It seems a fair summary of the situation but I've reservations about the tail of production stretching out as far as 2050 as per the above graph. At the Offshore Europe Exhibition and Conference held at Aberdeen in Sept'05 (which I attended) speakers referred to a relatively short 'window of opportunity' to develop remaining N Sea prospects.  This limitation is due to a combination of the design life of major NS infrastructure together with decreasing size of new discoveries.  Structures built in the 1970's such as Brent, Forties and Frigg pipelines will be at the end of their design life by around 2020 and would doubtless then require huge investments to offset the ever present problem of corrosion.

There are some major structures built later (such as CATS, c1990) but most of the key NS infrastructure will be retired by or soon after 2020 and subsequent new discoveries would need to be large (or several medium sized finds close together) to justify the effort necessary to bring the oil / gas ashore beyond this point.  I know the economists will point to prices being much higher by then to justify the investment but I suspect a lot of the problem will be down to energy economics whereby the energy required to build and maintain the infrastructure will approach the energy recovered from the (by then) small oil and gas deposits.

On this basis I would envisage a sharper and earlier production cutoff, and well before 2050.

Chris