By Vegard Botterli
OSLO, Oct 4 (Reuters) - The evacuated Yme North Sea oil platform is at risk of collapse this winter, operator Talisman Energy warned safety authorities in a July letter seen by Reuters on Thursday.
Repairs were needed to avert such a risk, Talisman said in the letter to the Norway's Petroleum Safety Authority dated July 26, written several weeks after the platform was evacuation.
"A structural collapse can arise through considerable shifts and deformations ...The unit can then in the worst case drop down vertically, penetrate the tank and/or tip over on either side with a danger of damaging nearby pipelines/umbilicals," Talisman said.
"Without compensating measures there is great probability of cracks forming and a loss of carrying ability ... by the platform's legs before or during the coming winter season."
A Talisman spokesman in Norway declined to comment on Thursday.
Substructure problems forced the evacuation of the platform, which is owned by Dutch maritime oil and gas engineer SBM Offshore .
SBM Offshore could not be reached for comment on Thursday.
The oilfield where the platform sits has not been operated since 2001, so the risk of a spill is limited to 80 cubic metres of diesel, 200 litres of the toxic bleach hypochlorite, and small amounts of other chemicals, Talisman said.
The oil wells are not at risk, it said.
Talisman has been given a deadline of Dec. 31 by the Norwegian Petroleum Directorate (NPD) to deliver a new development plan for Yme which addresses its safety issues.
An NPD spokeswoman said it was up to Talisman to propose fixes, which the company in its letter said would be outlined by November.
It was also considering transporting the platform back onshore but this was not possible before 2013, after the winter storm season.
Yme was constructed in Abu Dhabi and refitted in Norway for use in the North Sea. However, safety authorities compiled a list of thousands of faults and refused to permit it to operate until repairs were made.
The Yme field was discovered in 1987 and has reserves of 12 million cubic metres of recoverable oil left. It would be the first field in Norway to be redeveloped after Statoil operated it from between 1996 to 2001.
Talisman has written off some of its Yme investment. In August it reported an end-June remaining book value associated with the investment of $644 million.
In addition to its 60 percent stake in the installation, Polish refiner Lotos has 20 percent, Norske ADEC holds 10 percent and Wintershall, an arm of BASF , has 10 percent.
(Additional reporting by Victoria Klesty, Balazs Koranyi and Terje Solsvik; editing by Jason Neely)
Keywords: NORWAY YME/