Exxon Mobil Corp evacuated non-essential workers from the Lena production platform in the Gulf of Mexico ahead of Subtropical Storm Alberto, the company said on Sunday.
Royal Dutch Shell Plc and Chevron Corp shut production on platforms in the eastern Gulf of Mexico due to Alberto and evacuated workers from those sites, the companies said.
The U.S. National Hurricane Center said Alberto was transitioning to a tropical cyclone as its circulation became more focused around a central core located 135 miles (220 km) west of Tampa, Florida, with 50 mile per hour winds (85 kph).
The storm was expected to make landfall on Monday morning in the Florida panhandle.
Chevron shut production at its Blind Faith and Petronius platforms in the eastern Gulf. The Blind Faith platform is located in the Mississippi Canyon region of the northern Gulf of Mexico.
The Petronius platform is in the Viosca Knoll area of the Gulf.
Shell shut its Ram Powell Hub, which is also in the Viosca Knoll area, on Friday.
Shell has shut the production platform at the Appomattox Hub it is developing in Norphlet in the eastern Gulf. Appomattox has not yet begun production, but the platform recently arrived on the site.
Exxon said production in the Gulf was unaffected by the evacuations and the company transferred control of its offhsore operations in Mobile Bay, Alabama, to an onshore control room.
The Gulf of Mexico is home to 17 percent of daily U.S. crude output and five percent of natural gas output, according to the U.S. Energy Information Administration.
More than 45 percent of the U.S. refining capacity and 51 percent of natural gas processing capacity is located along the Gulf.