The well is expected to take between 20 and 30 days to drill, Irish junior and block partner Lansdowne Oil & Gas said.
Petronas hired the Diamond Offshore Drilling semisub in late June, although a deal value was not disclosed.
Petronas, through subsidiary PSE Kinsale, holds an 80% interest in SEL 4/07, with Lansdowne holding the remaining 20%.
Following a farm-in agreement signed in November last year, PSE Kinsale is due to fund 100% of the costs of drilling the well, as well as site survey works and costs of any testing programme up to $2.5 million.
The Irish junior first put the Midleton licence out for potential farm-out in 2011 on foot of new 3D seismic data also covering the neighbouring Amergin and Rosscarbery prospects.
The SEL 4/07 licence lies immediately south-east of Petronas’ Kinsale Head field, which is Ireland’s only producing gas project.
Midleton is estimated to hold potential for 330 billion cubic feet of gas initially in-place from the same Lower Cretaceous ‘A’ sands that are already producing at Kinsale Head.