Some can afford to wait. Some can't.

Shell Oil is not taking any chances. Especially with a hurricane churning in the Gulf of Mexico.

At sea, employees gather their belongings and get on board a chopper bound for shore.

On Friday, another 200 non-essential employees got a quick trip across the gulf to Scholls Airport in Galveston.

Seventy-five others came Thursday and nearly 200 the day before that due to Tropical Storm Erin.

Chevron is moving some workers from its deep-water rigs, but production is still on line.

ExxonMobil, BP and Valero Energy all say they are monitoring Dean, but no evacuations yet.

In all there are more than 800 rigs running in the Gulf. Most of them relatively close to shore.

There is plenty of impact from a storm in the Gulf even if the rigs don't take a direct hit.

For example, the Magnolia rig was shut down for 20 days after Hurricane Rita in 2005. That's 20 days of no production and in a tight market, you know what that means.

Higher prices at the gas pump.

But it not just in the Gulf the refining sector is monitoring.

ConocoPhillps says that it has redundant systems in Oklahoma that can essentially relocate its entire corporate headquarters if necessary.

It is Magnolia Rig in the Gulf is still fully staffed, but as Dean gets closer expect the hum of helicopters to be a constant this weekend.