I don't understand enough of this to interpret what's going on, but it doesn't sound good:

NEW ORLEANS -- Worried about triggering another blowout -- possibly deep down a well of uncertain condition -- BP and federal officials have put the brakes on the latest effort to choke off the undersea geyser of crude.

Instead, they ordered a new round of analysis scheduled to start Wednesday before moving forward with pressure tests intended to determine whether a new 150,000-pound cap and a well three miles below the sea floor are strong enough to withstand the powerful flow of oil and gas.

The decision was made Tuesday in Houston, where U.S. Energy Secretary Steven Chu and a team of federal and industry scientists and geologists are overseeing BP's plans to run a "well integrity test."

"As a result of these discussions, we decided that the process may benefit from additional analysis," U.S. Coast Guard Adm. Thad Allen, who is in charge of the federal effort, said in a statement issued Tuesday afternoon.
After successfully placing a new and beefier cap on the blown-out well, the oil giant had been scheduled to start slowly shutting off valves, aiming to stop the flow of oil for the first time in three months.

If the cap works, it would enable BP to stop most, and possibly all of the oil, now gushing into the sea. The company could either use the cap as a cork to "shut in" the well. Or, if capping would create too much pressure, use the more sophisticated new cap to channel as much as 60,000 barrels a day through pipes and lines to as many as four collection ships.

Neither BP nor the federal government offered an immediate explanation of the additional analysis, but in briefings early in the day, it was clear there are still significant questions about conditions of gear on and underneath the sea floor -- particularly the casing that lines the well.

Those concerns also had prompted Chu to halt BP's earlier "top kill" effort to pump heavy drilling mud down into the well. Kent Wells, a BP senior vice president, told reporters in a conference call from Houston Tuesday afternoon that the integrity test would indicate whether there was damage inside the well. If the pressure doesn't build up as valves are closed on the new cap, he said, it would point to a breech that could worsen if the well is simply capped.

In the worst-case scenario, it could trigger a blowout deep beneath the sea floor that would be difficult, and perhaps impossible, to control -- at least until BP finishes drilling relief wells. That effort is still expected to take until mid-August.