Okay. I’ve wanted to write about the Oil Spill that happened in the Gulf of Mexico for days now, but haven’t had the time or energy to write it well. So here it goes:
Firstly, I have worked in the Gulf of Mexico as an oceanographer and specifically worked installing and maintaining a current measurement system for the Deepwater Horizon rig when it was pretty much at the location where it exploded and sank. So I’ve spent some weeks on the DH and also some time in Venice Louisiana where the oil is striking land presently.
Incident
The actual incidence is fairly well understood now that the rig had pretty much finished the well and was in the process of recovering the drill tool and getting ready to fill the well hole with concrete to plug it for the months or years till it was to be used by BP as a production well. A pocket of Methane or possibly H2S gas escaped from the well and rose through the riser drill pipe. This would normally have been stopped by the lubricating drill mud which fills the riser, but this was either removed or at low pressure because the drilling had stopped. All oil rigs have different zones which define what type of electrical devices can be used these are (simplified) save zone and hazardous zone. Where the hazardous zones are where such gasses can expect to accumulate from time to time and thus the equipment there are designed to avoid electrical or mechanical sparks, heat sources or spaces where gas can collect. However with this incident, the gas bubble was so large that it engulfed the whole rig including the safe zones where equipment is normal as we would have in our homes maybe. At some point there was a spark which ignited the gas which apparently blew up all the gas in the drill pipe which acted like a bomb and took out the rig structure and also the pontoon floats which keep the rig on the surface. It was at this point the rig started to list and people were evacuated. I would have expected the whole team who were working the drill floor to have lost their lives in the initial explosion, while I am relived that the majority of people were saved!
The BOP
The Blow Out Preventor sits on the seabed and is often around the size of 2 x Hummer cars on top of one another. They are basically a funnel which the drill pipe enters to start to drill in the seabed. It has the benefits of having a shut off failsafe which would stop any of the above gas pockets or a sudden push of oil from rising up the drill pipe to the rig drill deck. However, in this case the BOP failsafe did not trigger and the gas escaped. There is discussion that the unit did not have an accoustic trigger too. I can't comment on that, however I hear that it was well maintained and was owned by Transocean and supplied by Cameron. This is very likley to be the issue when the whole issue comes to court..
The Oil
The itself is a fairly light weight oil compared to the thicker crude which is found in the North Sea or Alaska for example. It would therefore be more mobile in the water and more effected by currents but also by detergents and biodegradation.
Oil would normally degrade going through numerous stages where the chemical components change. Other people know far more about this than me, however I am aware that the changes are good as the further down this process, the less oil there is which can cause damage and the closer to biologically usable oil the spill would become. The best place for these changes would be at sea where the action of waves, currents, wind and biological activity would speed this up. If the oil reaches beaches and coastline, it often attaches to the sediment found there where it stops or reduces the changes and you might get longer term pollution for example 10 – 20 years of damage is possible. It is therefore important to keep the oil from shore and at sea. It is also good news when bad weather or seas occur as these would aid the dissipation.
The currents and waves
The currents in the gulf are fairly small for the most part and often the sea can be totally flat with barely a ripple. Which is great for a fishing and pleasure sailing industry. However a major current is called the Loop Current which generally enters the gulf as an eddy from the Gulf Stream and moves anti clockwise around the gulf. It is a warm core eddy which rotates clockwise, if you can picture a clockwise rotating piece of water which is moving in an anticlockwise movement around the gulf.
So what this would mean for the oil is that it is being dragged generally towards the Western end of the gulf, but locally it is being spread along the north and eastern coastline too. This is pretty bad for the oil spill defence as more coastline will be effected and it is plausible that the entire coastline of the gulf will be covered. I think it is unlikely that the East Coast of the states outside of the gulf would actually be affected, but the oil really needs to be kept away from shore.
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