The article considers the results of 3D basin modeling of the subsalt deposits in Kazakhstan part of the Precaspian basin. Special attention is paid to the kinetic spectrum of kerogen degradation and its effect on the generation time of hydrocarbon fluids in oil and gas source rocks. According to the results of fluid dynamic modeling, the Devonian source rocks began to generate hydrocarbon fluids in the Prekungurian geological period, about 286,8 million years ago. At the turn of the Permian and Triassic time (251,9 million years ago), the degree of transformation of organic matter reached 50 % everywhere. The realization of the potential of the Carboniferous and Permian source rocks began after the accumulation of the Kungurian salt deposits. At the turn of the Permian and Triassic geological time (251,9 million years ago), the main generation center was formed in the Central Caspian depression, local generation occured in the south of the simulated region. Currently, the degree of potential realization for all oil and gas source rocks has a similar distribution. There are two large centeres of generation: in the central part of the Caspian basin and in the south of the simulated area. Laboratory studies of core samples of the Upper Devonian and Lower Permian ages show the presence of deposits rich in organic matter in these age ranges. The obtained kinetic spectrum for these rocks showed a relatively early generation of hydrocarbon fluids from the oil and gas source rocks. Thus, the peak generation for the Lower Permian deposits is observed in the temperature range 125–140 °C, for the Upper Devonian – 130–160 °C. A comparison of the calculation results of basic scenario 1 with standard kinetic spectrum from the TemisFlow™ library and scenario 2 with destruction schemes determined during laboratory studies showed differences in the transformation index of about 2–10 %. It is worth noting that the different reaction rates had the greatest impact on Devonian sediments in the Prekungurian stage of development of the Precaspian oil and gas basin in local areas of the side parts of the depression.
References
1. Emelianenko O.A., Delengov M.T., Ilmukova E.V. et al., Basin modelling of hydrocarbon systems of Pre-Caspian depression (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2023, No. 5, pp. 21-25, DOI: https://doi.org/10.24887/0028-2448-2023-5-21-25
2. Behar F., Vandenbroucke M., Tang Y. et al., Thermal cracking of kerogen in open and closed systems: Determination of kinetic parameters and stoichiometric coefficients for oil and gas generation, Organic Geochemistry, 1997, V. 26, no. 5–6, pp. 321–339, DOI: https://doi.org/10.1016/S0146-6380(97)00014-4
3. Vandenbroucke M., Behar F., Rudkiewicz J.L., Kinetic modelling of petroleum formation and cracking: Implications from the high pressure/high temperature Elgin Field (UK, North Sea), Organic Geochemistry, 1999, V. 30, no. 9, pp. 1105–1125, DOI: https://doi.org/10.1016/S0146-6380(99)00089-3
4. Burnham A.K., Global chemical kinetics of fossil fuels, Springer International Publishing, 2017, 315 p., DOI: https://doi.org/10.1007/978-3-319-49634-4
5. Peters K.E., Burnham A.K., Walters C.C., Petroleum generation kinetics: Single versus multiple heating ramp open-system pyrolysis, AAPG Bulletin, 2015, V. 99, no. 4, pp. 591–616, DOI: http://doi.org/10.1306/01141615146
