Canadian energy company Nexen has signed an amended agreement with Ensco regarding the ENSCO 8502 ultra-deepwater semi-submersible drilling rig.

Under the amended agreement, Nexen is entitled to a special rate until such time as the rig is mobilized to the first drilling location designated by Nexen.

Nexen president and CEO Marvin Romanow said that Nexen has submitted applications for permits to drill its near-term exploration prospects and is waiting on approvals.

"As we await these approvals, our estimated cost for non-productive time ranges from $15m to less than $40m assuming we are able to commence drilling later this year or at the beginning of the second quarter 2011. We are actively pursuing opportunities to further reduce this cost." Romanow said.