FocusGuyana basin could hold another 10 billion barrels says ExxonMobil exploration chiefExciting times are not a thing of the past for some exploration teamsDouble that: ExxonMobil exploration head Mike Cousins, watched by Tiago Homen of Petrobras and Liz Schwarze of ChevronPhoto: Todd Buchanan/CorporateEventImages/UpstreamGareth ChetwyndHouston