Bulgaria's parliament eased a ban on hydraulic fracturing on Thursday to make it easier to allow exploration for conventional natural gas.
In January, the country banned exploration for shale oil and gas using fracking after widespread protests against the practice, which involves injecting water mixed with sand and chemicals into rock formations at high pressure.
But experts say because the ban also set a specific pressure limit on drilling, it also effectively prevented exploration for conventional deposits that are over 200 m deep and blocked work dozens of concessions.
Initial estimates showed Bulgaria may have significant shale gas reserves, up to 1.0 trillion cubic metres, which could help it cut its almost total dependence on Russian supply. But critics worry it may poison underground waters, trigger earthquakes and pose serious hazards to public health.
Economy and Energy Minister Delyan Dobrev said the easing of the ban was only meant to allow companies to explore for gas by conventional methods to boost local production and decrease Bulgaria's almost total dependence on Russian supplies.
"The change will by no way allow hydraulic fracturing for shale gas," national radio quoted Dobrev as saying.
Bulgaria plans to grant a concession contract to a TransAtantic Petroleum unit to start production of gas in northern Bulgaria, where it has discovered between three to six billion cubic metres of natural gas.
It is also awaiting bids by 1 July to explore a deepwater gas field off Black Sea coast, close to a field in Romanian waters where a successful discovery was made.