There are around 6,000 oil rigs around the world. As the floating facilities go about the work of extracting oil and natural gas, their underwater substructures get turned into vertical reefs by marine plants and animals.
Researchers from the University of California Santa Barbara (UC Santa Barbara) compiled data from the fragmented and sparse scientific literature on converting oil platforms into permanent reefs.
They pointed out that an oil rig negatively affects the environment when it actively extracts and produces petroleum. If it suffers an accident, the resulting oil spill causes severe harm to marine animals and the local ecology.
At the same time, the rig also serves as a rich habitat for ocean life. Its provides a 3D reef for animals to call home while its open construction allows the passage of nutrient-rich water through its structure. (Related: EPA giving oil companies the OK to dump fracking chemicals into Gulf of Mexico.)
In 2014, the UC Santa Barbara researchers evaluated the biological productivity of marine habitats around the world. To their surprise, they found that oil rigs off the California coastline generate more benefits for fish than coral reefs or the Chesapeake Bay.
The stance on reefing oil rigs varies according to the country. Europeans prefer to restore the drilling site to its natural state, so they get rid of the entire platform.
On the other hand, American states on the Gulf of Mexico regularly turn old rigs into permanent reefs. The Gulf contains more than 500 sunken rigs, accounting for 11 percent of the decommissioned platforms on the American side.
While oil companies and local marine life receive the most benefits, the practice also gets support from some conservationists, fishermen, and state governments.
"In the Gulf of Mexico, when you go fishing, you motor up to a platform and tie directly to it," explained UC Santa Barbara researcher Ann Scarborough Bull, the author of the study. "There's a different societal thinking about the use and usefulness of parts of platforms that you don't have in California."
It takes a lot of money and effort to decommission an oil rig. Removing all of the California-based oil rigs from the seabed and transporting them elsewhere for disposal, for example, will cost $8 billion. The cost includes bringing the support structure to the shore and removing the thousands of tons of marine life that grew on the construction during its service life.
Transitioning a rig into an artificial reef is much cheaper and easier. The oil company removes all hydrocarbons and other hazardous materials in the lower portion of the platform. The company also pays part of the money it saves to the coastal state if the latter has a rig-to-reef law.
In exchange, the state gains a new reef and jurisdiction over the surrounding waters. If the area used to be federal waters, the state still assumes responsibility for charting its location and setting up warning buoys.
"Decisions are going to have to be made about more and more of these structures," explained MSI researcher Milton Love, the co-author of the study. "We want everyone to have the same facts as they go into the process so decisions can be made on a rational basis."