Subsea 7 is understood to have lined up a tender for the construction of two large flexible-lay ­vessels with 600-tonne and 1000-tonne tensioner capacities, respectively.

The leading offshore installation player is said to have shortlisted about half a dozen yards for the newbuild contract while it works on finalising the purchase of pipelay equipment from Dutch supplier Huisman.

The vessels are expected to be equipped with DP2 and will be built to the design proposed by the selected yard, sources said.

Dutch