WHEN an offshore well stops producing oil, what should be done with the rig? One option is tohaul it ashore, break it up and recycle it. This is expensive. For a big, deep-water oil or gasplatform, it can cost $200m. Just hiring a derrick barge massive enough to do the job cancost $700,000 a day. But there is an alternative: simply leave most of the structure where itis. That is what you would expect a greedy oil firm to do: despoil the ocean just to save a lousyfew million dollars. The surprise is, the cheap option may actually be greener.
For a start, it takes a lot of energy to move a rig. The ships that would be needed to shiftCalifornia's largest one would emit 29,400 tonnes of carbon dioxide, by one estimate. Andmoving a rig disturbs the organisms that have attached themselves to its underside, or jacket.Far better, some say, to turn old rigs into coral reefs.
“Reefing” typically involves bringing a platform's above-water parts ashore and cropping thelower parts to leave at least 26m of clearance: deep enough for ships to pass over, yet shallowenough for photosynthesis to nourish organisms on its upper reaches (see picture). Oil-rigreefs may shelter and feed up to eight tonnes of fish. In 2009 Shell moved a jacket in the Gulfof Mexico ten kilometres (six miles) away. The fish followed.
More than 490 platforms in American waters have become reefs in the past three decades. Thefederal Bureau of Safety and Environmental Enforcement urges states to issue reefing permits.State coffers gain: oil firms typically hand over half the money they save by reefing.
Those savings vary greatly. Small platforms in shallow waters can often be removed for $10m,but sometimes for as little as $1m, according to DecomWorld, a consultancy. But for stateswith lots of offshore oil rigs, the windfalls soon add up. Mississippi pocketed an average of$625,000 for each of the 12 permits it has issued, according to Melissa Scallan of the state'sDepartment of Marine Resources. Louisiana's take has averaged $270,000 per reefing—and thestate has seen 336 of them, says Mike McDonough of the Louisiana Department of Wildlife andFisheries.
Currently, less than a tenth of America's old oil and gas platforms are reefed. Sometimes thereasons for this are practical. For example, platforms may be removed if waiting for a permitmeans weathering another hurricane season (in 2005 150 defunct platforms in the Gulf ofMexico were toppled by winds and waves). Operators typically favour reefing but it is not alwayseconomical or allowed, says David Welch of Stone Energy Corporation. The firm has onlyreefed 12 of the 60 Gulf of Mexico platforms it has decommissioned.
That share is likely to grow. Within five years oil firms will be reefing one offshore rig in four,predicts Quenton Dokken of the Gulf of Mexico Foundation, a conservation group. Gulf states,particularly Louisiana and Texas, are making “a big push” to streamline the permitting process,he says.
Far bigger savings are possible in the deep waters off California. Four years ago the GoldenState passed a law allowing reefing. Operators are loth to estimate costs publicly, but theTulane University Energy Institute reckons that reefing the state's 27 platforms could save $2billion. A platform or two could be retired as early as next year, though rising oil prices maymean they keep pumping longer.
The California Ocean Science Trust, a research group that has advised lawmakers, thinks thatplatforms increase marine life and should not all be removed. Skyli McAfee, the group'sdirector, describes this conclusion as “a big fat duh”. Studies by Milton Love, a marinebiologist at the University of California, Santa Barbara, support it. Oil platforms serve as“excellent nursery grounds” that boost fish populations, he says. The bocaccio, a rockfishwhose numbers are worrying fishing authorities, is one big beneficiary.
Yet the odds of preserving most oil-rig reefs look bleak. Public opposition is robust. Not oneplatform off California has been reefed. Activists quote the findings of scientists such as JamesCowan, an oceanographer at Louisiana State University, who studied isotopes, tissue caloricdensities and the stomach contents of creatures from both natural and artificial reefs andconcluded that the latter generate no extra biomass. The Environmental Defence Centre inSanta Barbara, a group that files anti-development lawsuits, advocates the complete removal ofoil platforms. Linda Krop, its chief counsel, says that abandoned structures might damageanchors, rob natural reefs of fish and even leach poisons. She does, however, acknowledgethe environmental damage associated with complete removal.
Greenpeace, a pressure group, makes a different argument. John Hocevar, its head of oceancampaigns, concedes that in some locations reefed platforms, if non-toxic, may increase marinelife. But they should be banned anyway, he says, because they save the oil firms money andtherefore encourage them to drill more.
The debate is likely to intensify. In the Gulf of Mexico some 400 platforms are now beingdecommissioned each year. Divers and many fishermen want more to be reefed; shrimperscomplain that reefs prevent them from dragging nets across parts of the ocean floor. InCalifornia operators must decide quickly if they wish to turn redundant rigs into reefs. Until2017 firms can keep 45% of the savings. After that the figure falls to 35% until 2023; then itdrops to just 20%.