 Tiber was initially drilled by <unk> 's fifth @-@ generation dynamic positioned semi @-@ <unk> oil rig , Deepwater Horizon , with <unk> drilling commencing around March 2009 , slightly delayed from the planned date of September 2008 . Much of the deeper gulf reserves are buried under salt <unk> thousands of feet thick , which present a problem for seismic exploration . BP had previously developed exploration techniques to bypass this difficulty . Oil was located at " multiple levels " . The field was announced on September 2 , 2009 , and BP shares rose 3 @.@ 7 percent on the news . With Tiber joining at least ten other successful Lower Tertiary <unk> in the area , analysts viewed the announcement as a sign for optimism , and a <unk> of renewed interest in , and production from , the offshore Gulf of Mexico . 
