An Evaluation Method of Brittleness Characteristics of Shale Based on the Unloading Experiment
Abstract
:1. Introduction
2. Sample Preparation and Test Design
2.1. Triaxial Sample Preparation
2.2. Basic Physical Properties of Shale
2.3. Conventional Triaxial Compression Test of Shale
2.4. Unloading Test Plan
3. Analysis of Test Results
3.1. Analysis of Unloading Experiment
3.1.1. Stress–Strain Curve Analysis of Unloading
3.1.2. Comparative Study on the Stress–Strain Curves of Loading and Unloading
3.2. Influence of Unloading Rate on Shale Mechanical Parameters
3.2.1. Effect of Unloading Rate on Peak Intensity
3.2.2. Influence of Unloading Rate on Destructive Confining Pressure
3.2.3. Effect of Unloading Rate on Residual Stress
3.3. Influence of Unloading Rate on Shale Failure Characteristics
4. Discussion of Rock Brittleness
4.1. Evaluation of Rock Brittleness
4.2. Evaluation of Brittleness during Unloading
4.2.1. Existing Brittleness Evaluation Method
4.2.2. Proposal of Brittleness Evaluation Method Considering Unloading Conditions
4.2.3. Verification of the Brittleness Method and Comparison with Others
5. Conclusions
- (1)
- With the increase of unloading rate , the axial strain and radial strain increases, the radial strain is more significant, and the volumetric strain is reduced gradually, which shows that the dilatancy is weaker. The unloading rate has a strengthening effect on the peak deviatoric stress and has a weakening effect on the residual deviatoric stress and the confining pressure, and there is a typical linear relationship between them. The modulus of elasticity decreases and the logarithm of the peak intensity has a significant linear relationship with the logarithm of the strain rate.
- (2)
- When is 0.05 MPa/s, the shale failure mode is mild, which is a typical single slope shear failure. When is 1.0 MPa/s, the shale fracture morphology is more complicated, the shear fracture surface is increased, and some bedding surface cracks. There are fine vertical distribution cracks between the fracture surfaces, and the shale fracture is sufficient, which shows the simultaneous development of multiple shear zones and synchronous cracking inside the layers, resulting in the overall instability of the shale.
- (3)
- The brittleness evaluation methods are summarized as a total of 33 kinds, and the brittleness of shale samples is well characterized by the brittleness index and during the loading process, they decrease continuously with the increase of confining pressure, which plays a good role in the characterization of the uniaxial failure and the triaxial failure. What is more, compared with , the numerical range of is larger, and the high brittleness characteristics of shale samples under uniaxial compression can be highlighted, which proves the effective application of the method in triaxial loading test.
- (4)
- Aiming at the shortage of and during the unloading process, this paper proposes a brittleness evaluation method based on the unloading stress–strain curve, which can consider the influence of different unloading rates, and there is a good brittleness characterization between the unloading damage and parameter changes of and . This can be related to reservoir geology to analyze the brittleness of the reservoir further, providing a basis for the mining of preferred high brittle blocks and hydraulic fracturing.
