2010年8月3日火曜日

Methods That Have Been Tried to Stop the Leaking Oil : The New York Times

【出展リンク】:

http://www.nytimes.com/interactive/2010/05/25/us/20100525-topkill-diagram.html?ref=us


Methods That Have Been Tried to Stop the Leaking Oil




Efforts to Suppress the Flow of Oil

Since a fire engulfed the Deepwater horizon rig in the Gulf of Mexico on April 20, engineers have attempted a number of techniques to slow or stop the torrent of oil leaking from the wellhead 5,000 feet below the surface.

JULY 30TAKING IT FROM THE TOP, AGAIN

BP is expected to begin the process of sealing the Macondo well with the “static kill” as early as Monday. The method is similar to the top kill that failed in early June and would use existing equipment and plumbing. But this time, engineers can pump mud slower and at lower pressure because a new cap atop the well had stemmed the flow of oil. After the static kill, BP will proceed with killing the well from the bottom with the relief well.
Source: BP

JULY 14TESTING TO SEE IF THE WELL IS INTACT

With the new sealing cap in place, engineers will test the well’s pressure to determine its integrity.
Source: BP

JULY 10A BETTER CAP

In a procedure that would take several days, BP removed the well cap that was put in place on June 3 to replace it with a new one with the potential to completely stop the flow from the well. The new cap has some of the same types of components as the blowout preventer. Once installed, engineers will take pressure readings for up to two days. If the pressure is at an anticipated level, the cap could remain closed, ending the gusher.
Source: BP

MID-JULYADDING MORE CAPACITY

By mid-July, BP expects to have a total of four vessels on site to collect and process oil and gas. The Q4000 will be replaced by another vessel, Toisa Pisces, which will be connected to one of two floating risers that can be disconnected in the event of a hurricane.
Source: BP

JUNE 16CAPTURING MORE OIL

A second containment system has begun siphoning oil and gas from the leaking well. BP estimates the system will carry 5,000 to 10,000 barrels a day to the surface, supplementing the roughly 15,000 barrels collected daily by a containment cap on top of the blowout preventer.
Using equipment originally put in place to inject heavy drilling mud during the failed “top kill” procedure last month, the new system extracts oil and gas directly from the blowout preventer, passes it through a manifold on the seafloor and pipes it up to the Q4000 surface vessel.
The Q4000 has no storage capacity and will burn the oil and gas.
Source: BP

JUNE 4BEGINNING TO CAPTURE SOME OIL

A cap placed over the upper portion of the leaking well was funneling some oil and gas to a surface ship, though oil continued to billow from under the lip and through four open vents on top of the device. Methanol is being pumped into the cap to prevent the formation of icy hydrates that could block the mile-long pipe rising from the cap. Engineers hope to capture more oil by progressively closing the cap vents.
Source: BP

MAY 31ANOTHER ATTEMPT TO CAP THE WELL

After the failure of the top kill operation, BP began a new operation to cap the well. The damaged pipe will be cut from the blowout preventer, and a dome will be lowered over it to catch the spewing oil.
The new riser pipe will have a 6.625 inch internal pipe to capture leaking oil and gas. Methanol and warm seawater will be pumped down the riser to insulate the smaller pipe and prevent the formation of ice crystals which caused the earlier containment dome to fail.
Source: BP

MAY 26THE TOP KILL AND JUNK SHOT

BP tried two more operations, called the “junk shot” and the “top kill,” to stop the gushing oil. In the “top kill,” heavy drilling liquid is pumped into the well until the weight of the liquid overcomes the pressure of the rising oil. The “junk shot” involves injecting objects like golf balls to clog the blowout preventer, the stack of valves at the top of the well.
Source: BP technical briefings

MAY 16ATTACHING A TUBE

After several unsuccessful attempts, BP inserted a mile-long tube into the broken riser pipe to divert some of the oil to a drill ship on the surface some 5,000 feet above the wellhead. The tube siphoned off about 22,000 barrels of oil over nine days, but was shut off once the “top kill” operation began.

MAY 7LOWERING A CONTAINMENT DOME

BP constructed a four-story containment dome, intended to control the largest of the leaks. As the dome was lowered, crews discovered that the opening was becoming clogged by an icy mix of gas and water. The dome was set down on the seabed, 650 feet away from the leak, as officials decided how to proceed.
Source: BP

MAY 2DRILLING RELIEF WELLS

BP is drilling relief wells that may be used to plug its runaway well in the Gulf of Mexico. Once one of the new wells intersects the existing well, heavy drilling mud, followed by cement, will be used to stop the oil from leaking.
Source: BP

APRIL 30CHEMICAL DISPERSANTS

BP officials began injecting chemical dispersants underwater, near the source of the leaks. The dispersants, usually used on the water surface, is intended to break up the oil before it rises. The full environmental impact of the technique is unknown, but the E.P.A. has directed BP to change to a less toxic chemical than it had originally chosen.
Source: BP

APRIL 25REPAIRING THE BLOWOUT PREVENTER

The quickest way to stop the leak would have been to activate the well’s blowout preventer, a valve designed to seal off the well in an emergency. But several efforts to activate the blowout preventer failed.
Sources: United States Coast Guard; BP

How the Leak Started

Fire
Gerald Herbert/Associated Press
On April 20, the Deepwater Horizon, a drilling rig 50 miles off the coast of Louisiana in the Gulf of Mexico, exploded into flames. Two days later the rig sank, causing the 5,000 foot pipe that connected the wellhead to the drilling platform to bend. On April 24, robotic devices discovered two leaks in the bent pipe, nearly a mile below the ocean surface.
Overview


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