Journals →  Gornyi Zhurnal →  2021 →  #7 →  Back

ArticleName Thresholding: Application in studies of storage capacity of rocks by X-ray tomography
DOI 10.17580/gzh.2021.07.05
ArticleAuthor Savitsky Ya. V., Galkin S. V.

Perm National Research Polytechnic University, Perm, Russia:

Ya. V. Savitsky, Engineer,
S. V. Galkin, Professor, Doctor of Geological and Mineralogical Sciences


The use of X-ray tomography in the studies of reservoir rocks is usually limited to visualizing the distribution of X-ray density in order to identify large cavities and fractures. The quantitative characterization of poro-perm properties of core samples faces some limitations because of the instrumentation resolution in exposure of standard size samples. Based on the analysis of the X-ray density distribution histograms, the quantitative evaluation method is proposed to distinguish between the solid mineral skeleton and the storage space filled with liquid or gaseous phases. The thresholding process, which determines the boundaries between grains and pores based on density, is a very complicated and fuzzy problem in tomographic studies. The size effect of core samples on the resolving power of X-ray tomography in 3D image reconstruction is analyzed. The porosity coefficients from the tomography data are always lower than the values found by the standard gas-volumetric method, which is explained by the limited resolution of tomographic studies. The differences in the ranges of visible pores in the tomography of cores of different sizes are explained by the higher physical resolution of volumetric images for smaller samples. Namely, the apparent porosity is 0.02 mm on a 5 mm core and 0.03 mm on a 30 mm core. Moreover, in the lower range of pore sizes, tomography allows imaging not all pores but only some fraction of the actual volume of pores. The analysis of average diameter distribution in the binarized images of pores shows that the largest pores, which are mostly involved in fluid flow, stand out well both in the high-resolution images of small size samples and in the images of samples with standard diameter of 30 mm. This result proves the applicability of X-ray tomography in the study of large pores on standard core samples with the possibility of quantitative assessment of their poro-perm properties.
The study was supported by the Ministry of Science and Higher Education of the Russian Federation in the framework of Basic Research Contract No. FSNM-2020-0027 in 2020 and in the panning periods in 2021 and 2022.
The study was carried out using equipment provided by the Share Center for Poro-Perm Properties of Rocks, as well as using unique scientific facility—Rock Storage Capacity Structure Analysis Equipment.

keywords X-ray tomography, rocks, core, pore space structure, porosity, permeability, petrophysics

1. Martyushev D. A., Galkin S. V., Shelepov V. V. The Influence of the Rock Stress State on Matrix and Fracture Permeability under Conditions of Various Lithofacial Zones of the Tournaisian–Fammenian Oil Fields in the Upper Kama Region. Moscow University Geology Bulletin. 2019. Vol. 74, No. 6. pp. 573–581.
2. Andreev N. A., Kazymov K. P. Analysis of compositional and structural changes in clay rocks under the action of agents and inhibitors. Mineralogy, Petrography and Metallogeny – Lectures to the Memory of P. N. Chirvinsky : Collection of Scientific Papers. Perm : PGNIU, 2016. No. 19. pp. 387–389.
3. Galkin S. V., Kolychev I. Yu., Savitskiy Ya. V. Potentialities of investigation of reservoir hydrophobization by compilation of x-ray core tomography and lateral logging. Russian Geology and Geophysics. 2019. Vol. 60, No. 10. pp. 1195–1204.
4. Kornilov A. S., Reymers I. A., Safonov I. V., Yakimchuk I. V. Visualization of quality of 3D tomographic images in construction of digital rock model. Scientific Visualization. 2020. Vol. 12, No. 1. pp. 70–82.
5. Ilchenko V. L. Identification of elastic symmetry elements in anisotropic rock samples by X-ray tomography. Vestnik Instituta geologii Komi nauchnogo tsentra Uralskogo otdeleniya RAN. 2017. No. 9(273). pp. 30–33.
6. Efimov A. A., Galkin S. V., Savitcky Ya. V., Galkin V. I. Estimation of heterogeneity of oil & gas field carbonates reservoirs by means of computer simulation of core X-ray tomography data. Ecology, Environment and Conservation. 2015. Vol. 21, Suppl. Iss. pp. 79–85.
7. Yurkovets D. I., Chernov M. S., Bulygina L. G., Razgulina O. V., Sokolov V. N. X-ray computer tomography to obtain multimedia information on micro/nano structure of clay rocks. Practical MicroTomography : Proceedings of I Russian Conference. Kazan, 2012.
8. Nadeev A. N., Kazak A. V., Varfolomeev I. A., Koroteev D. A., Korobkov D. A. Study of changes in the structure of poorly cemented rock using x-ray micro tomography. Neft. Gaz. Novatsii. 2013. No. 4(171). pp. 23–26.
9. Chugunov S. S., Kazak A. V., Cheremisin A. N. Integration of X-ray micro-computed tomography and focusedion-beam scanning electron microscopy data for pore-scale characterization of Bazhenov formation, Western Siberia. Neftyanoe khozyaystvo. 2015. No. 10. pp. 44–49.
10. Xiao Feng, Jianhui Zeng, Hongbin Zhan, Qinhong Hu, Zhenzhen Ma, Sen Feng. Resolution effect on image-based conventional and tight sandstone pore space reconstructions: Origins and strategies. Journal of Hydrology. 2020. Vol. 586. DOI: 10.1016/j.jhydrol.2020.124856
11. Mahanta B., Vishal V., Ranjith P. G., Singh T. N. An insight into pore-network models of hightemperature heat-treated sandstones using computed tomography. Journal of Natural Gas Science and Engineering. 2020. Vol. 77. DOI: 10.1016/j.jngse.2020.103227
12. Putilov I. S., Gurbatova I. P., Popov N. A., Chizhov D. B., Yurev A. V. Increasing the reliability of results of physical and hydrodynamic tests. Vestnik PNIPU. Geologiya. Neftegazovoe i gornoe delo. 2019. Vol. 19, No . 3. pp. 216–227.
13. Sheng-Qi Yang, Zhen Yang, Hong-Wen Jing, Tao Xu. Fracture evolution mechanism of hollow sandstone under conventional triaxial compression by X-ray micro-CT observations and threedimensional numerical simulations. International Journal of Solids and Structures. 2020. Vol. 190. pp. 156–180.
14. Krivoshchekov S. N., Kochnev A. A. Application experience of computed tomography to study the properties of rocks. Vestnik PNIPU. Geologiya. Neftegazovoe i gornoe delo. 2013. No. 6. pp. 32–42.
15. Pakzad A., Iacoviello F., Ramsey A., Speller R., Griffiths J. et al. Improved X-ray computed tomography reconstruction of the largest fragment of the Antikythera Mechanism, an ancient Greek astronomical calculator. PloS ONE. 201 8. Vol. 13(11). e0207430. DOI: 10.1371/journal.pone.0207430
16. Perevertailo T. G. Influence of sedimentation and post-sedimentation factors on the formation of terrigenous reservoir rock properties. Gornyi Zhurnal. 2012. No. 4. Special issue. pp. 53–55.
17. Elanskiy M. M. Integrated theoretical model of permeability in productive strata with inter-granular voids. Geofizika. 2001. No. 6. pp. 28–37.
18. Kartsev A. A. Hydrogeology of oil and gas reservoirs : Textbook. 2nd edition, revised and enlarged. Moscow : Nedra, 1972. 280 p.

Language of full-text russian
Full content Buy