Author Contributions
Funding
Conflicts of Interest
Nomenclature
Axial strain, mm/mm | |
Radial strain, mm/mm | |
Volumetric strain, mm/mm | |
Major principal stress, MPa | |
Confining pressure, MPa | |
Axial pressure, MPa | |
Strength coefficient, - | |
Strength coefficient, - | |
Internal friction angle, | |
c | Cohesion, MPa |
Unloading rate, MPa/s | |
The logarithm of unloading rate, - | |
Maximum axial pressure, MPa | |
The logarithm of maximum axial pressure, - | |
Residual stress, MPa | |
The logarithm of residual stress, - | |
Failure confining pressure, MPa | |
The logarithm of failure confining pressure, - | |
Stress drop coefficient, - | |
Softening modulus, - | |
Brittle drop coefficient, - | |
The peak intensity of the sample at point A, MPa | |
Residual strength of the sample at point B, MPa | |
Axial strain of the sample at points A, % | |
Axial strain of the sample at points B, % | |
Axial strain of the sample at points M, % | |
Axial strain of the sample at points U, % | |
Brittleness index, - | |
Brittleness index, - | |
Brittleness index, - | |
Evaluation coefficient, - | |
Evaluation coefficient, - | |
Stress values of point A, MPa | |
Stress values of point B, MPa | |
Stress values of point M, MPa | |
Stress values of point U, MPa | |
Elastic modulus, GPa | |
Poisson’s ratio, - | |
Weights coefficient, - | |
Weights coefficient, - | |
Weights coefficient, - | |
Total elastic modulus, GPa | |
Unloading elastic modulus, GPa | |
Composite coefficient, - | |
Composite coefficient, - | |
Brittleness evaluation index, - | |
Brittleness evaluation index, - |
References
- Guo, X.S. Rules of two-factor enrichment for marine shale gas in Southern China—Understanding from the Longmaxi formation shale gas in Sichuan basin and its surrounding area. Acta Geol. Sin. 2014, 88, 1209–1218. (In Chinese) [Google Scholar] [CrossRef]
- Lyu, Q.; Ranjith, P.G.; Long, X.P.; Ji, B. Experimental investigation of mechanical properties of black shales after CO2-water-rock interaction. Materials 2016, 9, 663. [Google Scholar] [CrossRef] [PubMed]
- Kim, K.; Choe, J. Hydraulic Fracture Design with a Proxy Model for Unconventional Shale Gas Reservoir with Considering Feasibility Study. Energies 2019, 12, 220. [Google Scholar] [CrossRef]
- Energy Information Administration. Shale Gas Production Drives World Natural Gas Production Growth. 2016. Available online: https://www.eia.gov/todayinenergy/detail.php?id=27512 (accessed on 15 August 2016).
- Huo, L.; Yang, C.H.; Liu, J.X.; Mao, H.J.; Huang, W.G. Experimental research on the failure of mudstone cap rock of Western Hubei-Eastern Chongqing suffered uplift and erosion. Chin. J. Undergr. Space Eng. 2018, 14, 33–42. (In Chinese) [Google Scholar]
- Huo, L.; Yang, C.H.; Mao, H.J.; Liu, J.X.; Yuan, X.S. Experimental research on mechanical properties of western Hubei-Eastern Chongqing carbonaceous shale cap rock under unloading stress path. Chin. J. Rock Mech. Eng. 2016, a0135, 2898–2906. (In Chinese) [Google Scholar] [CrossRef]
- Cao, C.R.; Han, C.H.; Zheng, D.R. Impact of structural changes on reservoir preservation. Mar. Geol. Quat. Geol. 2003, 23, 95–98. (In Chinese) [Google Scholar] [CrossRef]
