The quantities of oil at Katakolo, western Peloponnese, are four times larger than initially estimated, Energean sources revealed on Thursday.
Proven reserves amount to 10.7 million barrels, instead of the estimated three million barrels expected during the period of the tender.
Energean, which has assumed the management of the reserves, is planning to begin drilling in 2019.
Meanwhile, the environment and energy ministry approved the plan for the development of the field in August, while the environmental study has already been submitted for approval.
In Greece, the company also operates in Prinos; where proven reserves are 40 million barrels plus a 20 million additional potential, as well as in the areas of Ioannina and Aetolia-Acarnania (Aitoloakarnania), where the exploratory drilling has already started.
The Spanish company Repsol; which has a 60 pct share in the exploratory drilling, has launched a seismic study in Ioannina, while a contract for Aetolia-Acarnania is expected to be ratified by Parliament, after which the 60 pct transfer agreement and Repsol’s role as operator, will be activated.