The U.S. government says 78 percent of the oil production in the Gulf of Mexico has been halted in preparation for Tropical Storm Isaac.
The Bureau of Safety and Environmental Enforcement reports about 1 million barrels per day of oil production has been stopped as companies have evacuated 346 offshore oil and gas production platforms. That's 17 percent of daily U.S. oil production and 6 percent of consumption.
The agency says 2 billion cubic feet of natural gas production is also affected. That's about 3 percent of daily U.S. production and consumption.
Production is expected to quickly resume after the storm passes. The price of U.S. benchmark crude oil fell 68 cents to $95.47 per barrel. Natural gas fell 5 cents to $2.65 per 1,000 cubic feet.
Some evacuated rig workers were brought to Scholes Airport in Galveston. The helicopters used to shuttle the workers will be parked at the airport to keep them out of the storm's path.
"High winds, debris flying off. Some of the helicopters can be completely destroyed by the hurricanes. So they have to get them out of harm's way," said Hud Hopkins, the Scholes Airport director.
Gas prices can spike during a time of less oil production, officials say.
"Already it's gone by up a dollar. So I expect it to go up for the next day or two. So, we're already talking 3 or 4 dollars. I expect it to be around that," said Satish Nagarajaiah, a professor at Rice University.