A method for assigning pre-exponential factors for kerogen kinetics, calibrated with Easy%RoDL, and comparison with EASY%Ro

Abstract

Modeling hydrocarbon-generation processes requires reliable kinetic models for the thermal decomposition of kerogens. To improve confidence and accuracy in modeling of generation, this study employs data from both natural and laboratory maturation to quantify thermal stress and strain for kerogens in 11 source-rock data sets. The method yields kinetic parameters (pre-exponential factor and Ea) for hydrocarbon generation that are constrained to make accurate predictions about thermal stress (quantified here as Ro-equivalent) and thermal strain (quantified as Hydrogen Index) under both laboratory and natural conditions. Methods for converting Tmax values to Ro-equivalents were examined and are discussed briefly. Vitrinite reflectance values were calculated at geological heating rates using the Easy%RoDL kinetic formulation, and were then compared with previous results obtained using EASY%Ro. The large differences observed between the EASY%Ro and Easy%RoDL evaluations are attributed to the differences in the pre-exponential factors in those two Ro-kinetic formulations. Understanding this relationship gives us a way to choose kinetic parameters for hydrocarbon generation that will work well for modeling under geological conditions. The single best A factor for hydrocarbon-generation when using EASY%Ro is 1e13 s−1 , while that for Easy%RoDL is 2e14 s−1 . The minor variation in A factors observed within each of the data sets may or may not be real. Using these results and concepts, more reliable hydrocarbon-generation windows in terms of either Ro-equivalent or Transformation Ratio can be achieved and cross-correlated. These results thus have the potential to increase both the accuracy of hydrocarbon-generation modeling, and the confidence in its results.

Document Type: Perspective

Cited as: Waples, D. W., Yang, S. A method for assigning pre-exponential factors for kerogen kinetics, calibrated with Easy%RoDL, and comparison with EASY%Ro. Advances in Geo-Energy Research, 2023, 7(1): 1-6. https://doi.org/10.46690/ager.2023.01.01

References

Abarghani, A., Ostadhassan, M., Gentzis, T., et al. Correlating Rock-Eval™ Tmax with bitumen reflectance from organic petrology in the Bakken Formation. International Journal of Coal Geology, 2019, 205: 87-104.

Behar, F., Beaumont, V., Penteado, H. L. D. Rock-Eval 6 technology: Performances and developments. Oil & Gas Science and Technology, 2001, 56: 111-134.

Burnham, A. Evolution of vitrinite reflectance models, Presentation to Linked-In Petroleum Systems Analysts. [EB-OL]. 2016-11-2.

Chaouche, A. Geological and geochemical attributes of Paleozoic source rocks and their remaining potential for unconventional resources in Ereg Oriental Algerian Sahara. AAPG Search and Discovery, 2013, 80313: 34.

Espitalié, J. Use of Tmax as a maturation index for different types of organic matter: Comparison with vitrinite reflectance. Collection colloques et séminaires-Institut francais du p ´etrole, 1986, 44: 475-496.

Evenick, J. C. Examining the relationship between Tmax and vitrinite reflectance: An empirical comparison between thermal maturity indicators. Journal of Natural Gas Science and Engineering, 2021, 91: 103946.

Hackley, P. C., Lewan, M. Understanding and distinguishing reflectance measurements of solid bitumen and vitrinite using hydrous pyrolysis: Implications to petroleum assessment. AAPG Bulletin, 2018, 102(6): 1119-1140.

Jarvie, D., Claxton, B., Henk, F., et al. Oil and shale gas from the barnett shale, Ft. worth basin, Texas. Paper Presented at the AAPG National Convention, Denver, Colorado, 3-6 June, 2001.

Katz, B. J., Lin, F. Consideration of the limitations of thermal maturity with respect to vitrinite reflectance, Tmax, and other proxies. AAPG Bulletin, 2021, 105: 695-720.

Lee, H. T., Sun, L. C. Correlation among vitrinite reflectance Ro%, pyrolysis parameters, and atomic H/C ratio: Implications for evaluating petroleum potential of coal and carbonaceous materials. Journal of Energy and Natural Resources, 2014, 3(6): 85-100.

Lewan, M. D., Pawlewicz, M. J. Reevaluation of thermal maturity and stages of petroleum formation of the Mississippian Barnett Shale, Fort Worth Basin, Texas. AAPG Bulletin, 2017, 101(12): 1945-1970.

Mastalerz, M., Hampton, L., Drobniak, A. Thermal Alteration Index (TAI), Vitrinite Reflectance, and Tmax through maturation. Paper Presented at 32nd Annual Meeting of The Society for Organic Petrology, Yogyakarta, Java, Indonesia, 21-27 September, 2015.

Schenk, O., Peters, K., Burnham, A. Evaluation of alternatives to Easy%Ro for calibration of basin and petroleum system models. Paper Presented at 79th EAGE Conference and Exhibition 2017, Paris, France, 12-15 June, 2017.

Snowdon, L. R. Rock-Eval Tmax suppression: Documentation and amelioration. AAPG Bulletin, 1995, 79(9): 1337-1348.

Sweeney, J. J., Burnham, A. K. Evaluation of a simple-model of vitrinite reflectance based on chemical-kinetics. AAPG Bulletin, 1990, 74: 1559-1570.

Veld, H., Fermont, W. J. J., Jergers, L. F. Organic petrological characterization of Westphalian coals from the Netherlands: Correlation between Tmax, vitrinite reflectance and hydrogen index. Organic Geochemistry, 1993, 20(6): 659-675.

Waliczek, M., Machowski, G., Poprawa, P., et al. A novel VRo, T, and S indices conversion formulae on data from the fold-and-thrust belt of the Western Outer Carpathians (Poland). International Journal of Coal Geology, 2021, 234: 103672.

Waples, D. W. Petroleum generation kinetics: Single versus multiple heating-ramp open-system pyrolysis: Discussion. AAPG Bulletin, 2016, 100: 683-689.

Waples, D. W. A calibrated empirical method to choose A factors for kerogen kinetics. Part 1: Using Easy% Ro to calculate thermal stress. Marine and Petroleum Geology, 2022, 141: 105590.

Wust, R. A., Hackley, P. C., Nassichuk, B. R., et al. Vitrinite reflectance versus pyrolysis Tmax data: Assessing thermal maturity in shale plays with special reference to the Duvernay shale play of the Western Canadian Sedimentary Basin, Alberta, Canada. Paper SPE 167031 Presented at SPE Unconventional Resources Conference and Exhibition-Asia Pacific, Brisbane, Australia, 11-13 October, 2013.

Yang, S., Horsfield, B. Critical review of the uncertainty of Tmax in revealing the thermal maturity of organic matter in sedimentary rocks. International Journal of Coal Geology, 2020, 225: 103500.