The U.S. Energy Information Administration (EIA) has estimated that the unproven technically recoverable shale gas resources in Bulgaria amount to 17 trillion cubic feet.
The unproven technically recoverable shale oil in Bulgaria amount to 200 billion, the administration said in a recent report.
The estimated proved oil reserves in the country stand at 15 million barrels.
Technically recoverable resources are the volumes of oil and natural gas that could be produced using current technology, regardless of the production costs and the oil and natural gas prices.
In Bulgaria, shale gas explorations and extraction using hydraulic fracturing, or fracking, were banned indefinitely in early 2012. The government then withdrew the five gas exploration licences previously granted to Chevron Bulgaria Exploration and Production.