Union Jack Oil has confirmed that testing at its Sark well in central Oklahoma, United States, did not result in commercial hydrocarbon production, marking an unexpected setback in the company’s ongoing US exploration efforts.
Union Jack, which holds a 53 per cent interest in the Sark well, conducted a 30-day production test on the Prue Sandstone interval, where earlier evaluation had identified hydrocarbon-bearing potential.
However, the well failed to deliver commercially viable hydrocarbons during the test.
The Sark well was drilled to a total depth of 5,391 feet and underwent the installation of temporary surface production facilities ahead of the testing program.
Following post-test analysis, Union Jack said that while the well encountered a valid structural closure, the geological trap had subsequently been breached, limiting the potential for hydrocarbon recovery.
Union Jack executive chairman David Bramhill acknowledged the disappointing outcome, highlighting the company’s broader portfolio strength.
“Following the drilling of four successful discoveries in Oklahoma to date, this is an unexpected and disappointing result,” he said.
“Our US interests, with income from Moccasin, the Andrews Field and Mineral Royalties, continue to be profitable and we look forward to continuing our Oklahoma drilling programme.”
The Sark project was part of a broader US expansion strategy by Union Jack aimed at diversifying income streams and building on recent success across its American operations.
In July, the company announced a farm-in agreement with operator Reach Oil and Gas, through which it acquired a 60 per cent working interest in the Sark well.
The well target comprised a significant dip and fault-closed structure supported by 3D seismic data, spanning approximately 156 acres with a structural relief of 40 feet.
Internal estimates had suggested the feature could contain recoverable resources of around 1.44 million barrels of oil.
Union Jack previously projected that the total cost to drill, complete, and develop the Sark well would be approximately US$1.1 million (£842,035) net to the company, including back costs of $236,800.
At the time of acquisition, Union Jack estimated a 65 per cent probability of success for hydrocarbon discovery in the targeted Prue Sandstone structure, which encompasses multiple potential prospects.
Despite the setback, the company maintains a confident outlook on its US holdings, underpinned by production revenues from other Oklahoma assets.
While the Sark well did not yield the commercial results anticipated, Union Jack Oil views the experience as part of the inherent risk-reward balance of upstream exploration.
The company noted that data gathered from the project will contribute valuable insights to its geological understanding of the region, informing future drilling and investment decisions across its expanding US portfolio.
