What’s the Difference Between an Oil Spill And a Natural Gas Spill?

Throughout the day on Tuesday, Hercules 265, a drilling rig in the Gulf of Mexico, was evacuated, after a blowout from the natural gas well it was digging made it too dangerous for workers to stay. At the end of the day Tuesday, the rig caught fire, and yesterday the platform started to collapse. The underwater natural gas well is leaking, says the Associated Press, and stemming the flow could take weeks.

With the memories of the 2010 Deepwater Horizon disaster still fresh in many people’s minds, it’s hard not to make comparisons. But, for what it’s worth, says the Associated Press, authorities are assuring that this current leak will be nowhere near as bad as that from the BP spill. For one, the Hercules platform fire is in relatively shallow water, which should make it easier to deal with. The AP:

“A gas well’s not going to result in any kind of major pollution — perhaps not even significant pollution if it’s burning,” said Ted Bourgoyne, the former chair of Louisiana State University’s petroleum engineering department. He now runs the consultancy Bourgoyne Enterprises Inc.

Federal inspectors said a light sheen was spotted around the rig on Wednesday evening, though authorities said it quickly dissipated and the fire aboard the rig continued to be fed by natural gas. A sheen was spotted shortly after the blowout began on Tuesday but it, too, quickly dissipated.

Gas wells often also have oil or other hydrocarbons as well as natural gas. Officials and scientists agree the latest mishap shouldn’t be nearly as damaging as the BP oil spill that famously sent crude oil oozing ashore in 2010.

Natural gas, says NPR, isn’t as bad as oil because, unlike oil, natural gas and water do mix. Natural gas also evaporates. If the gas is leaking from the sea floor—as opposed to from the platform—then it is possible that “gas could be flowing into the ocean,” says NPR:

But natural gas is mostly made up of methane, and in deep wells, the methane would most likely dissolve before it gets to the surface.

“Once dissolved, it’s eaten by bacteria. “Methane is the best thing they can eat,”  Patzek says.

In the Deepwater Horizon accident, lots of natural gas as well as oil escaped into the water before the Macondo well was capped. Scientists determined that methane-eating microbes degraded much of that gas without evidence of serious harm to the environment.

And, of course, natural gas is easier to deal with than oil, since it doesn’t float on the surface and foul beaches or animals.

But while natural gas may be less visible than oil, that doesn’t also mean it is harmless. Oil spills cause a number of very obvious effects on the landscape: Oil tends to stick around as tar balls or to get spread as a thick coating on coastal wildlife. Sea birds caked with oil are an iconic image, as are dead dolphins.

The consequences of a natural gas spill can still be dire, says Russian toxicologist Stanislav Patin in the synopsis to his 1999 book Environmental Impact of the Offshore Oil and Gas Industry. Following a leak, says Patin,

Gas rapidly penetrates into (especially through the gills) and disturbs the main functional systems (respiration, nervous system, blood formation, enzyme activity, and others). External evidence of these disturbances includes a number of common symptoms mainly of behavioral nature (e.g., fish excitement, increased activity, scattering in the water). The interval between the moment of fish contact with the gas and the first symptoms of poisoning (latent period) is relatively short.

Further exposure leads to chronic poisoning.

And, the warm, oxygen depleted waters in the Gulf of Mexico could make it worse: “ Numerous studies show that the oxygen deficit directly controls the rate of fish metabolism and decreases their resistance to many organic and inorganic poisons,” says Patin.

So, this might not be the 2010 Deepwater Horizon oil spill disaster, one of the most signficant oil spills of all time, but a natural gas leak can still be dangerous for the local ecosystem–especially if the leaking well is not swiftly brought under control.

More from Smithsonian.com:

How Scientists Know the Tar Balls Hurricane Isaac Dredged Up Came From the BP Oil Spill
Oil Spill Finally Confirmed as a Culprit in Dolphin Deaths

Colin Schultz | | READ MORE

Colin Schultz is a freelance science writer and editor based in Toronto, Canada. He blogs for Smart News and contributes to the American Geophysical Union. He has a B.Sc. in physical science and philosophy, and a M.A. in journalism.