Royal Dutch Shell said an aerial inspection of its giant Mars oil and gas platform indicated some damage to its upper deck. Two of its drilling rigs were also adrift.
At least six other drilling companies, including Ensco and Transocean , reported rigs adrift after the storm, raising the prospect that dragging anchors or moorings might tear apart vital sub-sea pipelines.
Newfield Exploration Co. said it had lost one of its production platforms in the eastern Gulf.
On the refining side, a U.S. senator who flew over southeastern Louisiana on Tuesday said three facilities belonging to Murphy Oil and Exxon Mobil were all "under water." Flooding is a serious risk for refineries.
Valero Energy Corp. said its 250,000 bpd refinery near New Orleans did not incur serious damage and should be operating again in two weeks. A total of nine refineries were shut down and four more were running at reduced rates.
There was some good news from offshore operators, as Kerr McGee resumed oil and natural gas production at two facilities in the western U.S. Gulf while BP and Marathon Oil said early assessments showed no damage.
The Louisiana Offshore Oil Port, which handles a tenth of U.S. crude imports, also said initial damage reports were encouraging and hoped to begin crude shipments on Thursday.