*

Shell, Chevron ( CVX ) removing some staff from offshore platforms

*

Rafael forecast to become category 2 hurricane at mid-week

(Adds Chevron removing staff from offshore in paragraph 5)

HOUSTON, Nov 4 (Reuters) - A late season tropical storm

predicted to intensify into a category 2 hurricane in the U.S.

Gulf of Mexico this week could reduce U.S. oil production by

about 4 million barrels, researchers said.

Storm Rafael was in the Caribbean Sea late on Monday and

expected to enter the Gulf of Mexico on a track that takes it

through prime oil-producing areas. Winds could reach 100 miles

per hour (161 kph) on Wednesday, the National Hurricane Center

said.

U.S. oil producers could lose between 3.1 million and 4.9

million barrels of oil, said energy analytics firm Earth Science

Associates using a model that estimates volume losses to past

storm intensity and track.

Natural gas production losses could range between 4.56

billion and 6.39 billion cubic feet, according to its model. The

upper end assumes structural damage that prolongs shut-ins, said

Tony Dupont, Earth Science's chief operating officer.

Shell and Chevron ( CVX ) on Monday said they were

moving non-essential personnel to shore from several platforms

ahead of the storm. Shell said it was pausing some drilling

activity but there was impact on production. Chevron ( CVX ) also said

routine oil and gas production was not affected.

Earth Science's model calls for Rafael to have the

second-largest impact of this year's storms on offshore

production, behind hurricane Francine, which shut in up to 42%

of oil and 52% of natural gas production.

Raphael, the 17th named storm of the Atlantic hurricane

season, is on a track would take it through areas of the Gulf

that are heavy with oil and gas platforms. The season runs

through Nov. 30.

There have been 10 named Atlantic storms formed this year

since September 24, a record for the period, according to

Colorado State University meteorologist Phil Klotzbach.