* Nyhamna can export up to 20 pct of Britain's gas needs
* Plant's ownership could rise to 13 firms from five
* Shell set to relinquish operatorship to Gassco
By Lefteris Karagiannopoulos
OSLO, March 17 (Reuters) - The ownership of Norway's Nyhamna gas-processing plant, a major supplier of energy to Britain, could expand to 13 companies this year from five now when Gassco succeeds Royal Dutch Shell as the facility's operator, Shell told Reuters.
Currently processing gas from the offshore Ormen Lange field, Nyhamna will also receive gas from Statoil's Aasta Hansteen and other fields from late 2018 via the new Polarled pipeline.
The plant exports gas to Britain via the Langeled pipeline, which can meet about 20 percent of Britain's gas needs.
A new ownership structure will reflect the addition of more gas input sources, allowing the Polarled owners to take stakes in the plant, Gassco said.
"We can confirm that the Nyhamna gas plant will become part of a new joint venture," said a Gassco spokeswoman, declining to comment on how the ownership will be split.
Gassco said Shell was expected to remain technical service provider (TSP) at Nyhamna, meaning the company will continue to handle daily operations, similar to the TSP role Statoil plays at the Gassco-operated Kaarstoe and Kollsnes gas plants.
"Shell is one of 13 parties with future ownership interests," Shell said in an email to Reuters, declining to elaborate further on the process.
The Nyhamna plant is currently owned by Ormen Lange license partners Norway's Petoro, Statoil, Shell, Denmark's DONG Energy and ExxonMobil.
Potential future owners include France's Total, Wintershall, the oil and gas subsidiary of Germany's BASF, Italy's Edison, ConocoPhillips and Austria's OMV.
Norway's oil and energy ministry must approve the new ownership structure and set gas transportation tariffs that will ultimately impact the profitability of the pipelines and processing system.
"The decision (on tariffs) will be made before start-up of operations of the new facilities ... after a proposal is sent on public consultation," a ministry spokesman said. (Additional reporting by Nerijus Adomaitis; Editing by Terje Solsvik and Dale Hudson)