Geology & Geophysics Research Spotlight

The Fate of Hydrocarbons Seeping from the Ocean Floor

Researchers investigate the properties of bubbles at deep-ocean oil seeps to improve oil spill models.

Source: Journal of Geophysical Research: Oceans

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In April 2010, an explosion on the Deepwater Horizon oil rig, which sits approximately 64 kilometers off the coast of Louisiana in the Gulf of Mexico, caused the largest marine oil spill in history. Over the following 83 days, the blowout released more than 4 million barrels of hydrocarbons directly into the surrounding water.

Before the devastating Deepwater Horizon accident, oil spill prediction models did not focus much on the dissolution of liquid oil droplets. Noting that dissolved oil could have toxic effects on marine ecosystems, Wang et al. investigated the transport and ultimate dissolution of hydrocarbons released from natural seeps in the ocean by monitoring the bubbles from two natural seeps near the Deepwater Horizon site in real time with high-speed, stereoscopic cameras. These cameras were mounted on Hercules, a remotely operated vehicle transported aboard the Exploration Vessel Nautilus, during a July 2014 cruise.

A research overview can be seen in the video below:

The scientists observed two types of bubbles: smaller bubbles that were much more spherical in size and larger bubbles that were darker in color, more elongated or misshapen, and thought to contain oil. Using high-speed cameras, they also could observe an icelike hydrate skin that formed on the bubble surface. On average, the bubbles were 3 to 4.5 millimeters in diameter. Bubbles traveled independently from each other in one of two ways: The fast-moving bubbles moved upward from the seep site in a helical trajectory; the second class of bubbles rose 40% slower in a zigzag pattern.

A view of fast-moving bubbles, including an explosive burst of methane, can be seen in the video below:

Observations from this study, the researchers say, give scientists a comprehensive view of bubble dynamics from seep flares. Because the behavior of the bubbles observed in the natural seeps could mirror the behavior of hydrocarbons released during oil spills, the findings will help investigators improve the predictive abilities of oil spill models. (Journal of Geophysical Research: Oceans, doi:10.1002/2015JC011452, 2016)

—Wudan Yan, Freelance Writer

Correction, 21 June 2016: This article has been updated to avoid the implication that the videos were collected during the July 2014 cruise specifically. Rather, they pertain to the broader research effort.

Citation: Yan, W. (2016), The fate of hydrocarbons seeping from the ocean floor, Eos, 97, doi:10.1029/2016EO054229. Published on 17 June 2016.
© 2016. The authors. CC BY-NC-ND 3.0