The Statfjord north flank development in the North Sea was brought on stream by Statoil in the afternoon of 26 August.
Oil is flowing initially from two wells, reports project manager Kåre Søvik. Another oil producer and a water injection well are planned for next year.
"We're very satisfied with the start-up, and with the fact that we achieved it during August," says Mr Søvik.
The project has been implemented in roughly 22 months, despite a serious accident to a pipelaying vessel at a very critical phase in the work.
This damage means that the start to production is three weeks behind the original schedule.
The Statfjord north flank, which forms the northernmost extension of the field, has been brought on stream within the framework of the Statfjord development projects (SFU) organisation.
It is developed as a satellite with two subsea templates - one for oil production and the other for water injection. Wellstreams are transferred to Statfjord C for processing, storage and offshore loading.
Based on data from the first production well, recoverable reserves in the north flank are put at 75 million barrels - half the initial estimate.
But platform manager Arild Pettersen on Statfjord C emphasises that Statoil is now able to recover oil from the northernmost end of the field, which has been difficult to get at earlier.
An output of roughly 25,000 barrels of oil per day, combined with other satellite production, will help to extend the producing life of Statfjord C to about 2012-2014.