Oil and natural gas operators that work in the Gulf of Mexico (GOM) and along the Gulf Coast were beginning assessments of their facilities now that Isaac has been downgraded to a tropical storm, officials said Wednesday.

The National Hurricane Center (NHC) downgraded the Category 1 storm around midday, although Isaac continued to soak southeastern Louisiana and southern Mississippi with heavy rains and wind. Dangerous coastal storm surge and inland flood threats were expected until Thursday morning.

Isaac, whose maximum sustained winds had fallen to about 70 mph, was moving toward the northwest at about 6 mph and that track was forecast to continue until Thursday, when it then is seen turning toward the north-northwest Thursday night or early Friday. Southern Arkansas should be prepared for Isaac's heavy rains early Friday.

Oil and natural gas personnel should begin returning to the GOM once flyover inspections of offshore facilities are completed, officials said.

GOM mobile offshore drilling units (MODU) were keeping station, and dynamically positioned drilling rigs that were moved off-location prior to the storm were accounted for, according to staff with the Bureau of Safety Environmental Enforcement (BSEE). MODUs include both jackup and moored drilling rigs.

"The team will continue to work with offshore operators and other state and federal agencies until operations return to normal and the storm is no longer a threat to Gulf of Mexico oil and gas activities," the Department of Interior arm said.

Based on data from offshore operator reports submitted as of 11:30 a.m. CDT Wednesday the BSEE estimated that about 71.64% (3.224 Bcf/d) of the current daily natural gas production, and 94.72% (1.307 million b/d) of daily oil output in the GOM was shut-in.

Personnel had been evacuated from 505 of the 596 manned production platforms, equivalent to 84.73% of the total platforms in the GOM. Fifty of the 76 rigs, or about two-thirds, also remained evacuated.

"After the hurricane has passed, facilities will be inspected," said BSEE staff. "Once all standard checks have been completed, production from undamaged facilities will be brought back on line immediately. Facilities sustaining damage may take longer to bring back on line."

Producers expect flyover inspections of offshore facilities, as well as personnel redeployment, to take several days.

The Houston-based arm of Royal Dutch Shell plc said it would begin flyover inspections of assets in the central and eastern GOM on Thursday. If conditions were considered safe, the company planned to begin redeploying staff to those areas Friday. An Apache Corp. spokesman said Friday likely was the earliest offshore personnel would go back to work.

BP plc, which is one of the biggest producers in the GOM, said Wednesday its offshore personnel remained evacuated from its operated production platforms and rigs and all of its output from the offshore remained temporarily shut in. Oil processing facilities in Port Fourchon and Houma, LA, as well as in Pascagoula, MS, also remained closed.

"We will continue to keep a close eye on the storm to determine when conditions are safe to redeploy personnel and resume operations," said BP spokesman Brett Clanton. "However, we cannot yet predict when that will be."

Chevron Corp. spokesman Russell Johnson said, "When it is safe to do so, Chevron will begin to deploy personnel to its onshore and offshore facilities to assess the effect of the storm. We will not comment on any possible impact to operations."

Anadarko Petroleum Corp., which operates the natural gas Independence Hub among other things, also has kept its offshore personnel onshore for now. The shut-in deepwater facilities continue to include the hub, along with the Constitution, Marco Polo, Red Hawk, Neptune and Gunnison.

"In total approximately 195 personnel were safely removed from our operations in the Gulf," said an Anadarko spokesman. "We continue to monitor the track of Hurricane Isaac and will only return our workers and restart production when it is safe to do so..."

Williams, whose Williams Partners LP operates a long list of gas processing and pipeline facilities along the Gulf Coast and in the GOM, said its offshore and onshore assets in the western GOM were operating normally.

However, the Devils Tower, Canyon Station and Blind Faith platforms remained shuttered, and the offshore Mountaineer and Canyon Chief gathering pipelines were shut in and secured. In addition, Williams said the onshore Mobile Bay gas processor and Geismar olefins plant are closed, and the onshore Larose and Paradis facilities, which are part of the Discovery system, remained shut in.

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