Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression
Abstract
:1. Introduction
2. Specimen Preparation and Experimental Procedure
2.1. Testing Device
2.2. Specimen Preparation
2.3. Experimental Procedure
3. Results and Discussion
3.1. Micro Structure and Mineral Composition
3.2. Mechanical Property Measurements
3.3. Cracks Propagation Analysis
3.3.1. 0° Orientation
3.3.2. 90° Orientation
3.4. Quantitative Characterization of Cracks
3.4.1. Crack SSA and Tortuosity
3.4.2. Crack Fractal Dimension
4. Conclusions
- (1)
- The Longmaxi shale specimens are characterized by a high content (88.49 wt %) of brittle minerals and low porosity (organic matter and pores account for about 2.66%), as tested by mineral composition analysis on a 300 μm × 300 μm region of a BSE image using AMICS. The mineral grains are highly compacted and are distributed in laminae. During uniaxial compression, the Longmaxi shale does not have any inelastic range on the stress-stain curve, showing typical brittle fracture characteristics. The UCS values of shale show great variation, ranging from 103.52 to 174.63 MPa, probably caused by the heterogeneity of structure and mineral composition at millimeter-scale.
- (2)
- The micro-CT images during loading can reflect the evolution of the micro-/meso-cracks in the shale specimens. At 0° orientation, the fracture begins with a single crack, which then expands and bifurcates into many secondary cracks. As loading stress increases, more micro cracks develop and gradually connect to the primary crack or form new cracks, some of which cut through the specimen, mainly as tension cracks. In the specimens at 90° orientation, the first crack appears throughout the specimen, though not vertically. More cracks cross or join during the loading process as tension-shear cracks oriented at an angle of about 70° to the horizontal direction, with a few parallel cracks occurring along the weak consolidated bedding planes. The average thickness of cracks at 90° orientation is higher than that of 0°.
- (3)
- The loading force at which the initial crack occurred is dependent upon the orientation. The initial cracks at 90° orientation were observed to occur at higher loading forces, and later than that at 0° orientation, and most appeared close to peak strength.
- (4)
- The quantitative characterization of cracks was conducted on the segmented and binary CT scan images. The specific surface area per volume and tortuosity are positively correlated at different loading stages. The crack images from CT scan have obvious fractal characteristics. The 3-D BCD increased as crack propagation progressed, and can be used as a quantitative parameter of the crack evolution. Furthermore, the 3-D BCD for 0° bedding orientation is 2.44 and 2.38, lower than the 90° bedding orientations of 2.53 and 2.50. The results suggest that the cracks produced in the 90° bedding orientation specimen is more complex than that of 0° orientation, due to the crossed secondary cracks.
Author Contributions
Acknowledgments
Conflicts of Interest
References
- Rine, J.M.; Smart, E.; Dorsey, W.; Hooghan, K.; Dixon, M. Comparison of porosity distribution within selected North American shale units by SEM examination of Argon-ion-milled specimens. AAPG Mem. 2013, 102, 137–152. [Google Scholar]
