BP does not yet know if its "top kill" bid to seal the gushing oil well in the Gulf of Mexico will succeed but is finally reporting some progress. Ever since the explosion on the Deepwater Horizon drilling platform in late April, the Explainer has been answering readers' questions on what's being called the largest oil spill in U.S. history. (It's really more of an oil "spew.") Below you'll find a sampling of our previous columns.
Why is this particular well spewing forth so prolifically, while in other places we have to pump oil out of the ground ourselves?
Because it's under a lot of heavy rocks. Deep deposits, like those in the Gulf, are packed down very tightly by the rock column above them. If they are tapped carelessly, the oil will start to gush out all at once, Beverly Hillbillies -style. Deposits that are closer to the surface are under less pressure, and the oil may need to be pumped from the very first drop. Almost all wells need a little help eventually, as extraction diminishes their internal pressure. Engineers pump water or natural gas into the chamber to force out the remaining crude, which is later separated from the added fluids. (Click here for a more thorough explanation.)
Is there any use for the recovered oil?
Yes. Even the black gold that comes straight from deep-sea wells is mixed with water. So the purest oil from a spill—the stuff skimmed right off the top of the open seas—is just a more diluted version of the original. Once it has been separated from the water, refineries can process it for use in cars, furnaces, and the manufacture of milk jugs. And if the recovered oil is too salty, or too contaminated with small solids for all but the most technologically advanced refineries, it can still be used to power incinerators or brick kilns. (Click here for a more thorough explanation.)
Why does the oil slick appear to be orange instead of black?
Because the emulsion of oil in water consists of particles of many sizes, separated by water molecules. The way these particles scatter light (and produce color) depends on their size, and their size can change over time as they clump together or separate. (Click here for a more thorough explanation.)
BP may try clogging the faulty blowout preventer with shredded tires, knotted rope, and golf ballsin a process known as a "junk shot." Wait, golf balls?
You heard me, golf balls. When an oil company taps a well, they place a steel tower over the pipe that leads into the reservoir under the ground or sea floor. This tower, known as a blowout preventer, has a series of valves on its sides and top that can be adjusted to slow or stop the flow of oil. When the Deepwater Horizon rig sank on April 22, its blowout preventer sprung several leaks. In theory, a junk shot would stuff the tower with objects of different sizes, shapes, and textures, so that oil couldn't pass up through these leaks and into the ocean. The junk items would have to be strong enough to hold up against the pressure of the oil, which is gushing out with significant force. (Otherwise, they might be crushed to bits and flow through the leaky valves themselves.) Golf balls happen to be small enough to fill gaps between the rope and tires, and they're very, very sturdy—most are designed to withstand 2,000 pounds of force from a club. (Click here for a more thorough explanation.)
What would happen if a storm like Katrina tracked across the spill in the Gulf?
It could make things even worse. At least one forecast team puts the chance of a strong hurricane hammering some part of the Gulf Coast this year at 44 percent, and any such storm would threaten to disrupt ongoing containment or environmental protection measures. In an absolute worst-case scenario, powerful hurricane winds might drive the oil slick toward land and push some of it ashore with the ensuing storm surge.
Much depends on the angle at which the storm crosses the slick. In the Northern Hemisphere, hurricanes rotate counterclockwise, with the largest storm surge occurring where the winds blow in the direction the storm as a whole is traveling—that's in front of the eye and off to the right. So if a powerful storm approached the slick from the southwest, say, its most potent winds would push the oil forward instead of sweeping it off to the side and out of the storm's path. If the storm then plowed into the Gulf Coast, you'd expect an oily landfall. The strength, movement, and size of the storm would also make a difference. Fortunately, the height of the Atlantic hurricane season, featuring the strongest storms, doesn't arrive until August. We might reasonably hope to have cleaned up the oil by that point. (Click here for a more thorough explanation.)
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