US oil reserves by state vary greatly with most of the attention for future oil exploration being placed on untapped shale oil reserves in Colorado, Utah, and Wyoming. US oil reserves by state are categorized into two different classifications: proven reserves and prospective reserves. Proven untapped oil reserves like those that reside in Alaska are estimated to be in the 134 billion barrel range. Prospective oil reserves such as those in Colorado, Utah, and Wyoming are thought to contain up to 1 trillion barrels of oil shale. As of yet there is no way to make usable oil from oil shale reserves. Studies done by the United States Government and private companies have shown great promise in finding a way to make usable oil out of oil shale. Oil shale is not actually oil but it is a waxy oil precursor known as kerogen.

New drilling techniques are also expected to play a big part in future oil exploration. Untapped oil reserves may be able to be accessed by new horizontal drilling technology. This new technology may enable drillers to be able to access hundreds of thousands of miles of untapped oil reserves.

US oil reserves by state are closely monitored and studied to see if new oil reserves or oil shale reserves are present. The Bureau of Land Management and United States Department of Energy are the primary agencies that oversee the research and monitoring. Future oil exploration looks bright as untapped oil reserves seem on the verge of being accessible.