There was a time, not long ago, when an oil field was considered tapped out, even though it was well known that most of the oil down there was untouched. The Salt Creek Oil Field in Natrona County, Wyoming, is a massive historic petroleum deposit. The peak came in the 1920s as the area became the largest-producing oil field in the Rocky Mountains and briefly one of the largest globally. Salt Creek Oil Field in Natrona County utilizes advanced 3-D seismic imaging, non-surface-disturbing exploratory methods, and enhanced oil recovery (EOR) techniques like carbon dioxide (CO₂) injection rather than traditional heavy drilling. There are estimates that over 1 billion barrels of oil remain in the ground at the historic Salt Creek Oil Field in Natrona County, Wyoming.