Constrain on Oil Recovery Stage during Oil Shale Subcritical Water Extraction Process Based on Carbon Isotope Fractionation Character

Rongsheng Zhao, Luquan Ren, Sunhua Deng, Youhong Sun and Zhiyong Chang
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Rongsheng Zhao: Key Laboratory of Bionic Engineering, College of Biological and Agricultural Engineering, Jilin University, Changchun 130021, China
Luquan Ren: Key Laboratory of Bionic Engineering, College of Biological and Agricultural Engineering, Jilin University, Changchun 130021, China
Sunhua Deng: Key Laboratory of Drilling and Exploitation Technology in Complex Conditions, College of Construction Engineering, Jilin University, Changchun 130021, China
Youhong Sun: School of Engineering and Techology, China University of Geosciences, Beijing 100080, China
Zhiyong Chang: Key Laboratory of Bionic Engineering, College of Biological and Agricultural Engineering, Jilin University, Changchun 130021, China

Energies, 2021, vol. 14, issue 23, 1-12

Abstract: In this work, Huadian oil shale was extracted by subcritical water at 365 °C with a time series (2–100 h) to better investigate the carbon isotope fractionation characteristics and how to use its fractionation characteristics to constrain the oil recovery stage during oil shale in situ exploitation. The results revealed that the maximum generation of oil is 70–100 h, and the secondary cracking is limited. The carbon isotopes of the hydrocarbon gases show a normal sequence, with no “rollover” and “reversals” phenomena, and the existence of alkene gases and the CH 4 -CO 2 -CO diagram implied that neither chemical nor carbon isotopes achieve equilibrium in the C-H-O system. The carbon isotope (C 1 –C 3 ) fractionation before oil generation is mainly related to kinetics of organic matter decomposition, and the thermodynamic equilibrium process is limited; when entering the oil generation area, the effect of the carbon isotope thermodynamic equilibrium process (CH 4 + 2H 2 O ⇄ CO 2 + 4H 2 ) becomes more important than kinetics, and when it exceeds the maximum oil generation stage, the carbon isotope kinetics process becomes more important again. The δ 13 C CO 2 − CH 4 is the result of the competition between kinetics and thermodynamic fractionation during the oil shale pyrolysis process. After oil begins to generate, δ 13 C CO 2 − CH 4 goes from increasing to decreasing (first “turning”); in contrast, when exceeding the maximum oil generation area, it goes from decreasing to increasing (second “turning”). Thus, the second “turning” point can be used to indicate the maximum oil generation area, and it also can be used to help determine when to stop the heating process during oil shale exploitation and lower the production costs.

Keywords: oil shale; subcritical water; pyrolysis; gases; carbon isotope (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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