- Yaritani, H.; Matsushima, J. Analysis of the energy balance of shale gas development. Energies 2014, 7, 2207–2227. [Google Scholar] [CrossRef]
- Aruga, K. The U.S. shale gas revolution and its effect on international gas markets. J. Unconv. Oil Gas Res. 2016, 14, 1–5. [Google Scholar] [CrossRef]
- Yang, Q.; Carlos, T.V. Joint interpretation and uncertainty analysis of petrophysical properties in unconventional shale reservoir. Interpretation 2014, 3, 33–49. [Google Scholar] [CrossRef]
- Wu, Y.; Li, X.; He, J.; Zheng, B.; Sciubba, E. Mechanical properties of Longmaxi black organic-rich shale samples from South China under uniaxial and triaxial compression states. Energies 2016, 9, 1088. [Google Scholar] [CrossRef]
- Cho, J.W.; Kim, H.; Jeon, S.; Min, K.B. Deformation and strength anisotropy of Asan gneiss, Boryeong shale, and Yeoncheon schist. Int. J. Rock Mech. Min. Sci. 2012, 50, 158–169. [Google Scholar] [CrossRef]
- Geng, Z.; Chen, M.; Yan, J.; Yang, S.; Yi, Z.C.; Fang, X.; Du, X.Y. Experimental study of brittleness anisotropy of shale in triaxial compression. J. Nat. Gas Sci. Eng. 2016, 36, 510–518. [Google Scholar] [CrossRef]
- He, S.; Wang, W.; Shen, H.; Tang, M.; Liang, H.J.; Lu, J.A. Factors influencing wellbore stability during underbalanced drilling of horizontal well: When fluid seepage is considered. J. Nat. Gas Sci. Eng. 2015, 23, 80–89. [Google Scholar] [CrossRef]
- Amann, F.; Kaiser, P.; Button, E.A. Experimental study of brittle behavior of clay shale in rapid triaxial compression. Rock Mech. Rock Eng. 2012, 45, 21–33. [Google Scholar] [CrossRef]
- Hanna, K.; Insun, S.; Ki-Bok, M. Anisotropy of elastic moduli, P-wave velocities, and thermal conductivities of Asan gneiss, Boryeong shale, and Yeoncheon schist in Korea. Eng. Geol. 2012, 147, 68–77. [Google Scholar]
- Kuila, U.; Dewhurst, D.N.; Siggins, A.F.; Raven, M.D. Stress anisotropy and velocity anisotropy in low porosity shale. Tectonophysics 2011, 503, 34–44. [Google Scholar] [CrossRef]
- Xue, L.; Qin, S.Q.; Sun, Q.; Wang, Y.Y.; Qian, H.T. A quantitative criterion to describe the deformation process of rock specimen subjected to uniaxial compression: From criticality to final failure. Physica A 2014, 410, 470–482. [Google Scholar] [CrossRef]
- Yan, C.L.; Deng, J.G.; Hu, L.B.; Chen, Z.J.; Yan, X.J.; Lin, H.; Tan, Q.; Yu, B.H. Brittle failure of shale under uniaxial compression. Arab. J. Geosci. 2015, 8, 2467–2475. [Google Scholar]
- Hou, P.; Gao, F.; Yang, Y.G.; Zhang, X.X.; Zhang, Z.Z. Effect of the layer orientation on mechanics and energy evolution characteristics of shales under uniaxial loading. Int. J. Min. Sci. Technol. 2016, 26, 857–862. [Google Scholar] [CrossRef]
- Janeiro, R.P.; Einstein, H.H. Experimental study of the cracking behavior of specimens containing inclusions (under uniaxial compression). Int. J. Fract. 2010, 164, 83–102. [Google Scholar] [CrossRef]
- Kong, B.; Wang, E.Y.; Li, Z.H.; Wang, X.R.; Liu, X.F.; Nan, L.; Yang, T.L. Electromagnetic radiation characteristics and mechanical properties of deformed and fractured sandstone after high temperature treatment. Eng. Geol. 2016, 209, 82–92. [Google Scholar] [CrossRef]
- Safari, R.; Ghassemi, A. 3-D thermo-poroelastic analysis of fracture network deformation and induced micro-seismicity in enhanced geothermal systems. Geothermics 2015, 58, 1–14. [Google Scholar] [CrossRef]
