The US Bureau of Safety and Environmental Enforcement, which oversees oil and gas activity in the basin, said 313,775 barrels per day of oil and 1.031m cubic feet per day of gas was shut in as operators evacuated installations and shut down operations ahead of the storm.
The Gulf accounts for about 20 per cent of US oil production and nine per cent of natural gas output.
BP, the largest oil producer in the Gulf of Mexico, said it was shutting in all of its oil and gas offshore platforms, and Royal Dutch Shell stopped production on some of its platforms and was preparing for further shutdowns in the central and western Gulf.
Other producers were performing evacuations of workers from the Gulf.
Debby is expected to hit southeast Louisiana by sometime Wednesday as a hurricane.