Rising oil prices have renewed interest in developing domestic sources of oil.
Rising crude oil prices and concerns about the stability of some oil producing nations have increased interest in developing domestic energy sources in the United States. Many people are surprised to learn the largest deposits of oil on earth are found in the oil shale of the United States. Estimated worldwide reserves of conventional crude oil are 1.3 trillion barrels. Experts estimate the oil shale of the United States holds over 2 trillion barrels of recoverable oil.
Oil Shale Explained
Oil shale is a fine-grained sedimentary rock that is rich in organic material called “kerogen,” from which liquid hydrocarbons are produced. In geologic terms, oil shale is younger than crude oil deposits. The natural forces of heat and pressure have not yet converted the oil shale into crude oil.
Because the kerogen is trapped within the rock, oil shale must be mined and requires more processing than crude oil. It cannot be substituted directly for crude oil in all applications, but it can be converted into high-quality jet fuel, diesel fuel for power plants and other useful byproducts.
Oil Reserves vs. Resources
Oil shale “resources” represent the estimated total barrels of oil contained in oil shale deposits. There could be more than 6 trillion barrels of oil contained in America’s oil shale, but much of that oil is not recoverable.
Oil shale “reserves” represent the estimated quantity of oil that can be recovered economically using current technology. Estimates of current U.S. oil shale reserves are in excess of 2 trillion barrels.
The Green River Formation
The Green River Formation in the western United States contains the richest oil shale deposits on Earth. Covering parts of Utah, Colorado, and Wyoming, the Green River Formation holds an estimated 1.5 to 1.8 trillion barrels of oil shale reserves.
The Piceance Basin in Colorado holds perhaps 80 percent (more than 1 trillion barrels) of the in-place oil shale reserves in the Green River Formation. Oil shale in the Unita Basin in Utah holds perhaps 200 to 240 billion barrels of oil reserves, while the Green River Basin in Wyoming holds an additional 250 to 300 billion barrels.
Some smaller oil shale deposits within the Green River Formation have yet to be fully investigated.
The Devonian Oil Shale Deposits
The Devonian oil shale deposits extend through several eastern states, but over 90 percent of the minable oil shale deposits are in Kentucky, Tennessee, Ohio and Indiana. The black Devonian shale has been exploited as a source of natural gas for many years, but long been considered as a potential source of lower-grade shale oil.
The Devonian oil shale yields only about half of the organic matter (kerogan) as the Green River Formation oil shale deposits. Estimated total shale oil resources for the Devonian deposits are 420 million barrels.