Commenting on a decline of 173 billion cubic feet from the previous year, Chief Executive Officer Brian Bjordal said natural gas exports depend on a wide array of variables, such as market demand and transport capacity.
"This interaction creates natural variations, and the reduction in last year's deliveries accordingly does not represent a trend," he said in a statement.
"Norwegian gas exports in any event represent a substantial contribution to energy supplies in major European countries, and remain stable at a high level."
The state-owned company reported 3.6 trillion cubic feet of natural gas was sent from the shelf to terminals in Belgium, France, Germany and the United Kingdom in 2013 -- a decline of 173 billion cubic feet from 2012.
Gassco said the transport system for Norwegian gas last year was reliable 99.68 percent of the time, compared with 99.69 percent for 2012.
Norway is the second-largest natural gas exporter in the world after Russia and ranks fourth in natural gas production.