Poland’s estimated recoverable reserves of so-called tight gas are probably higher than its proven conventional deposits of the fuel, according to the Polish Geological Institute.

The nation may be able to recover about 10 percent of estimated tight gas reserves of as much as 2 trillion cubic meters (70 trillion cubic feet), the institute said Tuesday in Warsaw. That compares with conventional proven reserves of 134 billion cubic meters of the fuel, or about eight years of annual consumption.

Exploration of tight gas, which is trapped in impermeable rocks and requires techniques including hydraulic fracturing to extract, may revive the nation’s hopes to boost gas output and cut dependence on Russian fuel. Recoverable shale reserves estimated at as much as 768 billion cubic meters by the PGI have failed to lead to increased production, leading foreign investors from Chevron Corp. to Exxon Mobil Corp. to abandon shale gas projects in the nation.

While production of tight gas is technically easier than breaking into shale deposits, layers can be as deep as 6,000 meters (20,000 feet), potentially hurting the viability of drilling, Hubert Kiersnowski, a co-author of the PGI report, said at a news briefing.

“These estimates are good news for investors,” Marcin Zieba, general director at the Polish Exploration and Production Industry Organization, told Bloomberg News. “Depth like any problem can be overcome.”