UPDATE 3-Storm Debby shifts east, may miss U.S. Gulf oil patch

* Nearly quarter of oil, gas in Gulf shut -U.S.

* BP shuts all production; Conoco, Shell shuts some platforms

* LOOP halts tanker offloadings due to storm (Updates with latest NHC forecast)

HOUSTON, June 24 (Reuters) - Tropical Storm Debby appeared headed away from the U.S. offshore oil patch o n S unday, according to U.S. forecasters, after threatening to cut a swath through the main oil and natural gas production areas.

The storm's threat alone had led oil and gas producers to shut nearly a quarter of production from the region that accounts for about 20 percent of the nation's oil production and about 6 percent of natural gas output.

"There has been a significant change in the forecast track" of Debby, the U.S. National Hurricane Center in Miami said late on Sunday.

The NHC called the Sunday afternoon forecast a "low-confidence" projection that the sprawling Debby would move toward the Florida panhandle and away from offshore production areas off the coasts of Louisiana and Texas.

Earlier NHC forecasts had pointed the storm toward Texas or Louisiana.

BP Plc, the largest oil producer in the Gulf of Mexico, shut in all of its production.

The Louisiana Offshore Oil Port, the only U.S. port that can receive the largest oil tank ships, stopped operating due to rough seas.

ConocoPhillips and Royal Dutch Shell Plc had also shut some of their production as of Sunday as the first storm of the 2012 Atlantic hurricane season to threaten offshore production gained strength in the Gulf.

As of midday on Sunday, 22.7 percent of daily crude oil production, up from 7.8 percent on Saturday, and 22.9 percent of daily natural gas output, up from 8.16 percent, had been shut due to Debby, according to the U.S. Bureau of Safety and Environmental Enforcement, which oversees oil and gas activity in the Gulf. (Reporting by Erwin Seba; Editing by Maureen Bavdek, Marguerita Choy and Dale Hudson)