- Wu, L.X.; Geng, N.G.; Wang, J.H.; Cui, C.Y. Remote sensing rock mechanics (RSRM) and associated experimental studies. Int. J. Rock Mech. Min. Sci. 2000, 37, 879–888. [Google Scholar] [CrossRef]
- Wu, Z.H.; Zuo, Y.J.; Wang, S.Y. Numerical simulation and fractal analysis of mesoscopic scale failurein shale using digital images. J. Petrol. Sci. Eng. 2016, 145, 592–599. [Google Scholar] [CrossRef]
- Xie, H.P.; Liu, J.F.; Ju, Y.; Li, J.; Xie, L.Z. Fractal property of spatial distribution of acoustic emissions during the failure process of bedded rock salt. Int. J. Rock Mech. Min. Sci. 2011, 48, 1344–1351. [Google Scholar] [CrossRef]
- Zhang, X.; Lu, Y.; Tang, J.; Zhou, Z.; Liao, Y. Experimental study on fracture initiation and propagation in shale using supercritical carbon dioxide fracturing. Fuel 2017, 190, 370–378. [Google Scholar] [CrossRef]
- Ge, X.R.; Ren, J.X. Real-in time CT test of the rock meso-damage propagation law. Sci. China (Ser. E) 2000, 1, 104–111. [Google Scholar] [CrossRef]
- Kim, K.Y.; Zhuang, L.; Yang, H.; Kim, H.; Min, K.B. Strength anisotropy of Berea sandstone: Results of X-ray computed tomography, compression tests, and discrete modeling. Rock Mech. Rock Eng. 2016, 49, 1201–1210. [Google Scholar] [CrossRef]
- Liu, J.H.; Jiang, Y.D.; Zhao, Y.X.; Zhu, J. Uniaxial compression CT and acoustic emission test on the coal crack propagation destruction process. J. Coal. Sci. Eng. 2013, 19, 69–74. [Google Scholar] [CrossRef]
- Liu, J.H.; Jiang, Y.D.; Zhao, Y.X. Progress in the application of AE and CT in research of coal and rock fracture propagation. Met. Mine 2008, 10, 13–15. [Google Scholar]
- Ma, T.S.; Chen, P. Study of meso-damage characteristics of shale hydration based on CT scanning technology. Pet. Explor. Dev. 2014, 41, 249–256. [Google Scholar] [CrossRef]
- Ma, T.S.; Yang, C.H.; Chen, P.; Wang, X.D.; Guo, Y.T. On the damage constitutive model for hydrated shale using CT scanning technology. J. Nat. Gas Sci. Eng. 2016, 28, 204–214. [Google Scholar] [CrossRef]
- Yang, G.S.; Sun, J.; Xie, D.Y.; Zhang, C.Q.; Pu, Y.B. CT identification of the mechanic characteristics of damage propagation of rock. J. Coal Sci. Eng. 1997, 3, 21–25. [Google Scholar]
- Kawakata, H.; Cho, A.; Kiyama, T.; Yanagidani, T.; Kusunose, K.; Shimada, M. Three-dimensional observations of faulting process in Westerly granite under uniaxial and triaxial conditions by X-ray CT scan. Tectonophysics 1999, 313, 293–305. [Google Scholar] [CrossRef]
- Kawakata, H.; Cho, A.; Yanagidani, T.; Shimada, M. The observations of faulting in Westerly granite under triaxial compression by X-ray CT scan. Int. J. Rock Mech. Min. Sci. 1997, 34, 151–162. [Google Scholar] [CrossRef]
- Sun, W.; Wu, A.X.; Hou, K.P.; Yang, Y.; Liu, L.; Wen, Y.M. Real-time observation of meso-fracture process in backfill body during mine subsidence using X-ray CT under uniaxial compressive conditions. Constr. Build. Mater. 2016, 113, 153–162. [Google Scholar] [CrossRef]
- Li, X.; Duan, Y.T.; Li, S.D.; Zhou, R.Q. Study on the Progressive Failure Characteristics of Longmaxi Shale under Uniaxial Compression Conditions by X-ray Micro-Computed Tomography. Energies 2017, 10, 303. [Google Scholar] [CrossRef]
- Wang, Y.; Li, C.H.; Hao, J.; Zhou, R.Q. X-ray micro-tomography for investigation of meso-structural changes and crack evolution in Longmaxi formation shale during compressive deformation. J. Pet. Sci. Eng. 2018, 164, 278–288. [Google Scholar] [CrossRef]
