Formation of synthetic structures and textures of rocks when simulating in COMSOL Multiphysics

Rock texture and structure play an important role in the formation of the rock physical properties, and also carry information about their genesis. The paper deals with the simulation of geometric shapes of various structures and textures of rocks by the finite-element method (FEM). It is carried out by programmed detailing of the element properties and their spatial location in the simulated object. When programming structures, it is also possible to set the physical properties of various parts of the model, grids, initial and boundary conditions, which can be changed in accordance with the scenarios for numerical experiments. In this study, on the basis of FEM, simulation of various structures and textures of rocks with inclusions and disruptions was implemented in COMSOL Multiphysics in conjunction with Matlab. Such structures are used to conduct computer generated simulations to determine physical properties of geomaterials and study the effect on them of agents of various physical nature. The building of several models was considered: a rock specimen with inclusions in the form of ellipses of equal dimensions with different orientations; a sandstone specimen containing inclusions with high modulus of elasticity in cement matrix when deforming; a limestone specimen with fractures filled with oil and saline water when determining its specific electrical resistance. As an example of a fractured structure analysis, the influence of the filler on the electrical resistance of the limestone specimen containing a system of thin elliptical predominantly horizontal fractures was considered. The change in the lines of current flow at different ratios between the matrix and the fracture filler conductivities and their effect on the effective (averaged) conductivity of the rock specimen was clearly demonstrated. The lower conductivity of the fracture filler leads to increasing the length and decreasing the cross-section of the current flow lines that, in turn, leads to significant decrease in the conductivity of the fractured rock specimen. The higher filler conductivity results in a slight increase in the conductivity of the fractured specimen compared to that of the homogeneous isotropic specimen. The resulting structures can be used for numerical experiments to study physical properties of rocks.

1. Ivankina T. I., Matthies S. On the development of the quantitative texture analysis and its application in solving problems of the Earth sciences. Physics of Particles and Nuclei. 2015;46:366–423. https://doi.org/10.1134/S1063779615030077

2. Daryono L. R., Titisari A. D., Warmada I. W., Kawasaki S. Comparative characteristics of cement materials in natural and artificial beachrocks using a petrographic method. Bulletin of Engineering Geology and the Environment. 2019;78:3943–3958. https://doi.org/10.1007/s10064-018-1355-x

3. Nachev V. A., Kazak A. V., Turuntaev S. B. 3D digital mineral-mechanical modeling of complex reservoirs rocks for understanding fracture propagation at microscale. In: Society of Petroleum Engineers – SPE Russian Petroleum Technology Conference 2020, RPTC 2020. Society of Petroleum Engineers; 2020. https://doi.org/10.2118/201979-MS

4. Sangirardi M., Malena M., de Felice G. Settlement induced crack pattern prediction through the jointed masonry model. In: Carcaterra A., Paolone A., Graziani G. (eds.) Proceedings of XXIV AIMETA Conference 2019. AIMETA 2019. Lecture Notes in Mechanical Engineering. Springer, Cham. 2020. https://doi.org/10.1007/978-3-030-41057-5_158

5. Bradbury K. K., Davis C. R., Shervais J. W., Janecke S. U., Evans J. P. Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions. Pure and Applied Geophysics. 2015;172:1053–1078. https://doi.org/10.1007/s00024-014-0896-6

6. Nikitin A. N., Ivankina T. I., Ullemeyer K., Vasin R. N. Similar quartz crystallographic textures in rocks of continental earth’s crust (by neutron diffraction data): II. Quartz textures in monophase rocks. Crystallography Reports. 2008;53:819–827. https://doi.org/10.1134/S1063774508050167

7. Abd Elmola A., Charpentier D., Buatier M., Lanari P., Monié P. Textural-chemical changes and deformation conditions registered by phyllosilicates in a fault zone (Pic de Port Vieux thrust, Pyrenees). Applied Clay Science. 2017;144:88–103. https://doi.org/10.1016/j.clay.2017.05.008

8. Allo F. Consolidating rock-physics classics: A practical take on granular effective medium models. The Leading Edge. 2019;38(5):334–40. https://doi.org/10.1190/tle38050334.1

9. Hu X., Huang S. Physical Properties of Reservoir Rocks. In: Hu X., Hu S., Jin F., Huang S. (eds) Physics of Petroleum Reservoirs. Springer Geophysics. Springer, Berlin, Heidelberg. 2017. https://doi.org/10.1007/978-3-662-55026-7_2

10. Frischbutter A., Janssen C., Scheffzük C., Walther K., Ullemeyer K., Behrmann J. H., et al. Strain and texture measurements on geological samples using neutron diffraction at IBR-2, Joint Institute for Nuclear Research, Dubna (Russia). Physics of Particles and Nuclei. 2006;37:S45–S68. https://doi.org/10.1134/S1063779606070033

11. Hudleston PJ, Lan L. Rheological information from geological structures. Pure and Applied Geophysics. 1995;145:605–620. https://doi.org/10.1007/BF00879591

12. Howarth D. F., Rowlands J. C. Development of an index to quantify rock texture for qualitative assessment of intact rock properties. Geotechnical Testing Journal. 1986;9(4):169–179. https://doi.org/10.1520/GTJ10627J

