day. [Ed.: a final report from the special committee appointed to assess leak flow is due any time now]

The company said it would be ready to try to fit the new tube by the end of the month, but in the meantime it would attempt in the next few days to plug the leak using heavy fluids -- the so-called "top kill" option that BP has given a 60 to 70 percent chance of success. _Reuters

As noted before, these procedures have not been done at these depths. This disaster has also been an opportunity for deep sea drilling engineers and technicians to study and rank a number of methods to mitigate the damage from such a rare but potentially catastrophic event.

Persons whose property and livelihood were damaged from the spill deserve to be compensated. Ghoulish journalists, academics, activists, and lawyers may more properly deserve to be shot.


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