As a child, Dave O'Reilly, Chevron's chief executive, was taught by his father, a general manager of a Dublin department store, to tackle the challenges life offers head-on. He was encouraged to work hard and take the tougher classes in high school, such as maths and sciences.

This early lesson pushed Mr O'Reilly up the ranks of Chevron, which he joined as a process engineer immediately after earning his degree in chemical engineering from University College, Dublin.

He has a reputation for being humble and affable – qualities that help in relationship-building with oil-rich countries. That is key to success in an industry increasingly dominated by national oil companies. It kept him in Venezuela when others left in the wake of the nationalisation of energy assets. And it has helped bring Chevron a longer queue of projects than anyone else. At the age of 62, Mr O'Reilly continues to travel extensively to keep track of his company's ventures.