- Zhou, M.; Yang, J. Effect of the layer orientation on fracture propagation of Longmaxi Shale under uniaxial compression using micro-CT scanning. SEG Tech. Prog. Exp. Abs. 2017, 3920–3924. [Google Scholar] [CrossRef]
- Heng, S.; Guo, Y.T.; Yang, C.H.; Daemen, J.J.K.; Li, Z. Experimental and theoretical study of the anisotropic properties of shale. Int. J. Rock. Mech. Min. Sci. 2015, 74, 58–68. [Google Scholar] [CrossRef]
- Nasseri, M.H.B.; Rao, K.S.; Ramamurthy, T. Failure mechanism in schistose rocks. Int. J. Rock Mech. Min. Sci. 1997, 34, 460. [Google Scholar] [CrossRef]
- Nasseri, M.H.B.; Rao, K.S.; Ramamurthy, T. Anisotropic strength and deformational behavior of Himalayan schists. Int. J. Rock Mech. Min. Sci. 2003, 40, 3–23. [Google Scholar] [CrossRef]
- Niandou, H.; Shao, J.F.; Henry, J.P.; Fourmaintraux, D. Laboratory investigation of the mechanical behaviour of Tournemire shale. Int. J. Rock Mech. Min. Sci. 1997, 34, 3–16. [Google Scholar] [CrossRef]
- Rawling, G.C.; Baud, P.; Wong, T.F. Dilatancy, brittle strength, and anisotropy of foliated rocks: Experimental deformation and micromechanical modeling. J. Geophys. Res. 2002, 107, 1–14. [Google Scholar] [CrossRef]
- Jarvie, D.M.; Hill, R.J.; Ruble, T.E.; Pollastro, R.M. Unconventional shale-gas systems: The Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment. AAPG Bull. 2007, 91, 475–499. [Google Scholar] [CrossRef]
- Gao, C.; Xie, L.Z.; Xie, H.P.; He, B.; Jin, W.C.; Yang, Z.P.; Su, Y.Z. Estimation of the equivalent elastic modulus in shale formation: Theoretical model and experiment. J. Pet. Sci. Eng. 2017, 151, 468–479. [Google Scholar] [CrossRef]
- Wang, Y.; Li, C.H. Investigation of the P- and S-wave velocity anisotropy of a Longmaxi formation shale by real-time ultrasonic and mechanical experiments under uniaxial deformation. J. Pet. Sci. Eng. 2017, 158, 253–267. [Google Scholar] [CrossRef]
- Bazant, Z.P.; Kazemi, M.T.; Hasegawa, T.; Mazars, J. Scale effect in Brazilian split-cylinder test: Measurements and fracture analysis. ACI Mater. J. 1991, 88, 325–332. [Google Scholar]
- Bieniawski, Z.T. The effect of specimen size on compressive strength of coal. Int. J. Rock Mech. Min. Sci. 1968, 5, 325–335. [Google Scholar] [CrossRef]
- Gonzatti, C.; Zorzi, L.; Agostini, I.M.; Fiorentini, J.A.; Viero, A.P.; Philipp, R.P. In situ strength of coal bed based on the size effect study on the uniaxial compressive strength. Int. J. Min. Sci. Technol. 2014, 24, 747–754. [Google Scholar] [CrossRef]
- Li, M.; Mao, X.B.; Lu, A.H.; Tao, J.; Zhang, G.H.; Zhang, L.Y.; Lie, C. Effect of specimen size on energy dissipation characteristics of red sandstone under high strain rate. Int. J. Min. Sci. Technol. 2014, 24, 151–156. [Google Scholar] [CrossRef]
- Medhurst, T.P.; Brown, E.T. A study of the mechanical behavior of coal for pillar design. Int. J. Rock Mech. Min. Sci. 1998, 35, 1087–1105. [Google Scholar] [CrossRef]
- Tiggelaar, R.M.; Verdoold, V.; Eghbali, H.; Desmet, G.; Gardeniers, J.G. Characterization of porous silicon integrated in liquid chromatography chips. Lab Chip 2009, 9, 456–463. [Google Scholar] [CrossRef] [PubMed]
- Heidig, T.; Zeiser, T.; Freund, H. Influence of resolution of rasterized geometries on porosity and specific surface area exemplified for model geometries of porous media. Transp. Porous Media 2017, 120, 1–19. [Google Scholar] [CrossRef]
