Shell Oil's second and last drill ship, the Noble Discoverer, is on its way to the Chukchi Sea.

The company's spokesperson says the Noble Discoverer left Dutch Harbor Saturday. The oil giant said its confident the Arctic Challenger containment barge will be completed by the end of the month.

The certification of that barge is expected to trigger the final permits shell needs to drill.

The Discoverer is among a Shell fleet heading north for planned exploratory offshore drilling.