The consortium announced this week it was entering "an intensive period" as it prepares the control system for the integration of the twin pipelines into a single network. Completion of the second line was expected by June.
"We are very pleased to have completed pipelay for Line 2 well in advance of the planned schedule," Ruurd Hoekstra, deputy project director for construction, said in a statement. "It is another major milestone for Nord Stream."
The three sections that make up the second offshore leg are set for pressure testing and connection this summer. They'll be commissioned this year as part of an automated twin pipeline system.
The lines, once fully operational, will transport around 1.9 trillion cubic feet of Russian gas each year to European consumers for at least 50 years.
Nord Stream is part of a network of pipelines planned to add diversity to Russia's natural gas exports to European consumers.