Modeling the transformation of І and ІІІ types kerogen by the method of entropy maximization

Keywords: organic matter, I and III type kerogen, equilibrium thermodynamics, Jane’s formalism, gas-generating potential, oil and gas potential, Ukraine oil and gas regions


Purpose, methods and research methodology. The aim of the work is to calculate and compare the trends of transformation of organic matter of I-A and III-A type kerogen, which is in contact with organic and inorganic gases in the process of immersion of organ-containing rocks. The calculations were performed for I and III type kerogen and a mixture of organic and inorganic gases within depths of 1-20 km and heat flows from 40 to 100 mW / m2.

Results, scientific novelty and practical significance of research. A comparison and analysis of changes in the total entropy of the system was performed for I and III type kerogen, which showed the complex nature of the total entropy functional dependence on depth. It was revealed that the entropy has two reversible sections, the maxima of which are at a depth of 6 and 12 km.

The analysis of changes in the Gibbs energy during the immersion of the geochemical system unambiguously indicates the presence of a stability zone for the hydrocarbon component. The maximum of this zone corresponds to the minimum value of the Gibbs energy, depends on the kerogen type and heat flow, is in the range of 4-7 km and indicates the area of stability, or "oil window".

The complex nature of the balance between constitutional water and kerogen, depending on the heat flow and depth, has been established. To analyze this equilibrium, a simple dehydration equilibrium constant (Kd) was proposed, which generalizes the transformations of water in the kerogen matrix. Thermodynamic methods were used to calculate and compare the gas-generating capacity of I and III type kerogen for all heat flows, which showed that I type kerogen is the most productive with gas-generating potential, and III type is the least productive.

To estimate the proportional composition of hydrocarbon gases in equilibrium with kerogen, the fat content coefficient of the gas generated by I and III type kerogen was calculated. It is shown that with immersion, the fat content coefficient first increases rapidly, which indicates an increase in the proportional content of alkanes heavier than methane. This growth reaches a maximum within 2-3 km for all considered heat flows, after which the fat content coefficient decreases.

The equilibrium constant of the Kolbe-Schmitt reaction is calculated, which showed that regardless of the heat flow, the rate of kerosene decarboxylation decreases with increasing depth due to the shift of equilibrium to the left, and the contribution of this reaction to kerogen conversion is insignificant.


Download data is not yet available.

Author Biographies

Олександр Любчак, Institute of Geology and Geochemistry of Combustible Minerals of NAS of Ukraine

PhD (Geology), Senior Researcher

Мирослав Павлюк, Institute of Geology and Geochemistry of Combustible Minerals of NAS of Ukraine

Academician of the National Academy of Science of Ukraine, DSc (Geology and Mineralogy), Professor, Director

Юрій Хоха, Institute of Geology and Geochemistry of Combustible Minerals of NAS of Ukraine

PhD (Geology), Senior Researcher, Senior Research Officer

Мирослава Яковенко, Institute of Geology and Geochemistry of Combustible Minerals of NAS of Ukraine

PhD (Geology), Senior Researcher, Scientific Secretary


Tissot, B.P., & Welte, D. H. (1984). Petroleum Formation and Occurrence. Berlin, Heidelberg, New York, Tokyo: Springer-Verlag.

Vandenbroucke, M., & Largeau, C. (2007). Kerogen origin, evolution and structure. Organic Geochemistry, 38 (5), 719–833.

Yamamoto, S., & Ishiwatari, R. (1989). A study of the formation mechanism of sedimentary humic substances—II. Protein-based melanoidin model. Organic Geochemistry, 14(5), 479-489.

Larter, S. R., & Douglas, A. G. (1980). Melanoidins – kerogen precursors and geochemical lipid sinks: a study us-ing pyrolysis gas chromatography (PGC). Geochimica et Cosmochimica Acta, 44 (12), 2087-2095.

Harvey, G.R., Boran, D.A., Chesal, L.A., & Tokar, J. M. (1983). The structure of marine fulvic and humic acids. Marine Chemistry, 12 (2–3), 119–132.

Schnitzer, M. (1978). Humic substances: chemistry and reactions. In Developments in soil science (Vol. 8, pp. 1-64). Elsevier.

Stevenson, F. J., & Butler, J. H. A. (1969). Chemistry of humic acids and related pigments. In Organic geochemistry (pp. 534-557). Springer, Berlin, Heidelberg.

Chekalyuk, E. B. (1971). Thermodynamic principles of the theory of oils mineral origin [Termodinamicheskiye os-novy teorii mineralnogo proiskhozhdeniya nefti]. Kiev, Naukova dumka, 256.

Khokha, Yu. V. (2014) Thermodynamics of abyssal hydrocarbons in the forecast of oil and gas deposits [Termody-namika hlybynnykh vuhlevodniv u prohnozuvanni rehiona-lnoi naftohazonosnosti]. Kyiv: Naukova dumka, 57.

