The Arctic has been the focus of oil and gas exploration since the 1960s. However, aside from this long history, specifically in areas such as Alaska, Norway, and Russia, Arctic exploration is still a slow and costly venture. Consequently, the region remains one of the world's last petroleum E&P frontiers. Recently, the USGS estimated that 25% of the Earth's remaining petroleum reserves (13% of the world's undiscovered oil and 30% of its gas) are contained in 17 known Arctic basins, some of which have had little or no exploration. These estimates vary because of the paucity of geologic and geophysical data, but the size of the prize remains consistently large.