The micron-scale (µm) pore is the main channel of fluid percolation. The evolution of µm-sized pore structures in a cylindrical oil shale sample (φ = 0.82 × 7 mm) at different temperatures was investigated by high-precision micro-computed tomography (micro-CT) scan technology. It is found that there is a small change in pore structure when the temperature is lower than 300 °C. However, the quantity and average diameter of pores as well as porosity are all dramatically enhanced when the temperature ranges from 300 to 400 °C, and each parameter attains a maximum value when the temperature reaches 500 °C. This can be expected from the formation of a great amount of oil and gases through pyrolysis of solid organic matter at higher temperature. And so the spaces previously occupied by organic matter become the ones filled with pores.
The newly-formed pores can be taken as the valid channels connecting the original pores. This is attested by the decrease in the quantity of pores with a diameter of 0.54–1.50 μm and the slight increase in the amount of pores having a diameter from 1.70 to 4.10 μm. Thus, the coalescence of µm-sized pores enlarged the channels facilitating the fluid percolation, in favor of the injection of heated fluids and the release of oil and gases during pyrolysis.
1. Qian, J. L., Yin, L., Li, S. Y. Oil Shale – Petroleum Alternative. China Petrochemical Press, Beijing, 2010.
2. Li, S. Y., Ma, Y., Qian, J. L. Global oil shale research, development and utilization today and an overview of three oil shale symposiums in 2011. Sino-Global Energy, 2012, 17(2), 8–17 (in Chinese).
3. Dyni, J. R. Geology and resources of some world oil-shale deposits. Oil Shale, 2003，20(3), 193–252.
4. Li, S. Y., Yue, C. T. Study of pyrolysis kinetics of oil shale. Fuel, 2003, 82(3), 337–342.
https://doi.org/10.1016/S0016-2361(02)00268-5
5. Li, S. Y., Yue, C. T. Study of different kinetic models for oil shale pyrolysis. Fuel Process. Technol., 2004, 85(1), 51–61.
https://doi.org/10.1016/S0378-3820(03)00097-3
6. El harfi, K., Mokhlisse, A., Chanaa, M. B., Outzourhit, A. Pyrolysis of Moroccan (Tarfaya) oil shales under microwave irradiation. Fuel, 2000, 79(7), 733–742.
https://doi.org/10.1016/S0016-2361(99)00209-4
7. Razvigorova, M., Budinova, T., Petrova, B., Tsyntsarski, B., Kinci, E., Ferhat, M. F. Steam pyrolysis of Bulgarian oil shale kerogen. Oil Shale, 2008, 25(1), 27–36.
https://doi.org/10.3176/oil.2008.1.04
8. Kök, M. V., Guner, G., Bagci, S. Laboratory steam injection applications for oil shale fields of Turkey. Oil Shale, 2008, 25(1), 37–46.
https://doi.org/10.3176/oil.2008.1.05
9. Kang, Z. Q., Lu, Z. X., Yang, D., Zhao, Y. S. The solid-fluid-thermal-chemistry coupling mathematical model for oil shale in-situ steam injecting development. Journal of Xian Shiyou University, 2008, 23(4), 30–34 (in Chinese).
10. Zheng, D. W., Li, S. Y., Ma, G. L., Wang, H. Y. Autoclave pyrolysis experiments of Chinese Liushuhe oil shale to simulate in-situ underground thermal conversion. Oil Shale, 2012, 29(2), 103–114.
https://doi.org/10.3176/oil.2012.2.02
11. Kang, Z. Q., Yang, D., Zhao, Y. S., Hu, Y. Q. Thermal cracking and corresponding permeability of Fushun oil shale. Oil Shale, 2011, 28(2), 273–283.
https://doi.org/10.3176/oil.2011.2.02
12. Zhao, J., Yang, D., Kang, Z. Q., Feng, Z. C. A micro-CT study of changes in the internal structure of Daqing and Yan'an oil shales at high temperatures. Oil Shale, 2012, 29(4), 357–367.
https://doi.org/10.3176/oil.2012.4.06
13. Saif, T., Lin, Q. Y., Singh, K., Bijeljic, B., Blunt, M. 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
14. Tiwari, P., Deo, M., Lin, C. L., Miller, J. D. Characterization of oil shale pore structure before and after pyrolysis by using X-ray micro CT. Fuel, 2013, 107, 547–554.
https://doi.org/10.1016/j.fuel.2013.01.006
15. Sun, L. N., Tuo, J. C., Zhang, M. F., Wu, C. J., Wang, Z. X., Zheng, Y. W. Formation and development of the pore structure in Chang 7 member oil-shale from Ordos Basin during organic matter evolution induced by hydrous pyrolysis. Fuel, 2013, 158, 549–557.
https://doi.org/10.1016/j.fuel.2015.05.061
16. Clarkson, C. R., Solano, N., Bustin, R. M., Bustin. A. M. M., Chalmers, G. R. L., He, L., Melnichenko, Y. B., Radinski, A. P., Blach, T. P. Pore structure characterization of North American shale gas reservoirs using USANS/SANS, gas adsorption, and mercury intrusion. Fuel, 2013, 103, 606–616.
https://doi.org/10.1016/j.fuel.2012.06.119
17. Han, X. X., Jiang, X. M., Yu, L. J., Cui, Z. G. Change of pore structure of oil shale particles during combustion. Part 1. Evolution mechanism. Energ. Fuels, 2006, 20(6), 2408–2412.
https://doi.org/10.1021/ef0603277
18. Sedman, A., Talviste, P., Kirsimäe, K. The study of hydration and carbonation reactions and corresponding changes in the physical properties of co-deposited oil shale ash and semicoke wastes in a small-scale field experiment. Oil Shale, 2012, 29(3), 279–294.
https://doi.org/10.3176/oil.2012.3.07
19. Mõtlep, R., Kirsimäe, K., Talviste, P., Puura, E., Jürgenson, J. Mineral composition of Estonian oil shale semi-coke sediments. Oil Shale, 2007, 24(3), 405–422.
20. Shi, Y. Y., Li, S. Y., Ma, Y., Yue, C. T., Shang, W. Z., Hu, H. Q., He, J. L. Pyrolysis of Yaojie oil shale in a Sanjiang-type pilot-scale retort. Oil Shale, 2012, 29(4), 368–375.https://doi.org/10.3176/oil.2012.4.07
