Big noises going on out yonder


Dynamically stabilized oil drilling and production platform.Dynamically stabilized oil drilling and production platform.

With much of the offshore noise attention being focused on seismic airgun surveys, other aspects of the fossil fuel industry’s contribution to ocean noise pollution may be sneaking by our review – noises which may have even greater impacts on marine life.

A few weeks ago a colleague in the industry sent us some information and specifications on dynamically stabilized exploration and production platforms used in deepwater operations. In water over a couple of thousand feet deep it becomes impractical to build a platform rigidly connected to the sea floor, so floating platforms are used. If drilling is to occur (as it does in the oil business) the platform needs to be stable and not subject to waves, wind, and swells. In lieu of steel towers and tethers these deepwater operations use drillships or floating production platforms.

These are remarkable vessels that may look like ships or like traditional oil derricks, but they are capable of stabilizing their working position in 70 mph winds and 30 foot swells. This takes a huge amount of energy, delivered to six 6,700 horsepower propeller-driven thrusters. And depending on the sea state they can be churning really hard. This is akin to having six supertankers all driving into each other – continuously, around the clock, 365 days per year. (The Marine Mammal Protection Act specifies an exposure threshold of 120dB re:1µPa for continuous noise. It is highly likely that these vessels exceed this under any sea state above World Meteorological Organization “WMO 4”.)

Granted, with 70 mph winds and 30’ swells the ocean is not whisper-quiet. But under most weather conditions these vessels will be a significant contributor to ocean noise. This is something that should be accounted for and regulated if the noise exceeds established noise exposure thresholds.

It should also be accounted for when weighing the true cost of a fossil-fuel driven economy.