The company said its UK subsidiary has signed agreements for the acquisition of a portfolio of non-operated oil and gas assets in the UK Continental Shelf from the Italian major.
The deal will give JX Nippon stakes in 17 producing fields and some of the biggest developments planned in UK waters, including a near-30% interest in the Mariner heavy oil field east of Shetland.
While the price was not disclosed, JX Nippon said it will make a significant investment in the UKCS with the aim of quadrupling production by the end of the decade to around 40,000 – 50,000 barrels of oil equivalent per day.
David Nash, executive director at JX Nippon Exploration and Production UK, said: "JX Nippon's investment aims to consolidate the UK as an important profit centre for the JX Group in the long-term."
The acquisition is the latest in a series of bumper deals involving foreign owned companies that are buying North Sea assets to secure access to reserves amid strong demand for oil and gas.
On its website, JX Nippon says: "The UK North Sea is known as an area where the country risks and operational risks to invest in oil and gas are low due to stable local laws and regulations, including the tax regime.
"The UK North Sea is an area where relatively small oil and gas fields can be commercialised. Infrastructure for commercialisation is readily available."
The company said the tax breaks granted by the UK Government in recent months had been a big factor.
Mr Nash said: "A number of previous adverse tax changes made it very challenging to justify such a major investment, but through 2012 the collaborative approach that has been developed between industry and government has begun to ameliorate the situation.
"The introduction of field allowances and steps being taken by the Government to provide certainty on decommissioning tax relief contributed to our decision to finally proceed with this acquisition."
Malcolm Webb, chief executive of industry body Oil & Gas UK said the announcement by JX Nippon provided further evidence that recent changes are beginning to restore confidence among global investors in the province.
The Chancellor had sparked outrage by including a surprise hike in taxes in the 2011 Budget.
It is understood Eni regards the interests it is selling to JX Nippon as non-strategic but remains committed to UK assets like the Elgin-Franklin and MacCulloch developments.
Eni, which has extensive interests in countries such as Angola and Nigeria, has been active in the UK since 1964.
JX Nippon entered the UK North Sea in 1994 when its acquired interests in a range of licences from Petrofina. It has interests in more than 10 producing fields with more expected to come onstream within a few years.