Advertising

Thursday, September 22, 2005 - Page updated at 12:00 AM

E-mail article     Print

Close-up

Oil platforms: built to last?

Newhouse News Service

MOBILE, Ala. —

In the days after Hurricane Katrina, as hundreds of oil-producing platforms remained offline — and some continued to leave a conspicuous trail of petroleum in the Gulf of Mexico — federal officials insisted to Congress that they were doing everything possible to make this critical infrastructure stable during hurricanes, designing platforms to withstand Category 5 storms.

But federal and industry documents obtained by the Mobile Register show that the most-recent design criteria for offshore oil and natural-gas platforms require only that these structures withstand winds and seas typical of a borderline Category 2/Category 3 storm, well below the Category 4 and 5 winds that affected Gulf oil fields at least four times in the past five years.

The implications of these design decisions extend beyond the oil-drilling industry and include the gasoline price spikes in the days after Katrina, and the spreading oil slicks emanating from multiple platforms in the Gulf.

Federal officials on Tuesday released reports of at least 64 spills associated with Gulf platforms after Katrina.

"For these platforms and other critical facilities, I'm really surprised that people would put that type of investment out there without more consideration," said Lawrence Twisdale, an expert in hurricane impacts and risk assessments for Applied Research Associates in Raleigh, N.C.

In the past year, three hurricanes with sustained winds of 140 mph or greater — Ivan, Dennis and Katrina — have damaged Gulf platforms. According to a Shell Web site, Ivan destroyed seven platforms in September 2004 and damaged 26. Katrina destroyed at least 46 platforms last month and significantly damaged an additional 16, according to the American Petroleum Institute.

Many other platforms could not operate after Katrina because of pipeline ruptures and other problems throughout offshore oil fields.

Katrina, along with current closures in anticipation of Hurricane Rita, shut 1.1 million barrels, or 73 percent, of daily crude-oil output in the region, according to a report yesterday from the U.S. Minerals Management Service, which manages offshore resources. That was almost 15 percentage points more than the previous day.

On Sept. 6, Rebecca Watson, the Interior Department's assistant secretary for Land and Minerals Management, told Congress that "current design standards require industry to design facilities to Category 5 storm criteria."

But the Register found that federal regulations require that facilities be designed to withstand a 100-year storm as defined by the American Petroleum Institute, a nonprofit trade organization.

In the documents used to calculate design loads for offshore platforms — called API 2A-LRFD and API 2A-WSD — the institute defines a 100-year storm in the northwestern Gulf of Mexico as having 80-knot one-hour average winds. According to Twisdale and wind engineers from Texas Tech University, that should be equivalent to about 115 mph in sustained one-minute winds, the scale used to gauge hurricane strength.

In wind estimates provided by ConocoPhillips, three-second wind gusts produced by the institute's 100-year storm would be 134 mph. Such gusts typically are associated with one-minute sustained winds of about 109 mph, according to standard calculations used by the American Society of Civil Engineers.

This means the wind-design standards for the offshore structures approximate an upper Category 2 or lower Category 3 hurricane (110 mph is the threshold between Category 2 and Category 3; 130 mph is the Category 3/Category 4 threshold).

Although engineers working with industry and the U.S. Minerals Management Service have described Ivan and Katrina as once-in-1,000-year events, other engineers who have worked with hurricanes say such storms are not so unusual.

Twisdale said his researchers at Applied Research Associates are analyzing the data, but their preliminary estimates indicate the wind field associated with Katrina was not a once-in-a-1,000-year event, but rather in the range of a once-in-a-100-year event.

That's the kind of storm the industry and federal officials say they are preparing for in the Gulf. But Katrina's Category 4 or 5 winds were far in excess of Petroleum Institute standards, and so were the waves produced by the storm.

The Petroleum Institute's standards require that platforms be built to survive waves of up to about 70 feet high.

During Katrina, one federal data buoy recorded a "significant wave height" of more than 55 feet about 80 miles east of the hurricane eye, according to Christopher Burr, chief of tropical analysis for the National Hurricane Center.

Significant wave height is a way of measuring the average of the highest waves, but Burr said it is safe to assume that some individual waves were more than 100 feet high.

Burr noted that researchers at the Naval Research Laboratory recorded a 91-foot wave more than 100 miles from the eye of Hurricane Ivan. Those researchers estimated that waves closer to the eye were in the range of 131 feet.

Minerals Management Service spokesman Gary Strasburg said the agency's view is that such waves are not typical. "My understanding with that is that is an anomaly," he said Monday. "It is not something that would be expected, that high wave."

Burr said such waves are not out of the ordinary for major hurricanes. "It's been known for quite some time," he said. "It's just getting more press recently."

Even a Category 3 storm, under the right conditions, can produce waves close to 100 feet, Burr said.

American Petroleum Institute officials said they couldn't comment on the standards, and referred questions to the Minerals Management Service, whose officials defended Watson's assessment that the government requires that platforms be built to Category 5 standards.

"I'm confident that the Category 5 is the design criteria in our regulations," said Tom Readinger, an economist and associate director of the offshore minerals-management program for the federal agency. "It's design, and you can quote me."

Standards in agency regulations "are based on a facility surviving a Category 5," Readinger said, adding that he would have to consult with engineers before he could find the specific reference to Category 5 conditions in the federal regulations.

In a subsequent interview, Strasburg said the wording in the standards referred to a 100-year storm, not a Category 5 storm. He said the primary intent of the standards was to protect against large waves, not simply high winds.

"The reason we used the Cat 5 terminology is that a Category 5 storm could generate those waves," Strasburg said. But, he acknowledged, "so could a Category 3 or a Category 4."

Copyright © 2005 The Seattle Times Company

advertising


Get home delivery today!

Advertising