A U.S. Coast Guard team yesterday sealed off six hatches of a grounded barge that had spilled some 50,000 gallons of home heating oil into Long Island Sound. Another barge and two oil tankers also are aground on the Atlantic coast.

A Coast Guard spokesman said a special strike team boarded the Bouchard 100 at dawn at Huntington, N.Y., and successfully closed six of the barges' seven hatches. They hoped to pump the remainder of the one million gallons of oil and gasoline from the barge.

At the mouth of Port Everglades, Fla., four tug boats and a Coast Guard cutter tried at high tide yesterday to dislodge a 638-foot oil tanker stuck on a sand bar. They were unable to budge the SS Exxon Chester with its 180,000 barrel crude oil cargo.

High winds and waves yesterday also delayed efforts to refloat the 918-foot tanker Tulsa Getty, aground in the mouth of the Delaware Bay with 922,000 barrels of oil aboard. The Coast Guard said there was no danger of an oil spill or of damage to the vessel, resting on the sandy bottom 13 miles west of Cape May, N.J.

At Havre de Grace, Md., the Coast Guard made plans to lighten a barge which ran aground in the Chesapeake Bay by removing some of the 50,000 gallons of heating oil carried by the vessel.