Exploration for offshore oil & gas began in Ireland during the early 1970’s. The Kinsale Head Gas Field was discovered in 1971 by the US Company Marathon Oil Corporation. The field which is 50 kilometres off the coast of Co. Cork, in 90 metres water depth and is still the largest single hydrocarbon discovery made in Ireland, and PSE Kinsale Energy Limited remained Ireland’s only indigenous source of natural gas until 2015.

The Kinsale Head natural gas reservoir is located in reservoirs some 2,750 feet (840 metres) below sea level in the Celtic Sea, with the gas being produced to surface through two fixed steel production platforms, Alpha and Bravo, which were installed in 1977. Production began in 1978, initially supplying gas to the power station at Aghada and subsequently to the entire country.

Peak production occurred in 1995 at 99 bcf per year. The field had been in decline in recent years and Cessation of Production occurred in July 2020 and the company is now engaged in decommissioning the facilities safely, efficiently and with due regard to the environment, in accordance with all applicable laws and regulatory requirements.

A number of satellite gas fields were discovered and tied back to the platforms through 1990-2003, including:

• Ballycotton in 1991
• Southwest Kinsale in 1999
• Seven Heads in 2003 (developed by Ramco Energy)

Gas from satellite fields such as Ballycotton was produced using subsea well technology, whereby the wellheads are on the sea-floor and controlled remotely from one of the main production platforms. These satellite fields are very long distances from the platforms, such as Seven Heads, which is 35km southwest of Kinsale Head

Gas from all of the offshore fields was combined, compressed and piped from the Alpha platform to Inch Terminal near Midleton, Co. Cork. From Inch Terminal, the gas was then metered and transferred to Gas Networks Ireland (GNI) for distribution nationwide.

The Southwest Kinsale Field was redeveloped as Ireland’s first offshore gas storage facility and operated from 2001 to 2017.

The company was acquired by PETRONAS from Marathon Oil Company in 2009. PETRONAS is a major Fortune 500 oil and gas company, with extensive world-wide gas and LNG operations.

All the gas production wells are in the process of being decommissioned.