BP may try "static kill": Allen

WASHINGTON/HOUSTON (Reuters) - BP Plc and U.S. government scientists are in talks about trying to plug its Gulf of Mexico well from the top with a so-called "static kill," the top U.S. spill official said on Tuesday.

Retired Coast Guard Admiral Thad Allen also told reporters at a briefing in Washington that he approved extending BP's key pressure test on the blown-out Macondo well another day.

He said that the new procedure could augment a relief well, which remains on target to kill the leak by mid-August.

"We'll probably have a good idea over the next 24 hours exactly what the detailed plan by BP would be to do that," he said.

Like BP's failed "top kill" in May, a static kill would involve pumping heavy drilling mud and cement into the well through a hose into a failed blowout preventer at the seabed.

Kent Wells, BP's senior vice president of exploration and production, explained at a separate briefing that the difference would be the cap atop that blowout preventer, which now shuts in all flows.

During the top kill, drilling mud pumped into the blowout preventer shot out of an uncovered pipe at the top along with leaking crude. The cap closes that escape route and keeps pressure manageable, Wells said.

The relief well is expected to intercept the blown-out well near its bottom, about 13,000 feet beneath the seabed, by the end of July, Wells said. Mud and cement would be pumped in to seal the well, and the static kill operation could so the same from the top.

"You can see how working in tandem, these would have the ability to have the well completely killed in less time," Wells said. "It's clearly worthy of us going through all the analyses we are."

The briefings Monday also revealed:

* BP is monitoring five leaks near the wellhead but "we've found nothing that would be consequential toward the integrity of the wellhead to date," Allen said.

* Officials are watching a weather system near Puerto Rico that could strengthen into a tropical depression and possibly interfere with operations at the spill site.

* The pressure test and monitoring has delayed BP's plan to assemble a four-vessel oil-capture system that can handle up to 80,000 barrels a day by the end of July, Allen said. "At some point we will have to make a decision" on whether to stop the test and work to get that system in place.

* U.S. scientists are discussing whether they can refine their estimate of the leak's flow rate of up to 60,000 barrels a day with pressure and temperature readings rather than reopen

the well and resume siphoning oil to surface vessels, Allen said.

(Editing by Eric Walsh)