The partners on the project - Petrol's subsidiaries Geoenergo and Petrol Geoterm together with Ascent Resources from the UK - have been struggling for several years to obtain an environmental permit for a gas gathering and separation station.

The procedure has been bogged down by requests by environmentalists, which oppose fracking in the area for fear that it will pollute groundwater, which has led to the permit being successfully challenged several times.

The project partners, however, say that the method used would not be fracking but the much less dangerous hydraulic stimulation of slate.

"The unfounded hampering of the acquisition of the requisite permits has had explicitly negative consequences on the development of the project," Geoenergo told the STA.

In October, the partners therefore decided to ship gas to Croatia, via an existing pipeline from the town of Lendava to Croatia, where it will be purified by oil company Ina and sold in the EU.

The solution is provisional, in place until such time as the permits for the Slovenian plant are finalised, but Geoenergo says it is impossible to say how long that might take.

It also remains unclear how much gas can be extracted from the two wells that will be used in the initial stages. Original estimates put the potential of the gas field at about 12 billion m3 of gas, with Ascent originally projecting a daily output of 300,000 m3.

Geoenergo says that more precise figures would be available once pumping starts, when the recoverable quantity of gas for the field will be estimated as well.

The two wells drilled in Petišovci 2011, Pg-10 and Pg-11A, are now being prepared for production and short connecting pipelines have to be built to the existing network.