Hornbeck Offshore has exercised options to build four more offshore support vessels (OSVs) for $180m.

The four vessels, which include two 310 class and two 320 class OSVs, are part of 48 shipyard options and are scheduled to be delivered in the fourth quarter of 2014 and the first quarter of 2015.

Hornbeck’s order is part of its 64 vessel newbuilding programme launched in November 2011 and will expand the company’s fifth OSV newbuild programme from 16 vessels to 20 HOSMAX class DP-2 new generation OSVs for its upstream business segment.

The company said that the option period for the remaining 44 ships has been stretched by 60 days each without changing the pricing and original delivery dates.

As a result, Hornbeck’s decision on the exercise of the next option at each of the two shipyards is not due until 1 February 2013 and 19 February 2013, respectively.

Delivery dates for the remaining 44 vessels, if they are exercised, will be around 24 to 26 months following the date of each respective option exercise, with the last newbuild vessel under this programmme to be delivered in January 2018.

The 20 vessels are being built at two US-based shipyards, which qualifies the company for coastwise trade in the US Gulf of Mexico under the Jones Act.

Hornbeck expects the vessels will be capable of serving all three of the company’s core markets in the US Gulf of Mexico, Brazil and Mexico.

All the OSVs planned for construction will be equipped with Dynamic Positioning 2 (DP-2), with cargo-carrying capacities ranging between 5,650dwt and 6,200dwt.

The company is also planning to invest $50m to start a retrofit programme to upgrade six 200 class DP-1 OSVs into 240 class DP-2 OSVs.