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