Norway is Europe's largest oil producer, the world's third-largest natural gas exporter, and an important supplier of both oil and natural gas to other European countries.
Norway is the largest oil producer and exporter in Western Europe.
Norway is the world's third-largest exporter of natural gas after Russia and Qatar, and, as of 2012, Norway was the sixth-largest dry natural gas producer.
(from http://www.eia.gov/countries/country-data.cfm?fips=no)
Its oil production counters Russian leverage on Europe. Its borders peak into the top of Russia and its coastline provides observation of the Barents Sea and the Norwegian Sea.
In any conflict involving Russia (currently the only nuclear equipped nation invading/annexing its neighbours) it will be very strategic.