Exit by two foreign firms leaves Polish shale gas under cloud
* Marathon, Talisman say quitting Polish operations
* Polish government backs shale to replace Russian imports
* Critics say reality falls short of shale gas hype
* Estimates of reserves were drastically downgraded
* Energy executives complain about red tape
By Agnieszka Barteczko
WARSAW, May 8 (Reuters) - Canada's Talisman Energy and U.S. oil firm Marathon said they were quitting Polish shale gas operations, raising questions over the business sense of developing the deposits, once seen as a potential energy bonanza.
Poland's government, determined to find a new source of energy to replace the imported Russian gas on which it depends, has trumpeted its rock formations as the biggest potential source of shale gas in Europe.
The initial optimism among investors has been tempered by an unsettled regulatory landscape, and a downgrade of estimates for the size of potential reserves. Continued...