By America Hernandez and Christoph Steitz

PARIS/FRANKFURT, Jan 7 (Reuters) - Austria's OMV has struck a deal to supply Germany's Uniper with gas from its Black Sea project from 2027, three people familiar with the matter told Reuters, as Europe seeks new ways to boost energy security after cutting ties with Russia.

The five-year deal for 15 terawatt hours of natural gas from the Neptun Deep project, which has not previously been disclosed, comes after Russia last month stopped delivering gas via Ukraine and a broader winding down of European Union energy purchases from Moscow due to its invasion of Ukraine.

The total contract volume represents about 1.5% of Germany's gas imports in 2024 and would be the first deal underpinning the long-awaited deepwater project, more than a decade after gas was first discovered in Romania's section of the Black Sea.

Neptun Deep, which is expected to start producing in 2027, holds an estimated 100 billion cubic meters (bcm) of recoverable gas, making it one of the EU's most significant natural gas deposits.

Once it comes online, Romania will become the EU's largest gas producer and a net gas exporter for the first time.

OMV Petrom , which is majority-owned by OMV

with Romania holding a 20.7% stake, first announced it had discovered 42-84 bcm of gas in the Black Sea in 2012.

Uniper declined to comment. Both OMV and OMV Petrom did not respond to a request for comment.

OMV Petrom and state-owned producer Romgaz , which own the Neptun Deep project in a 50:50 split, approved the project in 2023.

Production at the plateau will be about 8 bcm annually for about 10 years, nearly doubling Romania's gas output.

The producers plan to sell the gas separately, but under a Romanian law the government will have a pre-emptive first right to gas from the project.

Gas producers have said there is huge potential for further discoveries in Romania's Black Sea, where the country has an estimated 200 bcm of reserves that promise to help diversify supply in the region.

($1 = 0.9614 euros)

(Reporting by America Hernandez in Paris, Christoph Steitz in Frankfurt and Luiza Ilie in Bucharest. Editing by Mark Potter)

((america.hernandez@thomsonreuters.com; +33623014155))