The each drill rig is estimated to be worth $525m.

The contract follows a letter of intent signed in March for the rigs to be built at Cosco’s Nantong shipyard.

According to the payment terms 20% amount will be paid as the down payment, with the remaining 80% to be paid after the delivery of the rigs.

Delivery of the rigs is scheduled for the fourth quarter of 2013 and the second quarter of 2014, reports Reuters.