- Li, J.Q.; Gao, Y.Q.; Hua, C.X.; Xia, Z.L. Enlightenment from the experience of shale gas exploration in North America to the establishment of an evaluation system for marine shale gasification area in South China. Pet. Geol. Recovery Effic. 2014, 21, 23–27. (In Chinese) [Google Scholar] [CrossRef]
- Dewhurst, D.N.; Hennig, A.L. Geomechanical properties related to top seal leakage in the Carnarvon Basin, Northwest Shelf, Australia. Pet. Geosci. 2003, 9, 255–263. [Google Scholar] [CrossRef]
- Lewis, H.; Olden, P.; Couples, G.D. Geomechanical simulations of top seal integrity. Nor. Pet. Soc. Spec. Publ. 2002, 11, 75–87. [Google Scholar] [CrossRef]
- Hermanrud, C.; Bols, H.M.; Teige, G.M. Seal failure related to basin-scale processes. AAPG Hedberg Series 2005, 1975, 13–22. [Google Scholar] [CrossRef]
- Teige, G.M.; Hermanrud, C.; Kløvjan, O.S.; Eliassen, P.E.; Løseth, H.; Gading, M. Evaluation of caprock integrity in the western (high-pressured) haltenbanken area—A case history based on analyses of seismic signatures in overburden rocks. Nor. Pet. Soc. Spec. Publ. 2002, 11, 233–242. [Google Scholar] [CrossRef]
- Ogata, K.; Senger, K.; Braathen, A.; Tveranger, J. Fracture corridors as seal-bypass systems in siliciclastic reservoir-cap rock successions: Field-based insights from the Jurassic Entrada Formation (SE Utah, USA). J. Struct. Geol. 2014, 66, 162–187. [Google Scholar] [CrossRef]
- Shukla, R.; Ranjith, P.G.; Choi, S.K.; Haque, A.; Yellishetty, M.; Hong, L. Mechanical behaviour of reservoir rock under brine saturation. Rock Mech. Rock Eng. 2013, 46, 83–93. [Google Scholar] [CrossRef]
- Ingram, G.M.; Urai, J.L. Top-seal leakage through faults and fractures: The role of mudrock properties. Geol. Soc. Lond. Spec. Publ. 1999, 158, 125–135. [Google Scholar] [CrossRef]
- Swansson, S.R.; Brown, W.S. An observation of loading path independence of fracture in rock. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 1971, 8, 277–281. [Google Scholar] [CrossRef]
- Shimamoto, T. Confining pressure reduction experiments: A new method for measuring frictional strength over a wide range of normal stress. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 1985, 22, 227–236. [Google Scholar] [CrossRef]
- Viktorov, S.D.; Kochanov, A.N. Investigation into the processes of rock sample unloading after blast loading. J. Min. Sci. 2004, 40, 160–164. [Google Scholar] [CrossRef]
- Lau, J.S.O.; Chandler, N.A. Innovative laboratory testing. Int. J. Rock Mech. Min. Sci. 2004, 41, 1427–1445. [Google Scholar] [CrossRef]
- Huang, R.Q.; Huang, D. Experimental research on affection laws of unloading rates on mechanical properties of Jinping marble under high geostress. Chin. J. Rock Mech. Eng. 2010, 29, 21–33. (In Chinese) [Google Scholar]
- Huang, X.; Liu, Q.S.; Liu, B.; Liu, X.W.; Pan, Y.C.; Liu, J.P. Experimental study on the dilatancy and fracturing behavior of soft rock under unloading conditions. Int. J. Civ. Struct. Eng. 2017, 15, 1–28. [Google Scholar] [CrossRef]
- Zhang, L.M.; Wang, Z.Q.; Shi, L. Experimental study of hard rock failure characteristic under unloading condition. Chin. J. Rock Mech. Eng. 2011, 30, 1230–1236. (In Chinese) [Google Scholar] [CrossRef]
