BP has blasted mud down the shaft of its broken well in an operation it says could once and for all put an end to the biggest off-shore oil spill in US history.
The technique they have used to stem the flow is called a “static kill” and the graphic below which ran in the New Zealand Herald today explains how it works. See bottom for how UK-based scientists have responded to news of the operation’s success.
Comment gathered by the Science Media Centre based in London:
Prof Malcolm Fox, Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds, said:
’The issue is that the oil which has been evaporated, burned or dispersed is the lighter/middle fraction of the spilt crude oil. The material remaining will be the heavier fractions which may agglomerate, e.g. as ‘tar balls’, which will take longer to degrade.
’A saving grace, if there is one, is that the Mexican Gulf crude appears to be lighter than, e.g., Middle Eastern, crude oils and there will be less of the heavy fraction in it and therefore less to deal with. Once widely dispersed, the bacteria in the warm Gulf of Mexico will readily feed on the heavy fractions left and degrade them.’
Prof Geoffrey Maitland, Professor of Energy Engineering, Imperial College London and spokesperson for Royal Academy of Engineers, said:
’This is very much in line with my own recent estimates and statements — that about 25% has been captured or burned, 25% vaporised due to the light nature of the oil or naturally bio/photo-degraded already. Another 25% finely dispersed by either waves/winds/tropical storms or dispersants, and either at or close to surface and ripe for degradation fairly quickly, leaving just 25% washed ashore as either oil, water-oil emulsion or tar balls, which will need further mechanical treatment and removal (with minimal use of chemicals if they are sensible… Despite what the EPA have said the non-biodegradable dispersants, which may hang around much longer than the oil and do adsorb on fish gills and other marine-life organs causing life-threatening problems, are in my mind a bigger longer-term environmental concern) but should be a manageable task in the months ahead.
’So, without minimising the extent of the damage caused by this 25%, 1.25M barrels, the combination of boom containments, skimming, good luck with winds and weather and partial collection and eventual capping of the well on July 15th have all combined to make the short-term damage far less than people feared and the prognosis for a relatively rapid natural clean-up good with the prospect of fishing, shrimping and natural habitats returning to close to normal on a timescale from months to 1-2 years max. The light oil and the warm temperatures of the Gulf of Mexico make this prognosis much better than was the case on the Exxon Valdez in cold Alaska for instance, with which comparisons have been drawn. The effect on oiling and deaths of birds has been similarly light compared with the Valdez and expectations (less than 2000 in each case — wind farms are more of a threat); the effect on marine life breeding will need to be seen in time — many sea turtle eggs have been rescued and relocated to hatch, and the fishing embargo will have enabled some re-stocking to counter some of the depletion caused by the oil/dispersants, but the long term effects will not be known for some time.
’So it is encouraging to see government agencies and reports confirming this more encouraging picture. US Government Energy Advisor Caroline Browner confirmed all this in an ABC interview today. So although Tony Haywood was not right to say that the spill was a drop in the ocean and the environmental impact would be very, very modest, in the way that he did, the facts behind these ill-advised comments are turning out to be reasonably consistent with their underlying sentiments and sub-text. Although the latest figures confirm that this is indeed the biggest offshore oil spill ever, about 75% of the 200M gallons has been prevented from causing major damage and the environmental impact has not turned out to be anywhere near as bad as was feared in the first month or so of this crisis, with various conditions combining to give a reasonably optimistic prognosis for a reasonably rapid natural clean-up of months to 1-2 years.’