Oil companies continued to cease offshore operations and evacuate personnel on Thursday in preparation for Tropical Storm Harvey becoming a full-blown hurricane.

The tropical storm is expected to intensify into an category 3 hurricane by Friday morning, as it heads directly for the Texas and Louisiana Gulf Coast. If it reaches hurricane strength, Harvey would be the first hurricane to hit Texas in nearly a decade.

Oil firms Exxon Mobil, Shell, and Anadarko had begun shutting down their offshore operations Wednesday evening. An Exxon spokeswoman told the Washington Examiner that it continued to close its offshore and coastal operations through Thursday afternoon, while refineries on land continued normal operation.

"Exxon Mobil is closely monitoring Tropical Storm Harvey, and continues preparation for severe weather at its offshore and coastal operations in the Gulf of Mexico," said spokeswoman Suann Guthrie.

"We are in the process of evacuating all personnel from our facilities expected to be in the path of the storm, which includes the Hoover platform and Galveston 209 platform," she explained.

The Hoover platform was built to be the world's deepest offshore drilling platform at 4,800 feet and is named for the Hoover field that it extracts roughly 100,000 barrels a day of oil, along with equivalent amounts of natural gas.

Both the Hoover and Galveston 209 platforms are "shut in" in anticipation of the storm, said Guthrie. "Our Hadrian South subsea production system in the Gulf of Mexico is also shut in. Refineries are currently operating as normal."

Shell and Anadarko also shut in their offshore platform facilities. Anadarko said late Thursday afternoon that it has completed evacuation of all its facilities in the western Gulf, and stands ready to do the same in the eastern portion if the storm intensifies.

"We have safely removed all personnel and temporarily shut in production at our operated Boomvang, Gunnison, Lucius, and Nansen facilities, which are located in the western portion of the Gulf," Anadarko reported at 5 p.m. on Thursday. "These facilities will remain shut in until the hurricane has passed, and it is safe to return our people to these offshore locations. We will continue to track Harvey and are ready to remove additional personnel and shut in production at our operated facilities in the eastern portion of the Gulf, if necessary."

On-land operations were just suspended on Thursday, and ConocoPhillips announced it was stopping all drilling and fracking in the Eagle Ford shale field. Although another large firm, Apache, said it was taking precautions but does not plan to cease production.

As of Thursday, 9.5 percent of Gulf oil production has been shut in, or taken offline, because of the Harvey threat. That represents about 167,000 barrels per day, according to the Interior Department's Bureau of Safety and Environmental Enforcement. In addition, oil imports are also expected to fall over the next few days.

West Texas Intermediate crude oil prices had dropped in afternoon trading by 81 cents to $47.60 per barrel, while Brent crude oil future prices fell 41 cents, to land at $52.07 per barrel.

The White House said it is monitoring the situation along with the Department of Homeland Security, which houses the Federal Emergency Management Administration.