* Visund gas leaked for nearly 5 hours due faulty riser
* Riser inspections had shut Visund and Njord fields
* Visund and Njord field jointly produce 120,000 boed
(Adds gas leak stopped, caused by riser trouble)
By Wojciech Moskwa
OSLO, April 9 (Reuters) - Norwegian oil and gas producer Statoil ASA (STL.OL) said it had stopped a gas leak from a riser at the Visund field in the North Sea and was bringing back evacuated personnel back to the platform on Saturday.
The incident happened a day after Statoil announced that it was investigating internal damage to flexible risers -- or the pipes that carry oil and gas from the seabed to the platform, and that it had shut production at Visund and the Njord field.
Statoil said the gas leaked for nearly five hours on Saturday and was “believed to have started at a point in a fixed riser carrying oil and gas” from a well to the Visund platform.
Statoil earlier said it had evacuated about half of its 123 platform employees from Visund, leaving only emergency staff.
“Evacuated personnel will be returned to the platform ... The situation at Visund will now be gradually normalised,” Statoil said in a statement, adding that nobody was injured.
Statoil was not immediately available for further comment.
Along with the shutdown of Visund, Statoil said late on Friday that it had also suspended production on its Njord field in the Norwegian Sea on April 1, due to riser concerns.
It said that faults were discovered in some of the Njord A platform risers in the autumn of 2010, triggering inspections.
“The current challenges are limited to a specific type of riser technology,” Statoil said in a statement late on Friday, which also played down the risks of leaks.
“Internal damage of this type does not threaten the structural integrity of the risers, but over time it will reduce resistance to leakage,” Statoil added in its Friday statement.
Njord produces some 70,000 barrels of oil equivalent per day (boed) and Visund produces about 50,000 boed.
“The inspection is still in progress, and the production will be phased in as the risers have been inspected and approved,” Statoil said.
Statoil said “equivalent risers” were also in use on other installations on the Norwegian shelf including its Veslefrikk, Snorre A and B, Norne, Aasgard A and B and Glitne fields.
“On these installations, however, the risers are connected to a pipeline system on the seabed which reduces the risk of damage. There have been no known incidents or observations ... that suggest damage to risers here,” Statoil said on Friday.
Statoil is also the operator of Njord and has a 20 percent stake. German utility giant E.ON Ruhrgas [EONR.UL] has 30 percent, France’s GDF Suez GSZ.PA 20 percent, Exxon Mobil Corp (XOM.N) 20 percent, Petoro 7.5 percent and VNG [VNG.UL] 2.5 percent. (Editing by Susan Fenton)