Just two days after Hurricane Dennis plowed into the Gulf Coast, oil and gas producers Tuesday restarted scores of platforms in the Gulf of Mexico that were evacuated as the storm approached.

According to the U.S. Minerals Management Service, 64 platforms were shuttered at midday Tuesday, down from 359 on Monday when 1.4 million barrels, or 96 percent of the Gulf's normal daily oil production, was interrupted.

By Tuesday, the amount of normal daily oil production that was being kept off market had dropped to 57 percent, or 857,975 barrels, the MMS said. The Gulf produces about 1.5 million barrels per day from 819 staffed platforms.

Since the pre-Dennis evacuations began Friday, 4 million barrels of oil production have been shut in, about 0.9 percent of the Gulf's annual production of 547.5 million barrels, the MMS said.

The impact of Dennis was not as bad as some traders originally anticipated. Last year's sweep of Hurricane Ivan through the Gulf left behind damaged production platforms and caused others to shut down for months. Almost 44 million barrels of oil production were lost between September 2004 and February 2005 because of Ivan-related damage.

BP PLC reported that its Thunder Horse platform, located 150 miles southeast of New Orleans in about 6,000 feet of water, was listing between 20 and 30 degrees. The Thunder Horse field is being developed and is not yet producing petroleum. Exxon Mobil Corp. is a partner on the Thunder Horse project.

The platform had been evacuated Friday in anticipation of the storm and the damage was discovered Monday by a passing vessel, BP said.

Crews restored power to the platform on Tuesday and were expected to pump water out of the floating legs that keep the platform upright, said Chief Warrant Officer Adam Wine of the U.S. Coast Guard in New Orleans. Wine said the Coast Guard was monitoring the work and keeping other vessels away from the platform.

The industry was keeping a close eye on developing tropical storm Emily. The storm was forecast to be near Puerto Rico by Friday and could approach the U.S. mainland early next week, the National Hurricane Center said.

On Tuesday, shuttered production platforms kept 4.3 billion cubic feet of the Gulf's normal daily production of 10 billion cubic feet of natural gas from the market. On Monday, 6.2 billion cubic feet were shut in, the MMS said.

Since Friday, 22.4 billion cubic feet of gas have been delayed, the MMS said. The Gulf normally produces 3.65 trillion cubic feet of gas annually.

The Thunder Horse platform, 150 miles southeast of New Orleans, lists after the storm. The site isn't producing oil yet.