BP begins testing on well cap

WASHINGTON — Following a daylong delay marked by intense double-checking and a briefing for President Obama, the government's spill team decided to let BP begin testing the seal on a massive 75-ton pipe fitting that could finally stop the three-month gush of oil and gas from the company's failed well in the Gulf of Mexico.

The company was scheduled to begin the well integrity testing Tuesday afternoon, but was ordered by the government to stop until experts could go through all the possible side effects. In particular, they were uncertain about the condition of the well — and whether additional pressure on the new seal would force oil and gas to leak out of weak spots deep below the floor of the ocean.

The 24-hour pause was a result of "an overabundance of caution," said the national incident commander, Adm. Thad Allen.

Mostly, they feared making an already dire situation irrevocably worse, Allen said.

"This has been a substantial impact on our environment, there's been a substantial impact on the Gulf Coast, the people and the culture," Allen said. "What we didn't want to do is compound that problem by making an irreversible mistake."

A delay allowed them to incorporate the results of seismic testing, which found none of the weakness they feared, Allen said.

The integrity testing will begin by slowly closing off the well, gradually building up pressure — a process Allen described to reporters at a briefing in New Orleans using a hand-drawn diagram on a dry-erase board. The process is expected to take about 48 hours, and will be halted every six hours to examine acoustic data and pressure levels to decide whether to proceed.

Allen said drilling experts will be trying to determine whether pressure can be maintained without an effect on the wellbore and its casing. If pressure drops, that signals there's a potential weakness in the well and that oil and gas could be escaping elsewhere. They want the pressure to remain constant.

If it remains stable after 48 hours, that's when they'll decide whether to move forward with activating the containment cap, Allen said.

What they learn from the integrity testing about the condition of the well will help inform how they proceed with the relief wells, which are nearing completion.

The drilling of the relief wells — considered the most likely method to permanently seal the blown-out well — also was halted during the integrity testing process.

The government has estimated that the well is spewing some 60,000 barrels a day into the Gulf.