Sound science and common sense should guide discussions of energy exploration, development, and environmental stewardship, especially regarding efforts to find and produce the world’s offshore energy resources.
When it comes to seismic surveys – one of the critical tools used by the offshore industry – a welcome piece of good news was provided recently when the Obama administration rejected emotional appeals to ban the practice. Encouragingly, the regulators at the Bureau of Ocean Energy Management provided scientific justifications for their decision.
In seismic mapping, acoustic arrays towed behind ships send short, high-pressure pulses down to the sea floor about every 10 seconds. Hydrophones capture the sound waves that bounce back, providing tremendous volumes of data that give our scientists 3D images of what lies within the subsurface beneath the waves.
It’s a fascinating process, as this video from the International Association of Geophysical Contractors makes clear.
Click here if the video doesn’t play.
Under the watchful eye of government regulators, this technology has been used safely and successfully by industry for about a half century. And it’s worth pointing out that the U.S. Geological Survey currently is conducting its own seismic mapping off the east coast.
Setting the scientific record straight
But seismic mapping has its detractors.
A variety of anti-energy-industry activist groups, such as Oceana and Greenpeace, contend that the practice threatens whales and other marine mammals and should be prohibited. A favorite cry is that the noise from seismic surveying is 100,000 times more intense than a jet engine.
An arresting claim, but one that is not supported by science, as the federal government definitively stated this summer (and not for the first time, I’ll point out).
“A large air gun is loud, although it is not 100,000 times louder than a jet,” wrote William Brown, the chief environmental officer for the Bureau of Ocean Energy Management.
“Measured comparably in decibels, an air gun is about as loud as one jet taking off…. [Moreover] the higher density of water and higher speed of sound in water make sound in water less intense than sound in air.”
Brown’s statements were part of a public justification issued for a decision by the bureau regarding energy exploration activities along the Atlantic coast. Though the decision was necessarily limited in scope, the principles established there apply to all waters where energy exploration occurs.
No evidence of adverse effects
Seismic mapping is carefully regulated by governments around the world, most of which are rightly concerned with ensuring minimal disruption to marine mammal populations.
So is ExxonMobil. That’s why we go to great lengths to ensure that seismic mapping activities protect marine life and safeguard the environment.
That includes having marine mammal spotters onboard our ships when conducting surveys, which enables us to maintain safety zones for marine mammals during the entire survey period. Moreover, we employ a “soft start” technique in which acoustic arrays are started in slower sequence rather than all at once. This gives dolphins and whales that might be in the area ample opportunity to swim away from the gradually increasing sound levels.
These are among the reasons, as Mr. Brown made clear, there have has been “no documented scientific evidence of noise from air guns … adversely affecting marine animal populations or coastal communities.”
One place there is a lot of unhelpful noise is our policy debates, with opponents of energy development flooding the discussion with arguments based in emotion rather than facts and sound science. That’s the case whether the topic is energy exports, taxes, hydraulic fracturing , or offshore development. It’s heartening to see that when it comes to an essential component of offshore energy exploration like seismic surveys, arguments for sound science have risen above the din.