By the end of the day, more than 700 offshore platforms and rigs had been evacuated, two rigs had drifted away and authorities in Alabama were forced to close a bridge over the Mobile River after it was struck by a runaway platform. Oil futures briefly climbed above $70 a barrel for the first time.
The hurricane's economic tally has barely begun, but effects are bound to ripple across the country.
Home to as much as a quarter of oil and gas production in the United States, the Gulf Coast is also the site of five of the nation's dozen busiest ports. The region's refiners produce about 45 percent of U.S. gasoline.
The area's impact goes way beyond energy, too.
The Port of South Louisiana alone handles 15 percent of all U.S. exports.
In a just-in-time economy, those facilities are crucial nerve centers that tie the Mississippi River Delta to the world economy.
''Anytime you have a transportation supply disruption, there are going to be ripple effects,'' said John Robertson, a senior economist at the Federal Reserve Bank of Atlanta.
''The longer the disruption, the more significant it is.''
With the fallout still unknown Monday, economists could only guess on the storm's commercial impact.
The powerful hurricane roiled the energy industry at a time when producers worldwide were already struggling to keep up with strong demand, and it threatened to constrain the supply of home heating fuels this winter. The rise in energy prices has already slowed the U.S. economy's growth rate, though domestic fuel consumption is still rising.
The Bush administration said it would consider lending oil from the nation's emergency stockpile to refiners that request it - Citgo Petroleum Corp. asked for 250,000-500,000 barrels to ensure its Lake Charles, La., refinery does not run out - and the president of OPEC said he will propose a production increase of 500,000 barrels a day at the cartel's meeting next month. Analysts nervously awaited details on the extent of the damage to the region's platforms, pipelines, refineries and electric grid.
''We're losing a lot of crude oil and also a lot of natural gas,'' said Lawrence Goldstein, president of the New York-based nonprofit Petroleum Industry Research Foundation. Goldstein estimated that total refinery production of gasoline, heating oil, diesel and other fuels could fall by as much as 20 million barrels over the next 60 days.
Royal Dutch Shell PLC said on its Web site that two of its drilling rigs equipped with tracking devices had ''drifted off location.'' The company said it would send aircraft to check the status of its assets ''as soon as it is safe to do so.''
Also Monday, several refiners said damage at their plants appeared to be minimal and oil prices eased from the day's high of $70.80 a barrel. But if a bleaker picture emerges in the days ahead - it may take more time to assess damage, depending on how rough the seas are - prices could run-up once again, analysts said.
Based on conversations with oil and gas companies operating in the Gulf, Goldstein said it appeared that Katrina would not curb output for as long as last year's Hurricane Ivan, even though the short-term impact was significant.
The federal Minerals Management Service said Monday that 92 percent of the region's oil output was shut-in, or shut down, with more than 3 million barrels of production lost since Friday. The agency said 83 percent of natural gas output was shut-in, resulting in a loss of 15.5 billion cubic feet of lost production since Friday.
The Gulf of Mexico normally produces 2 million barrels of crude oil a day, or about 35 percent of the United States' domestic output, according to government and industry data. About 10 billion cubic feet a day of natural gas is produced in the region.
Wholesale gasoline prices in the New York and Gulf Coast markets soared by 25-35 cents a gallon on Monday following reports that more than 8 percent of U.S. refining capacity had been shut down as a precaution ahead of the storm.
One analyst said pump prices nationwide would likely average more than $2.75 a gallon by week's end - up from $2.61 a gallon last week, according to Energy Department data released Monday.
''Unfortunately, I don't think $3 a gallon is a hyperbolic number in some markets anymore,'' said analyst Tom Kloza of Wall, N.J.-based Oil Price Information Service. He emphasized that the market reaction is a reflection of supply tightness, not shortages. Natural gas futures briefly surged more than 20 percent after the temporary closure of a critical distribution hub and on concerns that power outages and flooding could prevent processors from running their plants for days, if not weeks.
Even before Katrina arrived, the Energy Department had warned consumers who rely on natural gas to heat their homes to expect sharply higher bills this winter.
Mississippi refineries:
Chevron USA Inc., Pascagoula, Miss., 325,000*
Ergon Refining Inc., Vicksburg, Miss., 23,000
Hunt Southland Refining Co., Sandersville, Miss., 11,000
Hunt Southland Refining Co. Lumberton, Miss., 5,800
Louisiana refineries:
Exxon Mobil Refining & Supply Co., Baton Rouge, La., 494,000*
Citgo Petroleum Corp., Lake Charles, La., 425,000
Valero Saint Charles Refinery, Norco, La., 260,000*
Motiva Enterprises LLC, Convent, La., 255,000*
ConocoPhillips, Belle, Chasse, La., 247,000*
Marathon Ashland Petroleum LLC, Garyville, La., 245,000*
Motiva Enterprises LLC, Norco, La., 242,000*
ConocoPhillips, Westlake, La., 239,400
Chalmette Refining LLC, Chalmette, La., 187,200*
Murphy Oil USA Inc., Meraux, La., 125,000*
Valero Refining Co., Krotz Springs, La., 80,000
Shell Chem LP, Saint Rose, La., 55,000
Placid Refining Co., Port Allen, La., 48,500
Calumet Shreveport LLC, Shreveport, La., 35,000
Calcasieu Refining Co., Lake Charles, La., 30,000
Calumet Lubricants Co. LP, Cotton Valley, La., 13,020
Calumet Lubricants Co. LP, Princeton, La., 8,300
Alabama refineries:
Shell Chem LP, Saraland, Ala., 80,000
Hunt Refining Co., Tuscaloosa, Ala., 33,500
Gulf Atlantic Refining & Marketing, Mobile, Ala., 22,000
