BP hopes for success in 'killing' oil well as US puts pressure

BP plc's planned attempt this week to shut off its blown Gulf of Mexico well has a 60-70% chance of success, a BP executive said on Monday, as efforts to reduce the gushing oil leak faltered.

"We need it to work," BP chief operating officer Doug Suttles told CNN, referring to a so-called 'top kill' operation — the injection of heavy fluids and then cement into the seabed well to block oil flow.

The London-based energy giant, which has now lost about 25% of its market value — almost $50 billion — since the spill began five weeks ago, has scheduled the attempted fix for Wednesday.

BP is facing intense and growing pressure from the US government to solve what president Barack Obama has called an unprecedented environmental disaster for the United States.

With heavy oil already clogging fragile marshlands and wildlife refuges in Louisiana, soiling birds and turtles, BP engineers are racing to line up technical options to try to contain or seal the leak as soon as they can.

Seeking to rate the chance of success of the 'top kill' option on a scale of 1-10, Suttles said: "It's not a 10, it's not that certain, but it's above a 5 — a 6 or a 7."

Members of Obama's cabinet were to visit the fouled Gulf Coast on Monday. The administration warned BP on Sunday it would be removed from efforts to seal the well if it was not seen to be doing enough. But officials acknowledged that only the company and the oil industry have the know-how to stop what threatens to become the worst US oil spill.

BP shares fell around 3% in London on Monday, as investors reacted to the Obama administration's renewed pressure on the company to stop the leak.

"Really what everyone's waiting for is the top kill operation which should be coming up in the next couple of days.... That really is the key: whether they can actually kill off this well," Panmure Gordon analyst Peter Hitchens said.

A broker said investors were increasingly concerned that BP's future in the US, where 40% of its assets are located, was at risk.

BP executives have warned that there is "no certainty" that the containment efforts will work because they have not been attempted ever before at the depths — a mile (1.6km) down — where the Macondo well is located.

They involve undersea robots working in the dark and under intense depth pressure.

A previous control measure attempted by BP — a long tube deployed down to the larger of two leaks from the well — appeared to have had relatively little impact on the flow.

BP said the oil collected by the siphon tube was at times as low as 1,360 barrels of oil (57,120 gallons or 216,200 litres) a day in the six days before May 23.

On average, BP said, the oil captured during that period was 2,010 barrels a day. Last week the company said it had been siphoning as much as 5,000 barrels (210,000 gallons or 795,000 litres) a day.

The company had estimated that about 5,000 barrels have been leaking every day, though some scientists have given much higher numbers for the size of the leak — up to 70,000 and even 100,000 barrels per diem.

BP said the spill, which has seen oil flowing into the sea since after an April 20 rig explosion sank the Deepwater Horizon rig, killing 11 workers, had cost it $760 million so far, up from the $625 million estimate it reported on May 18.

Suttles said that if the 'top kill' operation did not work, then the company would attempt to put a 'top hat' containment device over the larger leak to try to capture most of the oil and pipe it up to a tanker on the surface.

Another option on the table was a 'junk shot' — the injection of golf balls, pieces of rubber tyre, and other debris into the well's failed blowout preventer to try to shut it.

Oil has been sloshing into Louisiana's fragile marshlands, and over 65 miles (110 km) of shoreline have been tarred.

Interior secretary Ken Salazar and homeland security secretary Janet Napolitano, accompanied by a US senate delegation, were to visit the state on Monday and fly over the affected areas.

Salazar said on Sunday that Washington was frustrated and angry that BP had missed "deadline after deadline" in its efforts to seal the well more than a month after an oil rig explosion triggered the disaster.

"If we find they are not doing what they are supposed to be doing, we'll push them out of the way appropriately," he said after visiting BP's US headquarters in Houston.

The spill has raised questions about Obama's earlier proposal to expand offshore drilling as part of a strategy to win Republican support for climate change legislation.

Analysts say ecological and economic damage from the spill could become a political liability before the congressional elections in November.

Many scientists have warned that the spreading oil could increasingly be caught in a powerful ocean current that could take it to the Florida Keys, Cuba, and the US East Coast.

Obama on Saturday blamed the mess on "a breakdown of responsibility" at BP and its partners in the well drilling.