So far, so good on 'top kill' plug

The "top kill" is under way, success uncertain. BP engineers are pumping mud at a furious rate into the damaged blowout preventer that sits on the uncapped well at the bottom of the Gulf of Mexico.

The early bulletins on the top kill were encouraging. "The operation is proceeding as we planned it," BP Chief Executive Tony Hayward said Wednesday evening, adding that it would be 24 hours before BP knows if the well is dead.

The billowing plumes of effluent from cracks in the top of the riser pipe no longer look like oil and gas, but have a distinctly muddy appearance.

"What you've been observing out of the top of that riser is most likely mud. We can't fully confirm that because we can't sample it," BP Chief Operating Officer Doug Suttles said at a news conference Wednesday night.

Speaking cautiously, he noted that if all goes as hoped, the well could be cemented shut by Thursday night.

BP officials, having studied pressure readings, finally pulled the trigger on the top kill Wednesday afternoon.

The world could follow the top kill via live video feeds from robots on the seafloor.

It was strikingly similar to watching an Apollo moon landing: grainy images of unfamiliar technology in an alien landscape.

The procedure pumps heavy drilling mud from a ship on the surface down to the sea floor and into the five-story-tall blowout preventer atop the well.

If all goes as planned, the mud will slide about 2 1/2 miles down to the bottom of the well bore, rendering the well "static."

Engineers would follow up with cement plugs to seal the well permanently.

Much could go wrong.

The pressure of the injected mud could damage the blowout preventer and exacerbate the leaks.

The mud would go wherever it can, and not necessarily where the engineers would prefer.

"There's a hole, but it's kind of like pushing toothpaste through an obstacle course," said Bruce Bullock, director of the Maguire Energy Institute at Southern Methodist University.

Millions of gallons of oil — and possibly tens of millions — have leaked into the Gulf since the April 20 explosion and fire that killed 11 crew members on the drilling rig Deepwater Horizon, which sank two days later.

Oil has touched 84 miles of Louisiana's ragged shoreline and envelops the crow's foot of the Mississippi River delta.

The oil trajectory forecast by the National Oceanographic and Atmospheric Administration indicates that some of the oil has been captured by the Gulf's Loop Current and by noon Friday could spread approximately as far south as, but considerably to the west of, Key West, Fla.