Gulf oil spill poses unprecedented challenges for BP

LOS ANGELES - The oil spill in the Gulf of Mexico presents BP Exploration and Production with a problem of unprecedented severity - a limitless gush in very deep waters - forcing the London-based company to grasp for fixes never before tried.

The problem with the April 20 spill is it isn't really a spill: It's a gush, like an underwater oil volcano. A hot column of oil and gas is spurting into freezing black waters nearly a mile down, where the pressure nears a ton per inch - impossible for divers to endure. Experts call it a continuous, round-the-clock calamity, unlike a leaking tanker, which might empty in hours or days.

"Everything about it is unprecedented," said geochemist Christopher Reddy, an oil-spill expert and head of the Coastal Ocean Institute at the Woods Hole Oceanographic Institution in Massachusetts. "All our knowledge is based on a one-shot event ... With this, we don't know when it's going to stop."

Accidents have occurred before in which oil has gushed from damaged wells, he said. But he knew of none in water so deep. And "everything is bigger and more difficult the deeper you go," said Andy Bowen, a research specialist who works with undersea robotics at the Woods Hole center. "Fighting gravity is tough. It increases loads. You need bigger winches, bigger cables, bigger ships."

To BP falls the daunting task of trying to stop the gush before it becomes the most-damaging spill in American history. The company is working on three fronts at once.

Two options for blocking the flow are difficult, but at least rely on conventional technology. A third option - corralling the plume of oil and diverting it into a processing ship's hold - "has never been done in that depth and is stretching the boundaries," said BP spokesman Daren Beaudo.

But BP has no choice. Failure to stop the flow of oil from the sea bottom could undercut all other efforts under way to combat the spill, Reddy said.

It's not clear how the April 20 explosion happened. But experts say natural gas mixed with oil may have leaked up the pipe used to encase the drill and extract mud from the well. Natural gas expands as it is released from the seafloor and flows up. It can easily spark and explode.

In the disaster that followed, the rig sank, the riser bent and broke in at least two places. Key to the catastrophe was the failure of a blowout preventer sitting on the seafloor on top of the well. It failed to shut a valve to prevent oil escaping. BP officials say they believe there was an attempt to activate emergency systems, but they didn't work.

BP first deployed robotic submarines to shut the valve, but experts say conditions for this work are profoundly difficult. So BP is working on two other plans, one relying on conventional technology. Another hole would be drilled into the seafloor near the accident site. Heavy material and cement would then be squirted into the new hole in an attempt to plug up the reservoir. This process could drag on for 90 days, BP officials say.

So work is under way on an unproven concept: They are constructing three large subsea oil-collection systems. These are essentially 40-foot-tall steel boxes that BP plans to lower over the gushing sources in order to contain the oil and channel it up through pipes to a waiting processing ship.

The engineers are designing the new system without exact knowledge of the flow and force of the oil. Buoyancy and heat will force the oil upward, said David Valentine, a geochemist at the University of California, Santa Barbara. But there is danger of pressure building in the chamber as the oil gushes in. Or oil that is mixed with gas might cool too quickly as it rises, then stiffen, and clog the pipes, Valentine said.

BP said it would take two to four more weeks to build and install the collection systems.