Russia has sufficient recoverable oil reserves to last for 28 years, Minister for Natural Resources and Environment Sergei Donskoi said in a March 17 interview with the official government daily Rossiiskaya Gazeta.

Potentially recoverable oil reserves amount to about 29bn tonnes, according to the minister. To compare, Russia's crude oil production in 2015 amounted to about 505mn tonnes. While at face value the reserves are sufficient for 57 years, only 14bn tonnes is extractable at current prices, Donskoi said.

As Russia recalibrates its development strategies amid a slump in oil prices, the long-term potential of hydrocarbon extraction is also being revised.

The Ministry of Energy this year drafted a long-term oil sector strategy with four development scenarios, none of which assumes oil output growth, but forecasting 1.2% extraction decline through 2035 at best and a 46% drop in the worst-case scenario, Vedomosti daily reported on March 9.

Potential regulatory changes pose a greater risk to the ratings of Russian oil companies than low oil prices, Standard & Poor's warned in mid-February.

Proposals under discussion include possibile lowering of extraction tax exemptions that oil firms currently enjoy, or increasing excise duties on oil products.

"In our view, rating pressure could increase, depending on the extent to which the Russian government may make changes to current oil industry regulation," said S&P credit analyst Alexander Griaznov.

The agency's base-case scenario remains that the Russian government will "try to find a reasonable balance between its fiscal interests and the long-term success of the oil sector, which will remain key to the economy in the foreseeable future", Griaznov added.