Stopping the Gulf of Mexico oil leak
BP has tried a number of methods to shut down the leak from the damaged oil well - often innovating as subsequent attempts have failed.
Although some of the methods have been tried and tested at incidents elsewhere in the world, they have not been carried out at such great depth as the Deepwater Horizon leak - 5,000 feet (1.5km) below the surface.
After the failure of the top kill procedure, BP attempts to cut the top off the upper section of the blowout preventer (BOP) and place a cap on it, sealing the leak and taking oil to a ship on the surface.
After a brief setback with some of the cutting equipment, the cap is installed and BP announces on 4 June that it is collecting oil at a rate of 1,000 barrels a day.
Turning their focus to the blowout preventer or BOP that sits over the well head, BP try to stem the flow of oil and gas and ultimately kill the well by injecting heavy drilling fluids.
The procedure includes injecting a "junkshot" of golf balls, rope and rubber into the BOP in a bid to block the flow.
Despite pumping more than 30,000 barrels of heavy mud itno the BOP and a range of junkshot, the operation fails to overcome the flow from the well.
BP had some success with a "riser insertion tube" - a pipe with rubber diaphragm inserted into the leaking part of the riser pipe that is the source of the main oil flow from the well.
The insertion tuibe is connected to its own riser pipe that takes the oil and gas to the Transocean Discoverer Enterprise drillship, 5,000ft (1,524m) above on the surface.
Methanol is injected into the tube to stop the formation of hydrates - crystals that could block the flow of oil and gas.
The tube tool has been able to collect about 3,000 barrels a day of oil and some 14 million standard cubic feet a day of gas.
The oil is being stored and gas is being flared on the drillship Discoverer Enterprise - which has the capacity to store 139,000 barrels of oil.
Plans to place a large containment dome over the main leak and siphon oil to a ship on the surface is aborted as hydrates or ice crystals build up, blocking the pipes.
A smaller "top hat" dome is lowered to perform a similar task, but engineers decide to use insertion tube instead.
BP is drilling two relief wells in an additional effort to relieve the flow of oil. Work on the first relief well started on 2 May, with the second starting on 16 May. Both wells are expected to take around three months to complete from the start of drilling.