- Lv, Y.H.; Liu, Q.S.; Jiang, H. Study of mechanical deformation characteristics of granite in unloading experiments of high stress. Rock Soil Mech. 2010, 31, 337–344. (In Chinese) [Google Scholar] [CrossRef]
- Wu, F.Q.; Liu, J.Y.; Liu, T.; Zhuang, H.Z.; Yan, C.G. A method for assessment of excavation damaged zone (EDZ) of a rock mass and its application to a dam foundation case. Eng. Geol. 2009, 104, 254–262. [Google Scholar] [CrossRef]
- He, M.C.; Miao, J.L.; Feng, J.L. Rock burst process of limestone and its acoustic emission characteristics under true-triaxial unloading conditions. Int. J. Rock Mech. Min. Sci. 2010, 47, 286–298. [Google Scholar] [CrossRef]
- Hatheway, A.W. The complete ISRM suggested methods for rock characterization, testing, and monitoring: 1974–2006. Environ. Eng. Geol. 2009, 15, 47–48. [Google Scholar] [CrossRef]
- Hou, Z.K.; Yang, C.H.; Wei, X.; Wang, L.; Wei, Y.L.; Xu, F.; Wang, H. Experimental study on the brittle characteristics of Longmaxi formation shale. J. China Coal Soc. 2016, 41, 1188–1196. (In Chinese) [Google Scholar] [CrossRef]
- Hou, Z.K.; Yang, C.H.; Wang, L.; Xu, F. Evaluation Method of Shale Brittleness Based on Indoor Experiments. J. Northeast. Univ. Nat. Sci. 2016, 37, 1496–1501. (In Chinese) [Google Scholar] [CrossRef]
- Altindag, R. The evaluation of rock brittleness concept on rotary blast hold drills. J. S. Afr. Inst. Min. Metall. 2002, 102, 61–66. [Google Scholar]
- Hucka, V.; Das, B. Brittleness determination of rocks by different methods. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 1974, 11, 389–392. [Google Scholar] [CrossRef]
- Honda, H.; Sanada, Y. Hardness of coal. Fuel 1956, 35, 451–461. [Google Scholar]
- Quinn, J.B.; Quinn, D.G. Indentation brittleness of ceramics: A fresh approach. J. Mater. Sci. 1997, 32, 4331–4346. [Google Scholar] [CrossRef]
- Lawn, B.; Marshall, D. Hardness, toughness, and brittleness: An indentation analysis. J. Am. Ceram. Soc. 1979, 62, 347–350. [Google Scholar] [CrossRef]
- Azant, Z.P.; Kazemi, M.T. Determination of fracture energy, process zone length and brittleness number from size effect, with application to rock and concrete. Int. J. Fract. 1990, 44, 111–131. [Google Scholar] [CrossRef]
- Hajiabdolmajid, V.; Kaiser, P. Brittleness of rock and stability assessment in hard rock tunneling. Tunn. Undergr. Space Eng. 2003, 18, 35–48. [Google Scholar] [CrossRef]
- Copur, H. Theoretical and Experimental Studies of Rock Cutting with Drag Bits Toward the Development of a Performance Prediction Model for Roadheaders. Ph.D Thesis, Colorado School of Mines, Golden, CO, USA, 1999. [Google Scholar]
- Yagiz, S. An investigation on the relationship between rock strength and brittleness. In Proceedings of the 59th Geological Congress of Turkey, Ankara, Turkey, 20–24 March 2006; MTA General Directory Press: Ankara, Turkey, 2006. [Google Scholar]
- Blindheim, O.T.; Bruland, A. Boreability testing. Nor. TBM Tunn. 1998, 30, 29–34. [Google Scholar]
- Protodyakonov, M.M. Mechanical properties and drillability of rocks. In Proceedings of the 5th Symposium Rock Mechanics, University of Minnesota, Minneapolis, MN, USA, May 1962. [Google Scholar]
