After months of fruitless effort, BP has finally put a stopper on the Deepwater Horizon well, halting the flow of oil into the Gulf of Mexico.
The company says the cap is a temporary fix and offers no guarantees of success. As engineers continue watching the well for any changes deep underground, here's a look at possible next steps in the Gulf.
The Cap
BP engineers are monitoring the cap around the clock, looking for telltale pressure changes that might indicate problems in the concrete casing that lines the well. High pressure readings would indicate that the well walls are holding. Low pressure, below 6,000 pounds per square inch or so, could mean more leaks farther down in the well.
-- If the test is declared a success, one possible next step would be to permanently kill the oil flow with a mud-and-cement plug injected from a relief well still being drilled. But engineers could opt to reopen some or all of the valves and bring the oil to the surface as an extra precaution against damaging the well.
-- If pressure readings signal further instability, engineers would be forced to reopen valves on the cap stack and allow at least some of the oil to begin flowing again. If that happens, they hope the new tightly fitting cap will divert more of the crude so that it can be collected by ships.
In the weeks since the April 20 disaster, an estimated 92 million to 182 million gallons of oil have flowed into the Gulf. Before the well was sealed Thursday, the government estimated a daily flow of 1.5 million to 2.5 million gallons. At best, BP ships on the surface have been able to collect about 15,000 barrels a day -- 25 percent to 40 percent of the total.
The Relief Well
Regardless of the final outcome of the cap testing, BP will go ahead with what it has said all along is the only proven, permanent way to shut off the undersea gusher -- relief wells. For weeks, the company has been drilling two such wells.
A relief well intercepts the main well and is meant as a conduit through which to force a mud-and-cement plug that will permanently close off the flow of oil.
The first relief well was begun on May 2, and work on a second one -- drilled on the opposite side of the main well as a precaution in case the first one failed to reach its target -- was started two weeks later. BP expects the first to reach its target by the end of the month. The company thinks it could proceed with injecting the plug material sometime in August.
That procedure would effectively end the spill, leaving the enormous task of cleaning up.
The Cleanup
No one knows yet how exactly to scour hundreds of miles of fouled Gulf coast shoreline or how much it will cost.
Last month, Louisiana Treasurer John Kennedy estimated the total Gulf cleanup cost at $40 billion to $100 billion. The state has been hardest-hit by the spill, and Gov. Bobby Jindal unveiled a plan Wednesday to restore the coast, asking the federal government for $9 billion.
A number of skimmer ships, including a giant Taiwanese vessel capable of collecting 21 million gallons a day of oily water, are already in operation or are en route to the Gulf.
The economic fallout from the spill is likely to be felt for a very long time. About one-third of the region's fisheries have been shut down, and it's uncertain when they could be reopened.
Last week, BP said it had already spent $3.1 billion on the cleanup, which is likely to take years or possibly decades. On Friday, the company said 114,000 claims for damages from fishermen and other businesses have been filed. A total of $201 million worth of claims have been settled so far.
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