U.S. EIA - Collectively, these companies added a net 8.2 billion barrels of oil equivalent (BOE) to their proved reserves during 2017, which totaled 277 billion BOE at the end of the year. Exploration and development (E&D) spending in 2017 increased 11% from 2016 levels, but remained 47% lower than 2013 levels.

Saudi Arabia effectively grew its recoverable oil resources by 73 billion barrels this year after lower tax rates for state producer Saudi Aramco boosted the country's estimated prospective resources.