What is Enriched Oil Shale?
Oil shale is literally called the "burning rock" (reachinformation.com). The reason behind this is because this layer of shale contains Kerogen; a solid mixture of the organic materials carbon, hydrogen, oxygen, nitrogen and sulfur (britannica.com). As it sounds, enriched oil is Kerogen that has high dissolved amounts of the element Carbon. The way carbon is absorbed into the oil shale is called "flooding"; this is a process where carbon dioxide (CO2) is pressed into the oil-bearing rock, under huge amounts of pressure, and helps to make the oil inside have a lesser viscosity. Western Colorado has one of the largest deposits, and richest, form of oil shale in the world; to a point the general area has become a research area for extraction projects. This is also due to the mahogany zone being about 2,400 feet below the surface of the Green River Formation; allowing for surface or deep mining operations of this sedimentary rock.
Extraction and Processing
Processing oil shale can be done either on-site (situ) or off site (ex situ); there is no preferred method. Oil shale can be mined as if it was coal: cut and crushed before being transported to the surface for processing (ex situ) or the sedimentary layers are heated underground and the oil is forced to flow to an oil pump (situ) (instituteforenergyresearch.org). Using one method or the other depends on how far down the oil shale layers are located. Hydraulic Fracturing of this shale layer allows for pieces of this layer to be pumped to the surface for oil extraction.
On its own, oil shale can be burned, at high temperatures, as a low-grade form of power fuel for districts or used for constructing materials as a chemical compound. Still, oil shale can be used to make shale oil. There is a big difference from these two types of shale, but generally, oil shale is the parent product of shale oil (CGS Rock Talk, pp. 1). The process starts by heating a mound of oil shale to 842 °F in a furnace; absent of any oxygen.The term for this heating process is called Retorting during the heating, Kerogen compounds decompose and separate into hydrocarbon (shale) oil and oil shale gas (http://science.howstuffworks.com).
Further explanation on oil extraction can be found here.
On its own, oil shale can be burned, at high temperatures, as a low-grade form of power fuel for districts or used for constructing materials as a chemical compound. Still, oil shale can be used to make shale oil. There is a big difference from these two types of shale, but generally, oil shale is the parent product of shale oil (CGS Rock Talk, pp. 1). The process starts by heating a mound of oil shale to 842 °F in a furnace; absent of any oxygen.The term for this heating process is called Retorting during the heating, Kerogen compounds decompose and separate into hydrocarbon (shale) oil and oil shale gas (http://science.howstuffworks.com).
Further explanation on oil extraction can be found here.
Why is the Oil Shale Enriched?
The oil shale in the Colorado Plateau underwent a similar form of CO2 flooding as time went on. Because the majority of the rock layers in the Colorado Plateau is sandstone, on theory, Natural Gas eventually leaked through the layers due to sandstone being porous and fine-grained. The reason behind this phenomenon was due to Colorado Plateau undergoing several seismic activities that eventually folded, cracked, and reduced much of the rock strata; in turn, released much of the Natural Gas that was already embedded in the shales. The Oil Shales eventually absorbed the carbon emissions and caused much of the sedimentary oil shale to become thick.