The Minerals Management Service says 19 moored drilling rigs and another nine jack-up drilling rigs experienced what regulators called "total failure of station-keeping ability" after hurricanes Ivan, Katrina and Rita blew through the Gulf.
"I think people were surprised how those could move or drift," said Red Cavaney, president of the American Petroleum Institute.
Working with the industry, regulators devised new standards affecting mooring designs, foundations, even the amount of air space between the surface of the water and a drilling rig platform.
Bud Danenberger, chief of offshore regulatory programs for the Minerals Management Service, said about a third of the targeted rigs meet the new standards and about half will be compliant by the end of this hurricane season.
Offshore oil rigs shown on map from here. Katrina path shown in red.