A pivotal moment in the Gulf oil crisis hit an unexpected snag when officials announced they needed more time before they could begin choking off the geyser of crude at the bottom of the sea.
BP and federal officials did not say what prompted the decision or when the testing would begin on a new, tighter-fitting cap it just installed on the blown-out well.
The oil giant had been scheduled to start slowly shutting off valves on the 75t cap, aiming to stop the flow of oil for the first time in three months.
It seemed BP was on track to start the test yesterday afternoon. The cap, lowered over the blown-out well on Monday night, is designed to be a temporary fix until the well is plugged underground.
A series of methodical, preliminary steps were completed before progress stalled.
Engineers spent hours on a seismic survey, creating a map of the rock under the sea floor to spot potential dangers, like gas pockets. It also provides a baseline to compare with later surveys during and after the test to see if the pressure on the well is causing underground problems.
An unstable area around the wellbore could create bigger problems if the leak continued elsewhere in the well after the cap valves were shut, experts said.
“It’s an incredibly big concern,” said University of Houston director of professional geoscience programmes Don Van Nieuwenhuise.
“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.”
It was unclear whether there was something in the results of the mapping that prompted officials to delay the tests. Earlier, BP vice president Kent Wells said he had not heard what the results were, but he felt “comfortable that they were good”.
National incident commander Thad Allen met with the federal energy secretary and the head of the US Geological Survey as well as BP officials and other scientists after the mapping was done.