If the initial disaster weren't so tragic, and the potential environmental impact so cruel, oil giant BP's response to the Deepwater Horizon would almost be humorous. At press time, the offshore well in the Gulf of Mexico was still leaking some 5000 barrels of oil per day, with approximately 80 percent of that gush diverted, according to BP, into a storage vessel at the surface. How the oil company has achieved partial control over the crisis, and how it hopes to staunch the wound entirely within the coming weeks, is a strange tale, full of seemingly half-baked solutions and an excess of crossed fingers. That's not to say that BP is necessarily handling its mission poorly—the truth is that every offshore leak has its own unique conditions and potential complications. "There is no standard operating procedure for these kinds of incidents," says Richard Sears, former head of offshore oil exploration for Shell, and currently a visiting scientist at MIT. "That would be because they don't happen very often. The initial response, the skimming vessels and miles of floating boom you deploy to contain the spill, that's all standard. You know you'll have a positive impact with those. The rest is all custom solutions."
Whether BP is ultimately taken to task for the apparent failure of the blowout preventer—a device that literally shears through the well in an emergency, blocking the up-surge of gas bubbles that seems to have ignited at the rig—or for the speed of its response, the company's attempts at improvising its way toward a resolution is business as usual in offshore oil production. Here's a rundown of the options that have either been tried or are still on the table, ranked from the safest, most practical bets, to the riskiest, longest shots ever concocted by some of the world's smartest engineers.
No two wells rupture in exactly the same way. The Deepwater's primary leak is occurring in the riser, a 6-inch-wide pipe that connects the rig to the subterranean well structure. The base of the riser is a complex system of valves and additional pipes, including the blowout preventer (BOP). In the aftermath of the explosion that tore through the rig, killing 11 crew members, the base became the spewing mouth of the 6-mile-deep oil zone, ejecting oil and natural gas at a steady rate of 50,000 barrels per day. BP deployed remote-operated vehicles (ROVs), the same underwater robots that the oil industry relies on to install and maintain offshore wells at depths that would be lethal to human divers, to make manual adjustments to whatever's left of the riser's BOP. Blowout preventers typically have choke lines, which can be used to restrict the well's flow, as well as kill lines, which cut the flow entirely. Initial attempts to slow or block the leak with these lines have failed.
That doesn't mean the riser is useless, though. The most effective tactic so far has been the most straightforward one, using ROVs to insert a thinner, 4-inch-wide pipe into the riser. BP is referring to this as a "riser insertion tool." The media call it a "straw." Let's call it a temporary fix, since it allows the majority of the oil and natural gas leaking out of the well to be sucked up to the surface.
Though not the most optimal way to squeeze hydrocarbons from the earth—the siphoned oil is being recovered, but the natural gas is flared as it is collected—the straw tactic is looking smarter by the day. Engineers have gradually increased the amount of fluid that can be drawn though the riser insertion tool, and according to Sears, a 4-inch-wide pipe should ultimately be able to handle the full 5000 barrels per day.
If the straw comes loose, the leak is back to full strength. But the real gamble was in the original insertion—the damaged riser's structural integrity is unknown, and any prodding could have worsened the spill, or prevented any hope of other riser- or BOP-related fixes.
The Top Kill
With the majority of the leak now funneled through the riser insertion tool, and no signs of additional degradation of the riser, BP appears ready to attempt a complete and somewhat orderly shutdown of the well. The procedure is called a "top kill" and would involve pumping heavy mud and other drilling fluids into the riser's still-functioning valve structure. Once the flow becomes a trickle, crews would chase the mud with concrete, eventually plugging the entire riser and much of the well's structure near the seabed. BP is reportedly planning a top kill as soon as May 23rd. That would be a happy ending. Or as happy as this story can possibly end.
Top kills are probably the most routine of the tactics that BP has tried or has yet to rule out.
Unfortunately, no one has attempted a top kill at depths of 5000 feet. And while the riser does not seem to be getting worse, there's always the chance that it could break up or otherwise fail before a sufficient amount of mud and/or cement is pumped into it.
The Dome, the Tophat and the Sombrero
Before the straw, there was the now-infamous dome, a 125-ton concrete-and-steel cap that was positioned over the open riser by robots. The hope was that the leaking oil and natural gas could be contained within the four-story dome, and drawn up through a tube to the surface. It took days for the container to be lowered to the ocean floor. It took far less time for the plan to fail, as the dome's umbilical hose quickly became clogged with methane hydrate, a slush that can form in oil wells when temperatures dip low enough. The temperature at the Deepwater's riser was on the cusp of freezing, at roughly 30 F, but the water and oil mixture remained fluid because of the extreme pressures (around 2500 psi). As soon as that mixture was isolated from sub-5000-foot pressures, the methane hydrates formed almost immediately. It's a problem that's common in offshore oil production, says Sears, where crews use warm water and antifreeze-like compounds to keep flow lines clear. The most likely explanation for why BP went ahead with the dome anyway: Because it was there. "They probably said, There's a real risk of a hydrate problem, but we've got this thing. It's worth a try," Sears says.
BP currently has a smaller container on the seafloor near the spill; it was delivered after the original dome was scrapped and could be deployed in the coming days or weeks. This "tophat" is fully equipped to fight methane hydrate formation. There are no announced plans to use it, but the tophat could be maneuvered into position relatively quickly.
The dome is a proven solution—sort of. A similar steel container, called the sombrero because of its shape, was used more than 30 years ago to seal off an offshore oil leak in Mexico's Bay of Campeche.
It's important to note that it took two tries to get the sombrero to work back in 1979. And after the Deepwater dome's initial failure, throwing the more sophisticated tophat into the ring would mean disengaging the straw, and possibly making a bad situation even worse.
The Junk Shot
If all else fails—the top kill, the tophat, or any number of jury-rigged solutions that engineers and researchers could propose if this well continues to gush—then BP may try a junk shot. The name says it all: a mass of golf balls, rope and other seemingly random bits would be launched into the open riser. It's a tactic of last resort, and precisely as desperate as it sounds. "The junk shot is not about solving the problem in some controlled fashion, but putting a bunch of crap down there to plug the well long enough so you can go in and reattach the rig," Sears says. The goal is for the various pieces of junk to snag on the riser's pipes and valves, eventually wadding and blocking the entire mouth of the well.
The junk shot wasn't invented to handle this particular leak, but it's generally used to plug leaks aboveground. On paper, the cocktail of shredded tires, golf balls and other materials could either do the job that heavy mud and concrete might not, or pave the way for a subsequent top kill.
As with nearly every attempted fix, the danger here is aggravating the wound, possibly tearing the riser to shreds and increasing the flow of leaked oil tenfold or more. BP is already facing claims—warranted or not—of incompetence and negligence. And while it's hard to draw accurate comparisons, attempting to fix this leak is along the lines of performing heart surgery in the dark without a single X-ray, and the entire world watching the prodecure live. If the company turns an environmental disaster into a catastrophe by going a bit too heavy on the golf balls, BP and the rest of the oil industry could lose what little public support they have left.