Grim outlook: 2.3m barrel Gulf spill

Monday 31st May 2010
BP's current plan. Courtesy: http://www.theoildrum.com/node/6516

High technology may be great at getting drills to work at 5,000 ft depths. It has been less perfected to close off wells at those depths as the Gulf spill spells out. US Secretary of Energy Steven Chu has told BP that the company should stop the 'top kill' operation, its attempt to plug the well with pressuried driling mud long enough to be able to seal it permanently with cement. Government officials thought it was too dangerous to keep pumping drilling mud into the well because they are worried it was putting too much pressure on it.

In a press release from BP,  The US Government, together with BP, have therefore decided to move to the next step in the subsea operations, the deployment of the Lower Marine Riser Package (LMRP) Cap Containment System.

The operational plan first involves cutting and then removing the damaged riser from the top of the failed Blow-Out Preventer (BOP) to leave a cleanly-cut pipe at the top of the BOP’s LMRP.

The cap is designed to be connected to a riser from the Discoverer Enterprise drillship and placed over the LMRP with the intention of capturing most of the oil and gas flowing from the well. The LMRP cap is already on site and it is currently anticipated that it will be connected in about four days.

This operation (again)  has not been previously carried out in 5,000 ft of water and the successful deployment of the containment system cannot be assured.

Drilling of the first relief well continues and is currently at 12,090 feet. Drilling of the second relief well is temporarily suspended and is expected to recommence shortly from 8,576 feet.

New York Times reports BP is now working on several containment plans, with the first being implemented over the next few days. “Riser cutting will likely start Monday or Tuesday,” White House press secretary, Robert Gibbs, said in a Saturday statement.

Using ( right) submarine robots, technicians intend to sever the riser pipe on top of the blowout preventer, the five-story-high stack of pipes above the well that failed to shut off the leak when the Deepwater Horizon rig exploded on April 20, killing 11 workers.

A funnel-like containment device will be fitted above the cut riser to draw the escaping oil through tubing attached to a drilling ship. But BP officials acknowledged that there was no certainty that this attempt would work.

Robert Dudley, (left) BP’s MD said that if it did work, some oil would still seep out until relief wells provided “an end point” in August.

The failure of the most recent effort — known as a 'top kill' which BP officials expressed great optimism about before trying it — has underlined the gaps in knowledge and science about the spill and its potential remedies.

[It has also given rise to some cynical definitions of top kill as "a technique used to kill everything on top of the ocean using chemical dispersants so dead animal bodies to sink and can't be caught on camera."]

Ever since the explosion and the resulting leak, estimates of how much oil is escaping have differed by thousands of barrels a day. Both government and BP officials said on Sunday that they had no accurate idea of how much oil was spilling into the gulf.

“We honestly do not know,” said Dudley ” “We’ve always found this a difficult oil to measure because of the huge amounts of gas in the oil. The one thing about this method that we’re about to go into — it will and should measure the majority of the flow,” he said.

Dudley said that the original estimates by the government and BP officials of 5,000 barrels a day were based on satellite pictures and current estimate of 12,000 to 19,000 barrels was “issued without an actual flow measurement.”

If the leak is not contained or slowed and continues at the higher estimated flow rate of 19,000 barrels a day until Aug. 20 — four months after the accident — it could amount to close to 2.3m barrels spilled into the gulf.

After more than a month of diagnostic tests and the pumping of tens of thousands of barrels of drilling fluids — and everything from golf balls to shards of rubber — into the broken blowout preventer, engineers are still debating about what they think may be the inner contours of the five-story stack of pipes and how to best contain its leaking gashes.
(Right: protection booms).

The final plugging of the well has to wait until August, when the two relief wells are scheduled be completed. Those are being drilled diagonally to intersect with the runaway well and inject it with heavy liquids and cement. Work could be slowed by storms in what is expected to be an active summer hurricane season.

Engineers  are once again trying to solve the problem with a containment cap which failed because a slush of icy water and gas, known as hydrates, filled the large containment device, blocking the escaping oil from entering it.

This time, engineers will pump hot sea water around the new, smaller device to keep hydrates from forming, and there will be far less space between the cap and the well for any hydrates that do form to flow in.




BP officials express optimism about the new operation. One technician warned  that hydrates could again stymie effort and by cutting the riser, engineers may increase the flow of escaping oil.

Donald Van Nieuwenhuise, (right) director of petroleum geoscience programs at the University of Houston, said he thought BP’s next plan had a good chance of succeeding, but that there was also a risk of increasing the flow of escaping oil by 10%.

“Then it just makes the situation worse for longer,” he said, unless the containment cap succeeds in collecting a substantial amount of oil.

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