Growth in North Sea oil?

It is easy to think that oil exploration and production is winding down in the North Sea, since it began in the 1960s and production was supposed to have peaked in 1999.  But this article on the BBC website demonstrates that there are still new oil fields to be exploited.  The Mariner oil field will not start producing oil until 2017 and is predicted to go on doing so until 2047.  And this is only one example of fields that remain to be exploited on the Continental shelf.  In 2011 and 2012, there has been the highest level of investment in oil field development ever.