Adds background on Norway production, detail of project in paragraphs 2, 6, 8-9

OSLO, June 19 (Reuters) - Equinor EQNR.OL and its partners will invest just over 4 billion Norwegian crowns ($410 million) in a new subsea development that will boost gas production from Norway's offshore Troll field, the company said on Friday.

Norway is Europe's biggest supplier of natural gas, meeting around 30% of the continent's annual demand, and the North Sea Troll field is its largest gas resource.

The TWIN project agreed with partners Petoro, Shell SHEL.L, TotalEnergies TTEF.PA and ConocoPhillips is expected to contribute a total of around 11 billion standard cubic metres of gas from Troll, Equinor said in a statement.

The companies aim to start production from the new development as early as 2028, said Gunnar Nakken, Equinor's senior vice president for projects and subsea in Norway.

"By simplifying, increasing standardisation, and reusing existing infrastructure and equipment, we are reducing costs and enabling faster production in line with our new ways of working," Nakken said in the statement.

PROJECT IS THIRD STAGE OF TROLL PHASE 3

It was not immediately clear how much the project could contribute on a daily or annual basis, and the company did not immediately respond to a request for additional comment.

The TWIN project, consisting of two wells in a seabed template and a pipeline connected to existing subsea facilities, is the third step of Troll phase 3, which produces gas from the Troll West reservoir, Equinor said.

It follows the announcement last month that Norway's petroleum safety regulator had given Equinor permission to start gas production from the now completed second phase of Troll phase 3.

Operator Equinor owns a 30.55% stake in Troll, while state company Petoro holds 55.93%, Shell 8.19%, TotalEnergies 3.69% and ConocoPhillips 1.64%.

($1 = 9.7534 Norwegian crowns)