In this study, a self-designed test system for injecting water vapour was used to pyrolyse oil shale from Barkol, Xinjiang, China. The internal structure of oil shale samples after water vapour pyrolysis at different temperatures was characterised using micro-computed tomography (micro-CT). The results showed that under the action of high-temperature water vapour, oil shale underwent evident thermal cracking and pyrolysis, and the porosity increased from 0.08% of the original state to 16.73% at 550 °C. At 300 °C, the maximum pore group was distributed along the bedding plane due to the influence of thermal cracking, and the equivalent diameter was 1201.73 μm. When the water vapour temperature increased from 300 °C to 400 °C, the organic matter at a low boiling point in oil shale began to pyrolyse, forming several pores. These pores were gradually connected with adjacent fractures. The pores with an equivalent diameter of approximately100–500 μm in oil shale accounted for > 60% of the total pore volume. The maximum pore cluster expanded perpendicular to the bedding plane, but there was still no effective seepage channel. With an increase in the water vapour temperature, the large-scale pyrolysis of organic matter began and the pores and fractures in oil shale were continuously generated and gradually connected; at 450 °C, the seepage channel connecting the entire digital core area began to form. At 550 °C, the equivalent diameter of the maximum pore group reached 5756.72 μm, accounting for 69.65% of the total pore volume.
1. Demirbas, A., Alidrisi, H., Balubaid, M. A. API gravity, sulfur content, and desulfurization of crude oil. Petrol. Sci. Technol., 2015, 33(1), 93‒101.
https://doi.org/10.1080/10916466.2014.950383
2. Washburn, K. E., Birdwell, J. E., Foster, M., Gutierrez, F. Detailed description of oil shale organic and mineralogical heterogeneity via Fourier transform infrared microscopy. Energy Fuels, 2015, 29(7), 4264‒4271.
https://doi.org/10.1021/acs.energyfuels.5b00807
3. Dyni, J. R. Geology and resources of some world oil-shale deposits. Oil Shale, 2003, 20(3), 193‒252.
4. Al-Ayed, O. S., Suliman, M. R., Rahman, N. A. Kinetic modeling of liquid generation from oil shale in fixed bed retort. Appl. Energy, 2010, 87(7), 2273‒2277.
https://doi.org/10.1016/j.apenergy.2010.02.006
5. Tong, J. H., Jiang, X. M., Han, X. X., Wang, X. Y. Evaluation of the macro-molecular structure of Huadian oil shale kerogen using molecular modeling. Fuel, 2016, 181, 330‒339.
https://doi.org/10.1016/j.fuel.2016.04.139
6. Niu, M. T., Wang, S., Han, X. X., Jiang, X. M. Yield and characteristics of shale oil from the retorting of oil shale and fine oil-shale ash mixtures. Appl. Energy, 2013, 111, 234‒239.
https://doi.org/10.1016/j.apenergy.2013.04.089
7. Demirbas, A. Conversion of oil shale to liquid hydrocarbons. Energ. Source. Part A, 2016, 38(18), 2698‒2703.
https://doi.org/10.1080/15567036.2015.1115925
8. Liu, Z. J., Meng, Q. T., Dong, Q. S., Zhu, J. W., Guo, W., Ye, S. Q., Liu, R., Jia, J. L. Characteristics and resource potential of oil shale in China. Oil Shale, 2017, 34(1), 15‒41.
https://doi.org/10.3176/oil.2017.1.02
9. Liu, Z. J., Dong, Q. S., Ye, S. Q., Zhu, J. W., Guo, W., Li, D. C., Liu, R., Zhang, H. L., Du, J. F. The situation of oil shale resources in China. Journal of Jilin University (Earth Science Edition), 2006, 36(6), 869‒876 (in Chinese).
