* Shale reserves boost global reserves by 11 percent * Russia tops list of oil shale holders * Algeria shale gas resource estimate jumps threefold By Edward McAllister and Timothy Gardner NEW YORK/WASHINGTON June 10 Estimated global reserves of oil in shale rock deposits will boost total world crude resources by 11 percent, a U.S. government report said on Monday, offering a preliminary glimpse of the hydrocarbons that remain untapped across the world. In the first study of its kind by the U.S. government, the Energy Information Administration estimated technically recoverable shale oil reserves in 41 countries at 345 billion barrels. Previous EIA reports only included U.S. shale oil resources, which in 2011 were estimated at 32 billion barrels. It now estimates U.S. shale oil reserves at 58 billion barrels. Meanwhile, global shale gas reserves have risen to 7,299 trillion cubic feet, up from 6,622 tcf estimated in 2011, said the EIA, the independent statistics arm of the Department of Energy. Technically recoverable reserves are an estimation of the amount of oil or gas that can be extracted with today's technology. Russia topped the list of oil reserves, with 75 billion barrels, ahead of the United States with 48 billion, China with 32 billion and Argentina with 27 billion barrels, according to an assessment prepared for the EIA by Advanced Resources International (ARI). ARI's estimate of U.S. technically recoverable shale oil resources was 48 billion barrels, 10 billion less than the EIA's estimate. The United States, with 1,161 tcf, held the highest natural gas reserves, according to ARI, ahead of China with 1,115, Argentina with 802 tcf and Algeria with 707 tcf. Algeria's estimate has more than tripled from the 231 tcf estimated in 2011. Oil and natural gas production has rocketed in the United States in recent years due to the emergence of horizontal drilling and hydraulic fracturing, or fracking, that have unlocked decades of supply from shale deposits dotted across the country. But while the EIA report offers a comprehensive glimpse of global shale potential, technically recoverable reserves are not a guarantee of supply and it is unclear if deposits outside the United States, with varying geology, can be developed economically. Even inside the United States some areas have proved to be more difficult and expensive to develop than others, halting development. "The reserves are one thing, but the ability to scale up the production for those reserves is another thing, which is not as straightforward in many parts of the world as it has proved to be in the U.S.," said Jan Stuart, head of energy research at Credit Suisse in New York. A clear example is Poland, ranked twelfth in the list of shale gas reserves, which has attracted a lot of interest in its shale potential over the past few years. Early drilling suggested extraction would be difficult and companies including Exxon Mobil, Talisman Energy and Marathon have since quit shale drilling there. Still, David Pumphrey, a senior fellow at the Center for Strategic and International Studies, said the report could help push countries like Argentina and Poland to develop their reserves. "The fact that it is there in the ground keeps reinforcing this is a big story," he said. Pumphrey expected further evolution in drilling technologies could make more and more of the resources economically favorable to produce in the future.