Deepwater Horizon


later – those who underwent the crash course during the previous episode are not around or available anymore.


The scientific literature doesn’t help much either. Most studies undertaken when the cash was there are never completed with the scientific rigour that referees and editors of scientific magazines require, so the reports end up in the so call ‘grey’ literature, where they are difficult to track and reclaim many years later. In connection with the Deepwater Horizon oil spill, BP promised to support research and studies of oil in the Gulf with US$500 million – a gigantic sum in this context. Thus, other types of funding organisations like research councils see no urgency to use their limited and much in demand resources in the oil spill field. Then it turns out that the scientists who accept BP funding cannot publish their results until the legal procedures following the spill are concluded. At that time in the future, the scientists who perform the studies with BP funding will have to convince the gatekeepers to the scientific press that their studies are unbiased and not designed to give the results the financier likes to see. They may find it hard to do so. Thus, the next time – and let’s hope it won’t happen soon – there is a major oil spill in the Mexican Gulf, the lessons might have to be learned again.


What, then, are the crucial lessons? The first has to do with how oil behaves on and in water. Crude oil spilt on the surface will first spread out and, while doing so, lighter components as well as entrapped gas will evaporate and the more water-soluble fractions will dissolve from underneath. If the water is still and the sun is blazing, photo-oxidation will start to alter the chemical composition, e.g. by breaking double bonds. Gradually, and much quicker in turbid waters, droplets of water will enter the oil, the character and colour of which will change to what is called ‘chocolate mousse’. The oil–water emulsion will now have a density not too different from that of seawater and thus be almost as much in as on the water. When the water content reaches a certain critical point, the emulsion will be one of oil droplets in water instead of water droplets in oil. It will now be suspended in the water and evaporation will forthwith be of little importance, while the huge surface area of the oil droplets will speed up the dissolution process.


Given the scarcity of reports and, even when reported, the lack of reliable quantification, no clear figures can be given of the total global extent of pipeline discharges.


On the surface of the oil drops, particles will attach including bacteria, some of which can degrade oil components. The sum of these physical, chemical and biological processes will lead to the residue consisting more and more of heavy fractions of the crude, like asphaltenes, which through gravity will sink and eventually reach the sea floor sediments.


Oil from a blowout, if injected into seawater under high pressure at the ocean floor, will behave differently. It will quickly become a three-phase emulsion with oil, water droplets and methane gas bubbles, that in addition mostly contains mineral particles. Some part


EXPLORATION & PRODUCTION – VOLUME 9 ISSUE 2


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