PetroHungaria owns the Penészlek field, which produces gas from two wells.
The AIM quoted firm says the deal is a way to realise the full value of the remaining production in an up-front cash payment. It plans to reinvest the cash into its Slovenian project.
"Given the relatively short life expectancy of the field and Ascent's limited cash position, it was deemed prudent to accept a proposal from our partners to dispose of our interest for this up-front payment, which gives us more certainty in terms of cash flow and cost control," said chief executive Len Reece.
Last year, Ascent had losses attributable to Penészlek of €40,000 and at the end of June the net assets were valued at €1.67mln.