BP has suffered yet another setback in its efforts to stem the flow of oil into the Gulf of Mexico, announcing it has been forced to postpone planned tests on turning off valves on a new tighter-fitting cap over the leak.
The gradual shut-off was seen as the first real chance to stop the leak since the start of the environmental disaster almost three months ago.
A White House spokesman had said the operation "represents the best news that we've had in the preceding 85 days".
But Thad Allen, who is overseeing the US response to the crisis, has said that "additional analysis" is needed before the tests can start.
BP has confirmed that analysis is getting under way. "Consequently the well integrity test did not start," it said in a statement.
"It's an incredibly big concern," said Don Van Nieuwenhuise, the director of professional geoscience programmes at the University of Houston. "They need to get a scan of where things are – that way when they do pressure testing they know to look out for ruptures or changes."
The newly installed "capping stack" has a better seal than the last cap placed on the well and aims to stop oil from spewing out of the failed blowout preventer.
Experts said stopping the oil too quickly could blow the cap off or further damage the well.
BP has said the only way to permanently stop the leak is the drilling of two relief wells to intercept the ruptured one. The first is expected to intercept the oil leak by the end of July and plug it with drilling mud and cement by mid-August.
Before the decision to postpone the tests preliminary steps were completed, including mapping the sea bed.
Engineers spent hours on a seismic survey, creating a map of the rock under the sea bed to spot potential dangers like gas pockets. It can be compared with later surveys during and after the test to see if the pressure on the well is causing underground problems.
Experts have said an unstable area around the well could create bigger
© Guardian News and Media Limited 2010
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