Jaynes, E. T. (1957). Information theory and statistical mechanics. Physical review, 106(4), 620.

Ungerer, P., Collell, J., & Yiannourakou, M. (2015). Molecular modeling of the volumetric and thermodynamic properties of kerogen: Influence of organic type and maturity. Energy & Fuels, 29 (1), 91-105.

Fester, J.I., & Robinson, W.E. (1966). Oxygen functional groups in Green River oil-shale kerogen and trona acids. In: Gould, R.F. (Ed.), Coal Science (pp. 22–31). American Chemical Society, Washington, DC.

Vandenbroucke, M. (2003). Kerogen: from types to models of chemical structure. Oil & gas science and technology, 58(2), 243-269.

Zelenko, Yu. M., Dziuba, O. V., & Karpenko, O. M. (2016). Spatial distribution of kerogen types based on data pro-cessing of samples by pirolysis method within the Dnieper-Donetsk depression. Geoinformatika, 3 (59), 20-24.

Pavlyuk, М. І. (2014). Geodynamic evolution and oil and gas potential of the Azov-Black Sea and Barents Sea pericontinental shelves [Heodynamichna evolyutsiya ta naftohazonosnistʹ Azovo-Chornomorsʹkoho i Bar-entsevomorsʹkoho perykontynentalʹnykh shelʹfiv]. Lviv, PROMAN LTD, 365.

Mykhailov, V. A., Kurovets, I. M., Senkovskyi, Yu. M., Vyzhva, S. A., Hryhorchuk, K. H., Zahnitko, V. M., Hnidets, V. P., Karpenko, O. M., & Kurovets, S. S. (2014). Unconventional sources of hydrocarbons of Ukraine. Southern oil and gas region [Netradytsiini dzherela vuhlevodniv Ukrainy. Pivdennyi naftohazonosnyi rehion]. Kyiv: VPTs «Kyivskyi universytet», 222.

Koltun, Yu. V. (2008). Evolution of black shale formations and related hydrocarbons generation within the an-cient continental margin of Tethys (Ukrainian Carpathians and adjacent territories) [Evoliutsiia chor-noslantsevykh tovshch ta heneratsiia vuhlevodniv v mezhakh davnoi kontynentalnoi okrainy Tetisu (Ukrainski Karpaty ta sumizhni terytorii)]. Collection of Scientific Works of the Institute of Geological Sciences NAS of Ukraine, 1, 87-92.

Bazhenova, O. K., Fadeeva, N. P., Sent-Zhermes, M. L., Tihomirova, E. E. (2003). Sedimentation Conditions in the Eastern Ocean of Paratethys in the Oligocene – Early Miocene [Usloviya osadkonakopleniya v vostochnom okeane Paratetis v oligotsene–rannem miotsene]. Vestnik MGU. Ser. 4. Geologiya, 6, 12-19.

Khokha Yu. V., Yakovenko M. B., Lyubchak O.V. (2020). Entropy maximization method in thermodynamic model-ling of organic matter evolution at geodynamic regime changing. Geodynamics, 2 (29), 79-88.

Liubchak, O., Khokha, Yu. & Yakovenko, M. (2018). Correlation of the hydrocarbon components structural ele-ments of the Eastern Carpathians argillites by the Jaynes' formalism. Visnyk of V. N. Karazin Kharkiv National University, series "Geology. Geography. Ecology", (49), 83-94.

Behar, F., Lorant, F., & Lewan, M. (2008). Role of NSO compounds during primary cracking of a Type II kerogen and a Type III lignite. Organic Geochemistry, 39(1), 1-22.

Helgeson, H. C., Richard, L., McKenzie, W. F., Norton, D. L., & Schmitt, A. (2009). A chemical and thermodynamic model of oil generation in hydrocarbon source rocks. Geochimica et Cosmochimica Acta, 73(3), 594-695.

Bell I.H., Wronski, J., Quoilin, S., & Lemort, V. (2014). Pure and Pseudo-pure Fluid Thermophysical Property Eval-uation and the Open-Source Thermophysical Property Library CoolProp. Industrial & Engineering Chemistry Research, 53(6), 2498-2508.

Liubchak, O., Khokha, Yu. & Yakovenko, M. (2019). Thermodynamics of type II kerogen transformation. Geology & Geochemistry of Combustible Minerals, 3 (180), 25–40.

Lindsey, A.S., & Jeskey, H. (1957). The Kolbe-Schmitt Reaction. Chemical Reviews, 57 (4), 583-620.

How to Cite
Любчак, О., Павлюк, М., Хоха, Ю., & Яковенко, М. (2021). Modeling the transformation of І and ІІІ types kerogen by the method of entropy maximization. Visnyk of V. N. Karazin Kharkiv National University, Series "Geology. Geography. Ecology", (54), 83-95.