2010-07-15 06:33

In this image taken from video provided by BP PLC at 18:17 CDT, a new containment cap, top, is lowered over the broken wellhead at the site of the Deepwater Horizon oil spill in the Gulf of Mexico, Monday, July 12, 2010. [Agencies]

HOUSTON - BP Plc will move ahead with a much-anticipated pressure test on a cap at its gushing Gulf of Mexico wellhead on Wednesday evening, the top US official overseeing the spill response said.

Retired Coast Guard Admiral Thad Allen said a closer analysis of the test and its possible ramifications reinforced confidence it would not exacerbate the leak.

"We'll be releasing an order to BP to proceed with the well integrity test, but we gave them some additional direction. We did this to be sure we were taking due care ... to make sure we didn't do any irreversible harm to the wellbore," Allen said.

Earlier in the day Doug Suttles, BP's chief operating officer for exploration and production, told CNN BP and US government scientists had decided on Tuesday afternoon to delay the test for 24 hours out of concern it could damage the stricken well and allow oil and gas to escape out the sides while the top was shut off.

But Allen said BP had provided information on piping in the stricken wellbore that assured officials of its structural strength. Taking the 24-hour break for more discussion "makes sure we're getting this absolutely right," he said.

The six- to 48-hour test will entail shutting in all leaking crude to gauge pressures.

BP and Allen have repeatedly said they don't know if the April 20 blowout damaged the pipe, or casing, and cement in the Macondo well. Such breaches could allow hydrocarbons to escape and possibly burst through the seabed if the cap were shut.

Allen said on Wednesday seismic data gathered on Tuesday "removed the possibility of a negative event," or hydrocarbons leaking out from the well beneath the seabed.

Allen also said that BP is moving forward with increasing oil-capture capacity with four vessels on the water's surface later this month.

If the cap can shut in all the crude, the vessels will be on site to step in if a problem erupts, he said.

Nansen Saleri, former head of reservoir management for Saudi Aramco, the world's largest oil company, told Reuters earlier on Wednesday that BP should scrap the test and keep using surface vessels to collect leaking crude until a relief well intercepts and plugs the leak by mid-August.

Two vessels captured or burned off 17,060 barrels of oil on Tuesday, and more are on tap to be hooked up and collect up to 80,000 barrels a day by the end of July, according to BP.

"They already have a relatively robust remedial program in place. It's the safe option," said Saleri, now president and chief executive of Quantum Reservoir Impact in Houston.

Kent Wells, BP's senior vice president of exploration and production, told reporters earlier that drilling had stopped on the relief well pending completion of the well test.