Hurricane Isaac pummeled the U.S. Gulf Coast on Wednesday, flooding levees in low-lying parishes near where oil and gas producers and refiners have shut in operations, seven years to the day after Hurricane Katrina.
The Category 1 hurricane made first landfall on Tuesday evening, retreated, and moved back inland early Wednesday, packing 80 miles-per-hour winds.
Energy firms were waiting for the storm to pass before they can restart shut-in offshore production and oil refineries.
The U.S. Department of Energy estimated about 936,000 barrels per day or 12 percent of oil refining capacity had come offline on the Gulf Coast.
The U.S. Bureau of Safety and Environmental Enforcement said that 93.28 percent of oil and 66.7 percent of natural gas production was disrupted by the hurricane in the Gulf.
The Gulf of Mexico accounts for about 23 percent of U.S. oil production and 7 percent of natural gas output, according to the U.S. Energy Information Administration. About 30 percent of U.S. natural gas processing plant capacity and 44 percent of the country's oil refining capacity also line the Gulf Coast, the EIA said.