ERC Equipoise, IOG’s consultant, has also estimated an unrisked gross valuation of £159mln for the overall Harvey structure, and £129mln for the licence.
IOG is committed to drilling a well at the Harvey project within two years, and well scheduling is currently underway.
"We are delighted with the result of the CPR and the EMV of the Harvey structure on our licence being determined at £79mln,” said chief executive Mark Routh.
“This clearly validates our commitment to drill the well on what has the potential to become our largest gas asset.”
Routh added: “The value of Harvey is strengthened by the synergies with our Southern North Sea gas development hubs, notably shared use of a fully owned Thames Pipeline gas export route.
“Alongside these two hubs, the Harvey appraisal opportunity therefore represents very material upside to IOG even on the mid case volumes. We are therefore actively considering how soon we can drill the well. We look forward to updating all stakeholders in due course."