The licence will now be valid until 20 December 2019 following the extension.
IOG is currently planning to drill a new well on the Harvey structure by 20 September 2019, while the rig contract is expected to be awarded by 20 November next year.
The Harvey structure has gross best case unrisked prospective gas resources of 114BCF.
Independent Oil and Gas CEO and interim chairman Mark Routh said: “We are pleased to have received a two-year extension to the Harvey licence, as it further validates our commitment to drill the well on what has the potential to become our largest gas asset.
“We will now progress to finalise our plans to drill the well and look forward to providing details in due course.”
Harvey is located directly between IOG’s BLYTHE and Vulcan Satellites hubs.
Gas from the Harvey facility is expected to be exported via the Thames pipeline upon the completion of appraisal works.
The company noted that the development of Harvey could have significant economic synergies with its two gas hubs.
IOG revealed earlier this month that the expected monetary value (EMV) for the Harvey licence is around £79m.
The overall Harvey structure is said to have a gross unrisked post-tax net present value (NPV) of £159m at 10% discount, while the licence is estimated to have an NPV of £126m.