Efforts To Stem The Deepwater Horizon Oil Spill

Efforts to stem the ''Deepwater Horizon'' oil spill were ongoing from the time that the ''Deepwater Horizon'' exploded on April 20, 2010 until the well was sealed by a cap on July 15, 2010. Various species of dolphins and other mammals (61 casualties), birds (2,095 casualties), and the endangered sea turtles (467 casualties) have been killed either directly or indirectly by the oil spill. The ''Deepwater Horizon'' spill has surpassed in volume the 1989 ''Exxon Valdez'' oil spill as the largest ever to originate in U.S.-controlled waters; it is comparable to the 1979 Ixtoc I oil spill in total volume released (Ixtoc discharged to ; as of mid-July 2010, Deepwater Horizon had spilled to ).

Much of the oil is so far down in the Gulf that only nature, including microbes, will be able to remove it using a process called bioremediation.Berkeley scientist advises on clean-up in gulf oil spill - June 4, 2010
U.S. Fish and Wildlife Service. 5 July 2010. Terry Hazen of the Department of Energy's Lawrence Berkeley National Laboratory said the process could take months or years. But after six weeks of research, he said that microbes could work quickly in water as opposed to colder-temperature waters. The '' A Whale'', which is an oil tanker converted into a giant oil skimmer owned by the Taiwan Marine Transport Co (TMT), could do little because of BP's use of chemical dispersants, the company said. Robert Bea of The University of California, who worked on the Ixtoc spill and the 1969 Santa Barbara oil spill, said the old methods would be the best ones. Dispersants, he said, did not work except in keeping beaches clean, and they hurt the environment.

Closure attempts

Short term efforts

The first attempts to stop the oil spill were to use remotely operated underwater vehicles to close the blowout preventer valves on the well head; however, all these attempts failed. The second technique, placing a containment dome (which had worked on leaks in shallower water) over the largest leak and piping the oil to a storage vessel on the surface, failed when gas leaking from the pipe combined with cold water formed methane hydrate crystals that blocked the opening at the top of the dome.

On May 14, engineers began the process of positioning a wide riser insertion tube into the wide burst pipe. There was a stopper-like washer around the tube that plugs the end of the riser and diverts the flow into the insertion tube. The collected gas was flared and oil stored on the board of drillship ''Discoverer Enterprise''. of oil was collected before removal of the tube.

On May 26, BP tried to close the well using a technique called "top kill", which also failed. This process involved pumping heavy drilling fluids through two lines into the blowout preventer to restrict the flow of oil before sealing it permanently with cement.

On May 29, BP moved to the Lower Marine Riser Package (LMRP) Cap Containment System by removing the damaged riser from the top of the blowout preventer and covering the pipe by the cap which connects it to a riser. The cap was attached on June 3, and the system began to capture the leaking oil. On June 6, the CEO of BP Tony Hayward, stated that the amount captured was "probably the vast majority of the oil." However, Ira Leifer, a member of the Flow Rate Technical Group (FRTG), claimed that more oil was escaping than before the riser was cut and the cap containment system was placed.

On June 16, a second containment system connected directly to the blowout preventer became operational carrying oil and gas through a subsea manifold to the '' Q4000'' service vessel with a processing capacity for about of oil per day. Oil and gas are both burned on ''Q4000'' in a clean-burning system.

As ''Discoverer Enterprises processing capacity was insufficient, drillship ''Discoverer Clear Leader'' and the floating production, storage and offloading (FPSO) vessel '' Helix Producer 1'' were added, offloading oil with tankers ''Evi Knutsen'', and ''Juanita''. Each tanker has a total capacity of . In addition, '' FPSO Seillean'', and well testing vessel ''Toisa Pisces'' would process oil. They are offloaded by shuttle tanker ''Loch Rannoch''.

On July 5, BP announced that its one-day oil recovery effort accounted for of oil, and the flaring off of of natural gas. The total oil collection to date for the spill was estimated at . The government's estimates suggested the cap and other equipment were capturing less than half of the oil leaking from the sea floor as of late June.

On July 10, robots removed the containment cap to replace it with a better-fitting cap ("Top Hat Number 10"); this meant all of the leaking oil would escape until the new cap was in place. A broken pipe was taken out on July 11 and replaced with a flange spool resembling a pipe, on top of which the new cap was located. The well integrity test was scheduled to take place after the installation of a three-ram capping stack over the lower marine riser package of the Deepwater Horizon semi-submersible rig on . On July 14, BP announced that the test would be delayed under Allen's orders; oil continued to flow into the Gulf.

Temporary closure

On July 15, 2010, BP announced that it had successfully plugged the oil leak using a tightly fitted cap. The cap, weighing 75 tons and standing high, was bolted to the failed blowout preventer. It consisted of a Flange Transition Spool and a 3 Ram Stack and was a temporary solution.

President Barack Obama cautiously welcomed the news that the leak had been stopped, while stressing "it is important we don't get ahead of ourselves". If the cap held for the planned 48 hours, the plan was to temporarily reopen the valves in order to allow for seismic tests to ensure that oil was not escaping into the bedrock. At the time of the stoppage, oil had been leaking continuously into the Gulf of Mexico for 85 days, 16 hours and 25 minutes since the ''Deepwater Horizon'' drilling rig exploded on April 20, 2010.

Until July 19, 2010, there was no evidence that the well had ruptured, meaning that the cap appeared to be working. According to Thad Allen, the retired US Coast Guard admiral in charge of the operation to stop the leak, the cap would be used to channel the flowing oil to surface ships for collection after the 48-hour test period and would be used to shut the well down during bad weather rather than permanently cap the well, which was expected to happen in mid-August 2010, when relief wells had been completed. On July 19, 2010, seepage was detected from the seafloor within two kilometres of the well. Allen believed that it probably has nothing to do with the well, as oil and gas are known to ooze naturally from fissures in the bottom of the Gulf of Mexico.

On July 22, forecasts of the track of tropical storm Bonnie made it imperative that the support ships and rigs leave the site. Allen, in consultation with Energy Secretary Steven Chu

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