The extensions were granted at a Lincolnshire County Council Planning Committee today and the permissions are now in place until December 2020, the company said in a statement.
"We are delighted with the Planning Committee's favourable decision to extend the planning permissions at Biscathorpe and North Kelsey,” said David Bramhill, Union Jack executive chairman.
"Biscathorpe-2 holds considerable upside potential for our Company with gross prospective oil resources of 14 million barrels and a high geological Chance of Success of 40%.
Bramhill added: “We are enthusiastic about commencing drilling operations expected around mid-year 2018 and look forward to updating the market on progress in due course."
UJO shares climbed 11% to change hands at 0.11p.