A spokesman for Leipzig-based VNG said the transaction was roughly worth $150 million. An agreement was signed on Thursday with the Norwegian firm's parent company in Houston, Endeavour International Corp, he said.
The deal was subject to approval by energy, finance and cartel authorities, VNG said.
Endeavour, based in Oslo, holds 21 licences and is project leader in several exploration ventures, allowing VNG to participate in producing fields for the first time, VNG said.
Both companies have been cooperating in several fields in the last few years via VNG's office in Stavanger, Norway.
VNG sold 165.2 billion kilowatt hours of gas, mainly procured from Russia, in 2007 and has not released a figure for 2008.
A statement from the Endeavour group said the sale frees up finance for the company to focus on Britain and the United States instead.
It also said the approval procedures were expected to be completed within 60 days.
VNG's peer Wintershall bought Norwegian Revus last year to improve its activities there.
The Norwegian oil and gas sector is still dominated by Statoil ST.OL but the government will be issuing acreage to outsiders in its coming 20th licencing round.