The oiler said planning permission had been extended for a further 36 months at a meeting of the East Riding of Yorkshire Council's planning committee.
The firm formally completed an acquisition of a 16.667% stake in the West Newton gas discovery earlier this month as part of a deal with Rathlin Energy, a subsidiary of Canadian firm Connaught Oil & Gas.
The discovery is located onshore UK in East Yorkshire, within the western part of the Southern Zechstein Basin, and contains an estimated contingent resource of 189bn cubic feet of gas equivalent or 31.5mln barrels of oil equivalent.
The West Newton appraisal well is planned to be drilled in the first quarter of 2019, with planning permission for the conventional well already in place.
Union Jack shares were up 4.2% at 0.11p.