An oil rig is seen lit up on the outskirts of Havana April 5, 2011. Repsol YPF expects to have a Chinese-built drilling rig in Cuban waters by the end of the summer and start drilling immediately into a prospective undersea oil field that looks like it could be a big one, a geologist for the Spanish oil company said on Monday. Picture taken April 5, 2011. REUTERS/Desmond Boylan (CUBA - Tags: POLITICS ENVIRONMENT ENERGY BUSINESS)