Oil and Gas leaks from Deepwater Horizon

When the oil and gas leaked from the Macondo Well at Deepwater Horizon oil rig in the Gulf of Mexico in June 2010 something happened that never happened before. The oil and gas leaked some one and a half kilometres under the sea.

Scientists are familiar with the environmental effects of oil and gas spillages at or near the surface of the sea. The chemicals contained in the oil and gas – hydrocarbons, benzenes and naphthalene are volatile and when they reach the surface are rapidly lost to the atmosphere in a matter of hours of days. The sea may be clogged with surface oil but this can be cleaned, swept from beaches and gathered. The hydrocarbons and other chemicals do not stay in the sea.

Altogether the Federal authorities in the United States estimate that 4.1 million barrels of oil. It is estimated that the gas released at Macondo was 1600 cubic feet of gas for every barrel of oil released. The gas was 82% methane, the rest being made up of mostly ethane and propane.

What seems to have happened with the Macondo well leak is that most of the heavier and relatively insoluble petroleum components were transported to the surface or deposited on the ocean floor. We do not know the proportion of the heavier oil that went up or stayed down.

The lighter water soluble hydrocarbons were dissolved in the water and stay dissolved in the water. They are unlikely to be released into the atmosphere and we do not understand the effect of these dissolved hydrocarbons on the ocean environment.

As oil and gas becomes scarcer and as the price of oil and gas rises exploration companies are looking for oil and gas in remote places. Much of the exploration and eventual production of oil and gas will come from deep water at a mile or more from the surface of the sea. It is impossible to obtain oil from the surface or close to the shore without leaks of oil and gas. It will be impossible to drill a mile or more under the sea without losing millions more barrels of oil and millions of cubit feet of gas which will dissolve in the sea.

The sea is a vast place, but it is not infinite. At some stage the effects of the dissolved hydrocarbons in the sea will be such that they will change the sea, and the change will not be for the better.

You can see the scientific analysis at http://www.pnas.org/content/early/2011/07/15/1101242108.full.pdf+html

 

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