Brokers said the 6,500-hp AHTS units will be built at Shanghai Zhenhua Heavy Industries (ZPMC).
The 1,700-dwt ships will be delivered between June and November 2016. No price was revealed.
Earlier this month the CNOOC company signed up for a quartet of 2,500-gt, 8,000-hp anchor-handlers at Guangxin Shipbuilding & Heavy Industry.
It already had 12 anchor-handlers on order at various Chinese shipyards.
