11.   It has also acquired some Canadian shipyards to augment its ability to build and upgrade offshore rigs.

12.   LaFrance was working for a contractor on a Shell Oil Co. offshore rig.

13.   Mobil Corp. began returning evacuated crews to its offshore rigs in the Gulf.

14.   Mossgas, a government-owned offshore rig and refinery that converts natural gas into gasoline and diesel fuel, is considered a boondoggle.

15.   Natural gas prices fell as Hurricane Opal veered away from platforms in the Gulf of Mexico, easing concern the storm would damage the offshore rigs.

16.   Now demand exceeds the worldwide supply of suitable offshore rigs.

17.   Offshore drilling rigs are often evacuated when a big storm approaches, and meteorologists recently upped their estimates for hurricanes this year.

18.   Oil rig makers are enjoying a growth in demand on the back of an increase in oil exploration in the region and the scrapping of older offshore drilling rigs.

19.   Oil and gas exploration is also booming, and Caterpillar sells engines that power offshore rigs and compressors that gather, store and pump gas through pipelines.

20.   Semi-submersibles are the most common type of offshore drilling rig.