This is what has the Arabs and Higher Cost Producers nervous.
According to Reuters this is what has happened from 2013 to 2016:
Cost per barrel from shale basins in the US:
Baaken , North Dakota –From $65/$66 to $30
Eagle Ford, Texas–From $83 to $39
Norbrara, Coladrao and Wyoming –From $76 to $37
Permian Delaware, Texas–From $81 to $39
Permian Midland, Texas–From $98 to $39