Science of oil rigs: surviving Gulf storms

It had partially collapsed during hurricane Dennis - just four months after US Interior Secretary Gale Norton declared in a dedication ceremony that it was an "anchor of energy stability," designed to "withstand the worst that winds and waves will throw against it."

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The tipping of Thunder Horse, weighing more than 50,000 tons and capable of drilling in waters up to 6,000 feet deep, points up just how vulnerable the industry is to powerful storms - even with the most advanced technology.

But so far this season, offshore oil production has continued relatively unaffected.

That's in part because the storms have not been as damaging as in past years. But it also has much to do with lessons learned from last year's hurricane Ivan, which tore through the Gulf damaging more than 30 drilling platforms and shutting down 83 percent of oil production at its peak.

Big-risk industry

That storm is unlikely to be repeated, experts say, but it usefully revealed the strengths and weaknesses of the growing US offshore industry, currently accounting for a quarter of US energy production.

And since that September storm, perhaps the biggest to wreak havoc on infrastructure in the Gulf, oil companies have been working overtime to make sure their structures can survive even the most severe storm.

It's an especially important issue since the Gulf is in a cycle of higher storm activity that began a decade ago and could continue for years, according to the National Oceanic and Atmospheric Administration.

The most recent hurricane to threaten the Gulf oil industry was Emily. Before landfall, more than 15,000 offshore workers on 112 US oil rigs and platforms were evacuated.

Currently, the number of US structures in the Gulf is roughly 4,000, with 819 manned platforms. And those numbers are only expected to grow, says Caryl Fagot, a spokeswoman for the federal Minerals Management Service (MMS), which regulates the oil industry in federal waters.

"History shows us progressing further and further offshore as technology improves," she says.

MMS figures show that 94 exploratory wells were completed in the deep-water Gulf last year, up from 74 in 2003.

There are many reasons behind this boom in offshore oil production, says John Felmy, chief economist at the American Petroleum Institute in Washington.

"We've drilled a lot of holes in the rest of the continental US. That, coupled with real limitations to onshore areas and the development of incredible deep-water technology is making the Gulf a tremendous opportunity right now," he says.

This week, his organization will be co-sponsoring the Offshore Hurricane Readiness and Recovery Conference in Houston. The conference will bring together industry, academic, and regulatory experts to discuss lessons learned from hurricane Ivan.

What hurricane Ivan revealed

In May, the MMS commissioned six studies on everything from Ivan's impact on platforms and rigs to its effect on underwater pipelines.

Rick Mercier has been overseeing the Offshore Technology Research Center's work at Texas A&M University in College Station. They have been commissioned to study rig fastening on offshore platforms, and their initial findings show a need for better moorings.

During Ivan, for instance, drilling units were hauled onto platforms and did quite a bit of damage during the storm because they were not properly secured. That particular problem has since been addressed. In addition, all rigs and platforms must now be equipped with a GPS device since several rigs went missing for a day or two after Ivan.

But the most lasting damage was done to hundreds of pipelines brought down by mudslides during hurricane Ivan. While not much can be done to prevent mudslides, more can be done to speed up repairs, research is showing.

Still, Dr. Mercier was pleased with how well platforms performed during hurricane Ivan. "The deep-water technology was designed to withstand 100-year conditions and, at times, we saw 1,000-year conditions out there," he said. "That's a pretty strong validation of our technology."

Floating mammoths

Indeed, the industry has been operating in the Gulf since 1947 and has plenty of experience handling such storms - though experts agree that technology has improved dramatically in recent years.

Take Thunder Horse, for instance, the $5 billion semisubmersible platform 150 miles southeast of New Orleans. It is about 50 percent larger than the next largest such rig in the world and includes more than 100 technical firsts that will enable it to process 250,000 barrels of oil and 200,000 million cubic feet of natural gas per day - enough to supply 6.5 million American homes with energy.

It is one of only 30 floating platforms in the world and stays upright through a complex system of ballast tanks that pump water back and forth. It is held in position by 16 mooring lines anchored to the sea floor.

And while it was tipping 20 percent after hurricane Dennis, MMS findings have shown that rigs built before 1978 with lower decks and weaker joints are more susceptible to powerful storms.

During hurricane Andrew in 1992, for instance, 22 mostly older oil structures were felled as opposed to the seven structures during hurricane Ivan. But while much is being learned about how to keep structures sound in storms, some say it is simply part of the high-risk business.

"It's a hostile environment and hurricanes are just one of the things the industry has to live with," says Mark Baxter, director of the Maguire Energy Institute at Southern Methodist University in Dallas.