HOUSTON, July 6 (Reuters) - The U.S. Coast Guard warned

of possible Texas port closures from Corpus Christi to Houston

and began restricting vessel traffic because of Tropical Storm

Beryl, which is expected to become a hurricane before making

landfall by Monday morning at Port Lavaca.

Port closures could bring to a temporary halt shipments of

crude oil to refineries and motor fuels from those plants.

Port condition "Yankee" was set by the Coast Guard captain

of the port of Corpus Christi on Saturday afternoon, restricting

vessel movement in ports from Matagorda Bay, 101 miles (163 km)

southwest of Houston, to the U.S.-Mexico border.

Citgo Petroleum Corp was cutting production at its 165,000

barrel-per-day Corpus Christi, Texas, refinery on Saturday ahead

of the approach of Beryl to the Texas coast.

Citgo plans to keep the Corpus Christi refinery running

at minimum production as the storm moves up the coast toward a

projected landfall at Port Lavaca, a pipeline hub.

Oil producer Shell Plc ( SHEL ) completed the evacuation

of workers from its Perdido production platform in the

U.S.-regulated Gulf of Mexico ahead of the approach of the

storm, the company said on Friday night.

Production on Perdido was shut prior to the evacuations.

Shell said it also evacuated workers from the Whale platform,

which is due to start production later this year.

Gibson Energy ( GBNXF ), which operates a large oil terminal

in Corpus Christi, said operations were continuing, but it would

take further steps depending on the forecast.

The storm was moving on Saturday with maximum sustained

winds near 60 mph (95 kmh), the National Hurricane Center said.

The latest forecasts would put Corpus Christi on the dry

side of the storm where the lowest winds and least rain could be

expected. But Beryl could bring gale-force winds to the port,

which is why the Coast Guard restricts traffic or shuts the

port.

Most of the northern Gulf's offshore oil and gas production

is east of Beryl's forecast track.

U.S. Gulf of Mexico offshore production of about 1.8 million

barrels per day accounts for about 14% of total U.S. crude

output, according to the U.S. Energy Information Administration.

Any impact on supplies could push up prices of U.S. oil and

offshore crude grades.

Oil major Chevron Corp ( CVX ), among the biggest U.S.

offshore producers, said on Friday that production from its

operated assets remained normal. But it evacuated nonessential

personnel from some of its Gulf of Mexico facilities.

Murphy Oil Corp ( MUR ) said it has not shut in production

or evacuated personnel, and continues to monitor the storm.