## 2 Oil Shale Properties
### Organic Matter Type in Oil Shale  
Oil shale comprises diverse organic components, such as kerogen, bitumen, and other hydrocarbons [20; 21; 22]. The composition and quantity of organic matter can differ based on the unique properties of each oil shale deposit. The kerogen-abundant portion can be employed to produce shale oil from the oil shale, while the kerogen-scarce portion can be used for generating power. Kerogen is a complex mixture of organic compounds derived from ancient marine, terrestrial, and lacustrine (lake) sediments. It primarily consists of carbon, hydrogen, oxygen, nitrogen, and smaller amounts of sulfur. The exact composition can vary depending on the source and maturity of the kerogen. Kerogen is formed from the remains of ancient plants and microorganisms that lived millions of years ago. Over time, these organic materials were buried and subjected to high pressure and temperature, leading to the transformation of the organic matter into kerogen. Type I kerogen has a high hydrogen-to-carbon ratio and excellent oil-generating potential, derived mostly from algae. Type II kerogen is derived mostly from terrestrial and marine plants and has moderate oil-generating potential. Type III kerogen is mostly derived from terrestrial plants and has relatively low oil-generating potential. [PERSON], in 1987 classified oil shale based on existing petroleum and coal science technologies. The classification is mainly based on algal minerals. Based on different compositions of the algal minerals, oil shale could be classified into cannel coal, torbanite, lamosite, marinite, tasmanite, and kuckersite. Based on different algae forms, oil shale can be classified into charophyte macareals and lamalginite, primarily derived from unique algae and limited algal minerals. [PERSON] et al. (2016) performed float and sink analyses on unprocessed oil shale samples from Longkou, China. They discovered that the predominant inorganic constituents were quartz, kaolinite, montmorillonite, calcite, analicme, dolomite, and pyrite. Additionally, they found that lower-density fractions contained a greater concentration of kerogen [23]. [PERSON] et al. (1995) classified the Green River oil shale based on different criteria. The shale can be classified into Mahogany Zone and Parachute Creek Zone based on origin content. The Mahogany Zone contains a higher amount of organic carbon, averaging around 30%. It is considered an oil-prone zone, as it has a higher potential for liquid oil production during thermal processing. On the other hand, the Parachute Creek Zone has a lower organic carbon content, averaging around 15%, making it a gas-prone zone. It predominantly yields natural gas upon thermal processing. Based on thermal maturity, which refers to the degree of organic matter transformation due to heat and pressure [24; 25; 26]. Green River oil shale can be classified into the following three thermal maturity levels: immature, mature, and over-mature. The maturity level affects the type and quantity of hydrocarbons that can be extracted from the shale. Immature shale has a higher potential for oil generation, while over-mature shale tends to produce more gas. In addition, the classification could also be based on the functional groups in the organic compounds present in oil shale, such as carboxylic acids and esters, nitrogen-containing compounds like amines and pyrroles, as well as sulfur-containing compounds such as thiophenes [27]. [PERSON] et al., analyzed oil shale samples from the Lajun area in Central Jordan. They applied comprehensive organic geochemical and petrological studies to determine the nature of these oil shales. The methods of classification and characterization involved the use of biomarkers, thermal maturity indicators, and microscopic observation of organic matter [28]. Based on the organic geochemical analysis, a series of methods, including analyzing total organic carbon (TOC), total sulfur content (T.S. ), and potential yield (P.Y.) values, were applied.