By Robert Campbell

NEW YORK, Aug 17 (Reuters) - Oil and gas companies operating in the Gulf of Mexico stepped up evacuations of workers Friday for the first Atlantic hurricane of 2007, which some forecasts say could hit refining hubs on the U.S. Gulf Coast next week.

Hurricane Dean, which could strengthen to a powerful Category 4 storm over the next two days, is currently expected to strike the northeast tip of Mexico's Yucatan peninsula on Tuesday before entering the Gulf of Mexico, the U.S. National Hurricane Center said Friday.

But some of the hurricane forecast models tracked by Reuters showed the storm passing between the Yucatan and Cuba and moving towards the Texas coast between the oil refining hubs of Corpus Christi and Houston.

Many companies said they were waiting for the various hurricane forecasts to fall into line before implementing their storm preparedness plans.

"We will implement any contingency plans probably next week when we get a better handle on Dean's path," said ConocoPhillips spokesman Bill Tanner.

Conoco's Sweeny, Texas, refinery is located northeast of Corpus Christi and is far enough inland that it is unlikely to be seriously affected if a storm hits there, Tanner said.

Of more immediate concern for energy companies was offshore oil and gas platforms and mobile drilling rigs.

Drilling contractor Transocean Inc. <RIG.N> and Murphy Oil Corp. <MUR.N> said they had already evacuated dozens of workers from offshore facilities. Other companies said they were making preparations to evacuate workers if necessary.

"We are also closely watching Hurricane Dean and are preparing to take action depending on its movement," said Royal Dutch Shell Plc <RDSa.L>, one of the largest oil and gas producers in the U.S. Gulf of Mexico, on its Web site.

As of Thursday, 13 oil and gas platforms and five drilling rigs in Federal waters had been evacuated, according to the Minerals Management Service, which oversees oil and gas production in Federal waters.

Less than 2,600 bpd of oil production and 10.5 million cubic feet per day of gas output had been affected by the closures, which were implemented ahead of the arrival of Tropical Storm Erin on Thursday, the MMS said.

(Additional reporting by Matthew Robinson, Janet McGurty and Robert Gibbons)

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