Gulf oil spill: plugging the leak

BP engineers may try to bung up the Deepwater Horizon leak by pumping debris such as bits of tyres and golf balls into the well. It's a long shot known as a 'junk shot', but it might just work

Since the Deepwater Horizon explosion two weeks ago, it has been hard not to view as primitive the efforts to contain the oil and prevent more of it leaking.
Whether it is the containment booms drafted in to prevent the oil washing ashore or early efforts to set the oil on fire, or even the attempts to funnel the leaking oil via giant sunken towers, the somewhat low-tech containment efforts starkly contrast with the often hi-tech methods usually witnessed in deep-sea drilling.
The latest BP plan being weighed up is similarly low-tech. Engineers may try to plug the well by pumping debris into it at high pressure, a method known as a "junk shot".
"They are actually going to take a bunch of debris - some shredded up tyres, golf balls and things like that - and under very high pressure shoot it into the preventer itself and see if they can clog it up to stop the leak," the US Coast Board Admiral Thad Allen told CBS News yesterday.
Tyres, golf balls, and "things like that" do not immediately inspire confidence, However Dr Simon Boxall, oceanographer at the National Oceanography centre in Southampton, Hampshire, said the unique conditions of the Deepwater Horizon spill – there has never been an oil leak at this depth before – mean all traditional methods "go out of the window".
There have been blow outs in shallow water, but with those you're looking at 100-metre-deep tops, where you can get divers down and you can get equipment down," he said.
"It's nothing compared to doing it 1,500m [5,000ft] down – this goes beyond all our technological knowhow and experience.".
Boxall said a junk shot has been tried before, although he was only aware of one incident, which took place at a much shallower depth.
"We're working in completely new territory, but the idea is not quite as daft as it sounds," he said.
"Bear in mind the pressures at these depths are phenomenal, so what seems like an odd thing to bung a hole with at the surface can actually work quite well. Golf balls seem really quite hard but actually they're quite soft.
"Certainly if you add a tonne of pressure per square inch to a golf ball then it starts to give. So I guess what they're looking to do is use these things that are slightly plastic in their feel to bung into a hole which will help bung it up."
The main problem for engineers is how to get the debris into the well almost a mile beneath the surface. The plan is to block the well beneath the semi-operational cut-off valves – at the moment, the well is partly shut off, restricting the oil flow – without making the spill worse.
"They're planning to sort of try and insert them somehow magically before the cut off valve, but that doesn't quite make sense," Boxall said.
"All these things you can imagine are perfectly feasible on land if you had whatever technology was available to bung them in the hole.
"But when you're looking at some mechanism to fire them into a hole when you're a mile down in seawater, I can't imagine what they would use, unless they're using compressed air – but that is difficult at those depths anyway because the pressures are so great."
He added: "There are one or two engineers out there who seem to be thinking: 'This is ok as long as we don't cause more damage than we solve.'"
BP's ultimate solution to the leak is to drill a relief well, but that could take up to three months before that is completed. In the meantime, they will continue to try and position a cofferdam over one of the leaks today.