Romania’s OMV Petrom and US oil giant ExxonMobil have started drilling at a third exploration well in the Neptun Block off the Romanian Black Sea coast, Petrom said on Monday.

“The Pelican South-1 well will test a new geological structure on the Neptun Block,” Romania’s biggest oil and gas group said in a statement.

The Ocean Endeavour rig completed drilling the Domino-2 well earlier this month and data from the well are being evaluated, it added.

ExxonMobil Exploration and Production Romania, a unit of the US oil major, and OMV Petrom each hold 50% of the deepwater sector of the Neptun Block. 

Two years ago, Petrom and ExxonMobil said they had discovered a gas deposit estimated at 42 to 84 billion cubic metres (bcm) of gas at Domino-1, the first deep water exploration well in Romanian waters.

Since then, the two companies have made additional explorations to evaluate the commercial viability of the gas accumulation at the Neptun Block.

"Exploration for oil and gas in frontier areas is complex and very detailed, often taking years to complete. A thorough understanding of the geology is essential prior to making the significant investments required to develop such a discovery", John Knapp, managing director of ExxonMobil’s subsidiary in Romania, said in the statement.