BP said that the tests on the newly capped Gulf of Mexico oil well show pressure has been building up slightly as hoped, with no signs of leakage. (photo, from bbc.co.uk)
Kent Wells, BP vice-president, said rising pressure “is giving us more and more confidence”.
Yet tests could be extended beyond Saturday.
Thanks to the new cap, it is the first time that the flow of oil has been stopped since a 20 April explosion killed 11 people.
The spill, which has been described as the worst environmental disaster in the US, has affected hundreds of miles of Gulf coastline since April.
There is also a serious economic damage to the region because tourists have avoided Gulf Coast beaches, and fishing grounds have remained closed.
BP has put the costs of dealing with the disaster at over $3.5bn.
Though is has already paid out more than $200m to 32,000 claimants, the company is evaluating a further 17,000 for payment and is seeking more information on 61,000 other claims.
The flow of oil was shut off on Thursday at 14:25 local time (19:25 GMT), as part of a test of well’s integrity.
If the pressure within the new cap on the well stays high, it could mean that there are no other leaks or ruptures within the well bore, but if it drops, that could suggest problems.
When the initial testing was coming to an end on Saturday, Wells said : “We’re feeling more confident that we have integrity.”
“At this point there’s no evidence that we don’t have integrity,” he said at a regular news briefing.
“That’s very good and the fact that the pressure continues to rise is giving us more and more confidence as we are getting through the test.”
However, Wells indicated that the test could be extended. “The longer the test goes, the more confidence we have in it,” he said.
What will happen next remains unclear. The company has suggested that with oil collection vessels left on standby, it might be possible to keep the well shut.
But the US official overseeing the spill response, Adm Thad Allen, has suggested the most likely outcome is the resumption of collection of the oil with four vessels and the capacity to collect 80,000 barrels – all or virtually all of the oil – each day.
BP is also resuming work on two relief wells in order to intercept the damaged well and use mud and cement to permanently seal it.
The first of these wells is scheduled to be completed in August.