HOUSTON (Reuters) – Royal Dutch Shell and Anadarko Petroleum announced production shut-ins affecting five Gulf of Mexico oil platforms on Wednesday ahead of a storm expected to lash the Texas coast with heavy winds and rain later this week.

The U.S. National Hurricane Center issued a hurricane watch Wednesday for much of the Texas coast, calling for slow-moving Tropical Depression Harvey to intensify as it nears landfall.

Texas Governor Greg Abbott declared a state of disaster for 30 counties ahead of the storm.

Between 10 inches and 15 inches (25 cm to 38 cm) of rain are expected from the central Texas Coast to southwest Louisiana, with some areas receiving up to 20 inches of rain, according to the Miami-based NHC.

“Heavy rainfall is likely to spread across portions of eastern Texas, Louisiana, and the lower Mississippi Valley from Friday through early next week and could cause life-threatening flooding,” the NHC said in an advisory.

In Corpus Christi, city officials warned residents to expect a storm surge of between four feet and six feet (1.83 m) and began distributing sand bags to local residents.

The U.S. Gulf of Mexico is home to about 17 percent of the nation’s crude output and 5 percent of dry natural gas output, according to the U.S. Energy Information Administration. More than 45 percent of the nation’s refining capacity is along the U.S. Gulf Coast.

Shell said it was evacuating all personnel from the roughly 100,000 barrel per day Perdido oil and gas production platform as a precaution. Anadarko said it had shut in production and was evacuating workers from its Boomvang, Gunnison, Lucius and Nansen platforms in the Gulf of Mexico.

Other Gulf of Mexico operators said they were watching developments closely but operations were unaffected.

Chevron on Wednesday afternoon said it had not evacuated any staff and BP Plc said normal operations were still underway. ConocoPhillips said it was making preparations but had not interrupted any operations.

Tropical Depression Harvey, which had top sustained winds of about 35 miles (55 km) per hour as it churned over Mexico’s Bay of Campeche late Wednesday, could become a hurricane by Friday, the NHC said.