The company said, in a statement, that the well was spudded today at 12:30pm.
It highlighted that the company’s economic modelling of Biscathorpe shows a £24mln pre-drill valuation net to Union Jack in the success case.
"Biscathorpe is one of the UK's largest onshore unappraised conventional oil prospects with Mean Prospective Resources of 14 million barrels gross and a geological chance of success of 40%, in which Union Jack has a meaningful 22% licence interest,” said David Bramhill, Union Jack executive chairman.
He added: "Biscathorpe is one of Union Jack's near-term, high-impact projects and success here will be transformational for our company.
“In addition to the defined structural closure, stratigraphic trapping, if present, could lead to significant upside for oil resources.
“We look forward to updating shareholders and the market with preliminary results from the well in early February 2019."