10. Deng, S. H., Wang, Z. J., Gu, Q., Meng, F. Y., Li, J. F., Wang, H. Y. Extracting hydrocarbons from Huadian oil shale by sub-critical water. Fuel Process. Technol., 2011, 92(5), 1062‒1067.
https://doi.org/10.1016/j.fuproc.2011.01.001
11. Selberg, A., Viik, M., Pall, P., Tenno, T. Environmental impact of closing of oil shale mines on river water quality in North-Eastern Estonia. Oil Shale, 2009, 26(2), 169‒183.
https://doi.org/10.3176/oil.2009.2.09
12. Tohver, T. Utilization of waste rock from oil shale mining. Oil Shale, 2010, 27(4), 321‒330.
https://doi.org/10.3176/oil.2010.4.05
13. Sun, Y. H., Guo, W., Deng, S. H. The status and development trend of in-situ conversion and drilling exploitation technology for oil shale. Drilling Engineering, 2021, 48(01), 57‒67 (in Chinese).
14. Kang, Z. Q., Zhao, Y. S., Yang, D., Tian, L. J., Li, X. A pilot investigation of pyrolysis from oil and gas extraction from oil shale by in-situsuperheated steam injection. J. Petrol. Sci. Eng., 2020, 186, 106785.
https://doi.org/10.1016/j.petrol.2019.106785
15. Sun, Y. H., Kang, S. J., Wang, S. Y., He, L., Guo, W., Li, Q., Deng, S. H. Subcritical water extraction of Huadian oil shale at 300 °C. Energy Fuels, 2019, 33(3), 2106‒2114.
https://doi.org/10.1021/acs.energyfuels.8b04431
16. Lei, J., Pan, B. Z., Guo, Y. H., Fan, Y. F., Xue, L. F., Deng, S. H., Zhang, L. H., Ruhan, A. A comprehensive analysis of the pyrolysis effects on oil shale pore structures at multiscale using different measurement methods. Energy, 2021, 227, 120359.
https://doi.org/10.1016/j.energy.2021.120359
17. Saif, T., Lin, Q. Y., Singh, K., Bijeljic, B., Blunt, M. J. Dynamic imaging of oil shale pyrolysis using synchrotron x-ray microtomography. Geophys. Res. Lett., 2016, 43(13), 6799‒6807.
https://doi.org/10.1002/2016GL069279
18. Zhao, J. P., Dong, X., Zhang, J. Y., Chen, H., Zhang, W. J. A 3D FIB-SEM technique for quantitative characterization of oil shale’s microstructure: A case study from the Shahejie Formation in Dongying Depression, China. Energy Sci. Eng., 2021, 9(1), 116‒128.
https://doi.org/10.1002/ese3.819
19. Li, G. Y., Ma, Z. L., Zheng, J. X., Bao, F., Zheng, L. J. NMR analysis of the physical change of oil shales during in situ pyrolysis at different temperatures. Petroleum Geology and Experiment, 2016, 38(3), 402‒406 (in Chinese).
20. Yang, L. S., Yang, D., Zhao, J., Liu, Z. H., Kang, Z. Q. Changes of oil shale pore structure and permeability at different temperatures. Oil Shale, 2016, 33(2), 101‒110.
https://doi.org/10.3176/oil.2016.2.01
21. Mozaffari, S., Järvik, O., Baird, Z. S. Effect of N2 and CO2 on shale oil from pyrolysis of Estonian oil shale. International Journal of Coal Preparation and Utilization, 2021.
https://doi.org/10.1080/19392699.2021.1914025
22. Yang, D., Wang, L., Zhao, Y. S., Kang, Z. Q. Investigating pilot test of oil shale pyrolysis and oil and gas upgrading by water vapor injection. J. Petrol. Sci. Eng., 2021, 196, 108101.
https://doi.org/10.1016/j.petrol.2020.108101
23. Zhang, M. Q., Liu, Z. J., Sun, P. C., Wang, J. X., Li, Y. J., Hou, L. Y. Well logging identification of Lower Jurassic Badaowan Formation oil shale in Dachanggou Basin, Xinjiang. Coal Geology of China, 2020, 32(6), 27‒35 (in Chinese).
24. Wang, J. X., Sun, P. C., Liu, Z. J., Li, Y. J. Characteristics and genesis of lacustrine laminar coal and oil shale: A case study in the Dachanggou Basin, Xinjiang, Northwest China. Mar. Petrol. Geol., 2021, 126, 104924.
https://doi.org/10.1016/j.marpetgeo.2021.104924