- Kou, R.; Alafnan, S.F.K.; Akkutlu, I.Y. Multi-scale analysis of gas transport mechanisms in kerogen. Transp. Porous Media 2017, 116, 493–519. [Google Scholar] [CrossRef]
- Qu, G.Z.; Qu, Z.Q.; Hazlett, R.D.; Freed, D.; Mustafayev, R. Geometrical description and permeability calculation about shale tensile micro-fractures. Pet. Explor. Dev. 2016, 43, 124–130. [Google Scholar] [CrossRef]
- Tong, S.Q.; Dong, Y.H.; Zhang, Q.; Elsworth, D.; Liu, S.M. Quantitative analysis of nanopore structural characteristics of lower Paleozoic Shale, Chongqing (Southwestern China): Combining FIB-SEM and NMR Cryoporometry. Energy Fuels 2017, 31, 13317–13328. [Google Scholar] [CrossRef]
- Sarkar, N.; Chaudhuri, B.B. An efficient differential box-counting approach to compute fractal dimension of image. IEEE Trans. Syst. Man Cybern. 1994, 24, 115–120. [Google Scholar] [CrossRef]
- Bouboulis, P.; Dalla, L.; Drakopoulos, V. Construction of recurrent bivariate fractal interpolation surfaces and computation of their box-counting dimension. J. Approx. Theory 2006, 141, 99–117. [Google Scholar]
- Li, J.; Du, Q.; Sun, C. An improved box-counting method for image fractal dimension estimation. Pattern Recognit. 2009, 42, 2460–2469. [Google Scholar]
Orientation | Sample | Height/mm | Diameter/mm | UCS/MPa | E/GPa |
---|---|---|---|---|---|
Axis parallel to the layer | SZA1 | 8.43 | 4.01 | 145.11 | 12.93 |
SZA2 | 8.09 | 4.00 | 174.63 | 12.29 | |
SZA3 | 8.56 | 4.05 | 119.72 | 10.09 | |
SZA4 | 8.52 | 4.02 | 103.52 | 12.31 | |
mean | 8.40 | 4.02 | 135.75 | 11.91 | |
Axis perpendicular to the layer | SZB1 | 8.19 | 4.01 | 128.41 | 11.91 |
SZB2 | 8.46 | 4.02 | 147.35 | 10.53 | |
SZB3 | 8.50 | 4.02 | 107.16 | 8.77 | |
SZB4 | 8.14 | 4.04 | 155.76 | 11.01 | |
mean | 8.32 | 4.02 | 134.67 | 10.56 |
Specimen Number | Load Stress | Quantitative Characterization of Cracks | |||||
---|---|---|---|---|---|---|---|
Volume Percentage/% | Surface Area/µm2 | Volume/µm3 | Specific Surface/1/µm | Tortuosity | Fractal Dimension | ||
SZA3 | 79.58 MPa | 1.14% | 9.25 × 107 | 8.91 × 108 | 0.104 | 1.637 | 2.123 |
103.45 MPa | 1.60% | 1.27 × 108 | 1.16 × 109 | 0.109 | 1.679 | 2.208 | |
119.72 MPa | 6.70% | 3.51 × 108 | 4.96 × 109 | 0.071 | 1.228 | 2.442 | |
SZA4 | 87.54 MPa | / | / | / | / | / | / |
103.52 MPa | 4.95% | 2.37 × 108 | 3.49 × 109 | 0.068 | 1.459 | 2.383 | |
SZB3 | 103.45MPa | 6.02% | 1.63 × 108 | 4.65 × 109 | 0.035 | 1.210 | 2.345 |
107.16 MPa | 14.40% | 4.61 × 108 | 1.07 × 1010 | 0.043 | 1.240 | 2.537 | |
SZB4 | 151.19 MPa | 0.25% | 3.04 × 107 | 2.63 × 108 | 0.115 | 3.336 | / |
155.76 MPa | 6.72% | 2.91 × 108 | 5.01 × 109 | 0.058 | 1.471 | 2.510 |
© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Share and Cite
Zhou, M.; Zhang, Y.; Zhou, R.; Hao, J.; Yang, J. Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression. Energies 2018, 11, 1409. https://doi.org/10.3390/en11061409
Zhou M, Zhang Y, Zhou R, Hao J, Yang J. Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression. Energies. 2018; 11(6):1409. https://doi.org/10.3390/en11061409
Chicago/Turabian StyleZhou, Minyue, Yifei Zhang, Runqing Zhou, Jin Hao, and Jijin Yang. 2018. "Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression" Energies 11, no. 6: 1409. https://doi.org/10.3390/en11061409