"One positive side effect of the downturn that we have seen is that the majors have changed the way they approach exploration, leading to improved returns, even at lower prices," said Andrew Latham, WoodMac's vice president of exploration research.

"Exploration has a new role – less is more."

According to WoodMac, major operators invested some $169 billion in exploration from 2006 to 2015, adding a total of 72 billion barrels of oil equivalent to their resource base, about 25 billion boe of which came from unconventional plays.

However,