UK Oil & Gas (LON:UKOG) has confirmed flow testing is underway at the Horse Hill-1 well near Gatwick in Surrey.
The explorer created a furore in April last year when it said the well, drilled into the Weald Basin under Dorset, Surrey and Sussex, had discovered more than a hundred billion barrels of oil.
The extended flow test is designed to test both the oil bearing Upper Portland sandstone reservoir and two Kimmeridge limestone reservoirs beneath the Portland.
Testing operations are anticipated to take about 30 days to perform. The company will report the results of the tests once analysed.
Neil Ritson, Solo's chairman, said: "Collecting flow rate and reservoir engineering data is a key step in establishing commerciality and designing a development programme.
“We therefore look forward with great interest to reviewing the data with the Horse Hill partners as those results become available."
Solo owns a 6.5% interest in HH-1, located on the northern side of the Weald Basin near Gatwick Airport.
The well identified oil bearing reservoirs in a number of intervals including the Portland Sandstone and the Kimmeridgian Limestones.
It was the potential of the deeper Kimmeridge formations, referred to as ‘tight’ or contained in rocks, that was the basis of the eye-raising estimates.
Flow testing will establish how much of this potential can be commercially recovered.
Testing operations are anticipated to take about 30 days to perform and UKOG said it will report the results of the tests once analysed.