The company said it had signed a deal for 2,600-dwt ships at Wuxue Janda Shipbuilding.
The contract comes with options for two more vessels in the series.
The price per vessel is EUR 3.25m ($3.9m).
Wilson added the order is conditional on the yard providing a refund guarantee.
Delivery is set for 2016.
The owner operates a fleet of 111 vessels.
