OTTAWA, Aug. 22 — A 15-month standoff between the Canadian province of Newfoundland and Labrador and several major oil companies over an offshore oil project ended Wednesday, putting the $5.6 billion development back in motion.

Last year, the province’s premier, Danny Williams, walked away from talks with a consortium that includes Exxon Mobil and is led by Chevron Canada after the companies rejected his demands for an equity stake and additional royalties when oil prices are high.

On Wednesday Mr. Williams, a Conservative and a multimillionaire, announced that he now had an agreement that would give his province a 4.9 percent stake in the Hebron oil project for 110 million Canadian dollars ($103.8 million).

The tentative pact with the oil companies, he added, also includes an extra 6.5 percent royalty, on top of a 30 percent base rate, and removes the special investment tax credits that the oil industry had demanded.

“This is a happy day for the province,” Mr. Williams said by telephone from the provincial capital of St. John’s. “We’re entering into a whole new era.”

The deal largely fulfills Mr. Williams’s demands from 2006, with the exception of the addition of an oil-processing operation in the province.

Exactly what broke the impasse is unclear. James C. Bates, a vice president in charge of asset development at Chevron Canada, which is based in Calgary, Alberta, declined to comment on what had closed the gaps between the sides. Mr. Bates characterized the outcome as “a win-win situation.” The Hebron oil field contains an estimated 731 million barrels of oil. As with most energy projects in Canada, the vast majority of its production will most likely flow to the United States.

Some analysts estimate that construction may begin in 2010.

Hebron will be Newfoundland’s fourth offshore oil project. Mr. Williams said that given the agreement’s terms and expected high oil prices, Hebron would be unusually lucrative, generating about 16 billion Canadian dollars ($15.1 billion) for Newfoundland over 25 years as well as 7 billion Canadian dollars for the federal government.

Newfoundland struggled economically even before joining Canada in 1949. The collapse of cod stocks in recent years devastated its main industry, fishing and fish packing.

But Wade Locke, an economist at Memorial University in St. John’s, said that oil royalties and energy industry spending meant that Newfoundland would no longer qualify for financial assistance from the federal government by the end of 2009.

“Hebron, combined with everything else, will turn Newfoundland into a province of opportunity, like Alberta,” he said, referring to the affluent and oil-rich western province.

While Mr. Williams’s tough stand last year drew criticism from parts of Canada’s business community, it contributed to his party’s 75 percent approval rating among Newfoundland voters in opinion polls. The announcement of a Hebron agreement is expected to help sustain the Conservatives’ position as they head into an election in October.