13. Howarth D. F., Rowlands J. C. Quantitative assessment of rock texture and correlation with drillability and strength properties. Rock Mechanics and Rock Engineering. 1987;20:57–85. https://doi.org/10.1007/BF01019511

14. Azzoni A., Bailo F., Rondena E., Zaninetti A. Assessment of texture coefficient for different rock types and correlation with uniaxial compressive strength and rock weathering. Rock Mechanics and Rock Engineering. 1996;29:39–46. https://doi.org/10.1007/BF01019938

15. Kamani M., Ajalloeian R. Evaluation of Engineering Properties of Some Carbonate Rocks Trough Corrected Texture Coefficient. Geotechnical and Geological Engineering. 2019 Apr 15;37:599–614. https://doi. org/10.1007/s10706-018-0630-8

16. Ajalloeian R, Mansouri H, Baradaran E. Some carbonate rock texture effects on mechanical behavior, based on Koohrang tunnel data, Iran. Bulletin of Engineering Geology and the Environment. 2017;76:295–307. https://doi.org/10.1007/s10064-016-0861-y

17. Ömer Ü., Florian A. Influence of micro-texture on the geo-engineering properties of low porosity volcanic rocks. In: Engineering Geology for Society and Territory – Volume 6: Applied Geology for Major Engineering Projects. Springer International Publishing; 2015. P. 69–72. https://doi.org/10.1007/978-3-319-09060-3_12

18. Song R., Zheng L., Wang Y., Liu J. Effects of Pore Structure on Sandstone Mechanical Properties Based on Micro-CT Reconstruction Model. Advances in Civil Engineering. 2020;2020: 9085045. https://doi.org/10.1155/2020/9085045

19. Zhou J., Zhang L., Yang D., Braun A., Han Z. Investigation of the quasi-brittle failure of alashan granite viewed from laboratory experiments and grain-based discrete element modeling. Materials (Basel). 2017;10(7):835. https://doi.org/10.3390/ma10070835

20. Zhao X., Wang T., Elsworth D., He Y., Zhou W., Zhuang L., et al. Controls of natural fractures on the texture of hydraulic fractures in rock. Journal of Petroleum Science and Engineering. 2018;165:616–626. https://doi.org/10.1016/j.petrol.2018.02.047

21. Rahimi M. R., Mohammadi S. D., Beydokhti A. T. Effects of Mineral Composition and Texture on Durability of Sulfate Rocks in Gachsaran Formation, Iran. Geotechnical and Geological Engineering. 2020;38:2619–2637. https://doi.org/10.1007/s10706-019-01173-9

22. Ozturk C. A., Nasuf E. Strength classifi of rock material based on textural properties. Tunnelling and Underground Space Technology. 2013;37:45–54. https://doi.org/10.1016/j.tust.2013.03.005

23. Wang L. Automatic identification of rocks in thin sections using texture analysis. Mathematical Geology. 1995;27:847–865. https://doi.org/10.1007/BF02087099

24. Prince C. M., Ehrlich R. Analysis of spatial order in sandstones. I. Basic principles. Mathematical Geology. 1990;22:333–359. https://doi.org/10.1007/BF00889892

25. Luthi S. M. Textural segmentation of digital rock images into bedding units using texture energy and cluster labels. Mathematical Geology. 1994;26(2):181–196. https://doi.org/10.1007/BF02082762

26. Ye S. J., Rabiller P., Keskes N. Automatic high resolution texture analysis on borehole imagery. In: SPWLA 39th Annual Logging Symposium 1998. Society of Petrophysicists and Well-Log Analysts (SPWLA); 1998.

27. Wang L. Automatic identification of rocks in thin sections using texture analysis. Mathematical Geology. 1995;27:847–865. https://doi.org/10.1007/BF02087099

28. Xiao H, He L, Li X, Zhang Q, Li W. Texture synthesis: A novel method for generating digital models with heterogeneous diversity of rock materials and its CGM verification. Computers and Geotechnics. 2021;130:103895. https://doi.org/10.1016/j.compgeo.2020.103895

29. Algive L, Bekri S, Lerat O, Nader F, Vizika O. Reactive pore network modeling technology to evaluate the impact of diagenesis on the petrophysical properties of a rock. In: Society of Petroleum Engineers – International Petroleum Technology Conference 2009, IPTC 2009. 2009, pp. 3452–3461. https://doi.org/10.3997/2214-4609-pdb.151.iptc14049

30. Kazerani T, Nilipour N, Garin E, Seingre G. Application of numerical modelling for large-scale underground excavation in foliated rock mass. In: ISRM Regional Symposium, EUROCK 2015. International Society for Rock Mechanics; 2015, pp. 931–936.

31. Coelho G., Branquet Y., Sizaret S., Arbaret L., Champallier R., Rozenbaum O. Permeability of sheeted dykes beneath oceanic ridges: Strain experiments coupled with 3D numerical modeling of the Troodos Ophiolite, Cyprus. Tectonophysics. 2015;644:138–150. https://doi.org/10.1016/j.tecto.2015.01.004