When an angry Enrico Mattei coined the phrase "the seven sisters" to describe the Anglo-Saxon companies that controlled the Middle East's oil after the second world war, the founder of Italy's modern energy industry could not have imagined the profound shift in power that would occur barely half a century later.

As oil prices have trebled over the past four years, a new group of oil and gas companies has risen to prominence. They have consolidated their power as aggressive resource holders and seekers and pushed the world's biggest listed energy groups, which emerged out of the original seven sisters - ExxonMobil and Chevron of the US and Europe's BP and Royal Dutch Shell - on to the sidelines and into an existential crisis.