Production has begun in the Boulton H Well gas field in the southern North Sea, according to Tullow Oil plc.
Boulton H is the last field to be brought on production as part of the five field CMS III development programme.
It has been developed using the production and transportation facilities of the Caister Murdoch System (CMS), located 115 miles north east of the Lincolnshire coast in England.
Tullow has a 14.1% unitised equity in CMS III.
Aidan Heavey, Tullow’s CEO stated: "We congratulate ConocoPhillips on bringing the CMS III project to a successful conclusion.
"The CMS III project demonstrates the successful application of modern technology to existing discoveries and we look forward to further value-creating initiatives in the area, via both new drilling and third party business," he added.
Tullow is currently reappraising a number of discoveries using the latest seismic technology.
Shares in the company traded €1.55 on the ISEQ this morning.