The upgrade comes as the project moves towards first gas production in 2020, following the award of a production concession last month. A year earlier, the Podere Maiar well was successfully drilled and tested at Selva.
United’s share amounts to 2.7bn cubic feet and it represents the company’s first reserves.
It comes a day after the confirmation that the drilling of Colter exploration, off England’s south coast, had kicked off.
Chief executive Brian Larkin described it as a “key milestone” for the company.
“Not only do these represent United's first reserves, they serve to demonstrate the considerable progress that has been made by the partners in de-risking the field and advancing it towards production,” Larkin said.
“With preliminary approval for the development plan received in January, we remain on course to bring Selva into production in 2020 with facilities designed to produce at a gross rate of up to 150,000 cubic metres per day.
“At this rate, Selva will be generating significant cash flows for United which in turn will be reinvested into further high-impact activity across our portfolio of late-stage development opportunities onshore Europe and frontier exploration offshore Jamaica.
“We are encouraged by the additional prospectivity in the licence, particularly by a number of potentially larger targets immediately adjacent to the Selva Gas Field, and this was one of the key drivers behind United's original acquisition of this licence.”