- Rickman, R.; Mullen, M.J.; Petre, J.E.; Grieser, W.V.; Kundert, D. A practical use of shale petrophysics for stimulation design optimization: All shale plays are not clones of the Barnett Shale. In Proceedings of the SPE Annual Technical Conference and Exhibition, Denver, CO, USA, 21–24 September 2008; Society of Petroleum Engineers: Denver, CO, USA, 2008. [Google Scholar]
- 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]
- Heng, S.; Yang, C.H.; Li, Z.; Wang, L.; Hou, Z.K. Shale brittleness estimation based on energy dissipation. J. Cent. South Univ. Nat. Sci. 2016, 47, 577–585. (In Chinese) [Google Scholar] [CrossRef]
- Li, Q.H.; Chen, M.; Jin, Y.; Wang, F.P.; Hou, B.; Zhang, B.W. Indoor evaluation method for shale brittleness and improvement. Chin. J. Rock Mech. Eng. 2012, 31, 1680–1685. (In Chinese) [Google Scholar]
- Aubertin, M.; Gill, D.E.; Simon, R. On the use of the brittleness index modified (BIM) to estimate the post-peak behavior of rocks. In Proceedings of the 1st North American Rock Mechanics Symposium, Austin, TX, USA, 1–3 June 1994; American Rock Mechanics Association: Austin, TX, USA, 1994. [Google Scholar]
- Feng, T.; Xie, X.B.; Wang, W.X.; Pan, C.L. Brittleness of rock and brittleness coefficient describing rockburst tendency. Min. Metall. Eng. 2000, 20, 18–19. (In Chinese) [Google Scholar]
- George, E.A. Brittle failure of rock material-test results and constitutive models. AA Balkema/Rotterdam/Brolkfield 1995, 2, 123–128. [Google Scholar] [CrossRef]
- Bishop, A.W. Progressive failure with special reference to the mechanism causing it. Proc. Geotech. Conf. Oslo 1967, 2, 142–150. [Google Scholar]
- Stavrogin, A.N.; Tarasov, B.G. Experimental Physics and Rock Mechanics; CRC Press: Boca Raton, FL, USA, 2001. [Google Scholar]
- Zhou, H.; Meng, F.Z.; Zhang, C.Q.; Xu, R.C.; Lu, J.J. Quantitative evaluation of rock brittleness based on stress–strain curve. Chin. J. Rock Mech. Eng. 2014, 33, 1114–1122. (In Chinese) [Google Scholar] [CrossRef]
Serial Number | Density g/cm3 | ε1 | ε2 | ε3 | σ3 (MPa) | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
RF-1-15 | 2.54 | 1.78 | 0.22 | 1.33 | 60 | 0.05 | −1.3 | 229.73 | 2.36 | 165.86 | 2.22 | 54.27 | 1.74 |
RF-4-11 | 2.51 | 1.70 | 0.27 | 1.16 | 60 | 0.05 | −1.3 | 239.61 | 2.38 | 151.70 | 2.18 | 44.39 | 1.65 |
RF-2-6 | 2.52 | 1.68 | 0.30 | 1.07 | 60 | 0.1 | −1 | 233.42 | 2.39 | 148.08 | 2.17 | 50.79 | 1.71 |
RF-3-3 | 2.52 | 1.86 | 0.38 | 1.11 | 60 | 0.1 | −1 | 239.82 | 2.38 | 145.49 | 2.16 | 44.92 | 1.65 |
RF-4-2 | 2.52 | 1.74 | 0.27 | 1.19 | 60 | 0.1 | −1 | 238.48 | 2.38 | 174.39 | 2.24 | 46.11 | 1.66 |
RF-2-5 | 2.52 | 1.64 | 0.36 | 0.92 | 60 | 0.5 | −0.3 | 241.51 | 2.38 | 137.32 | 2.14 | 43.09 | 1.63 |
RF-3-4 | 2.53 | 1.62 | 0.40 | 0.81 | 60 | 0.5 | −0.3 | 240.82 | 2.38 | 151.60 | 2.18 | 43.57 | 1.64 |
RF-3-5 | 2.53 | 1.69 | 0.34 | 1.02 | 60 | 0.5 | −0.3 | 246.22 | 2.39 | 132.95 | 2.12 | 38.64 | 1.59 |
RF-2-2 | 2.52 | 1.95 | 0.45 | 1.05 | 60 | 1.0 | 0 | 252.00 | 2.40 | 142.00 | 2.15 | 32.76 | 1.52 |
RF-2-9 | 2.52 | 1.73 | 0.28 | 1.17 | 60 | 1.0 | 0 | 249.63 | 2.40 | 132.95 | 2.12 | 35.11 | 1.55 |
RF-4-5 | 2.53 | 1.83 | 0.51 | 0.82 | 60 | 1.0 | 0 | 247.88 | 2.40 | 125.00 | 2.10 | 36.69 | 1.57 |
Method | Equation | Description | Resource |
---|---|---|---|
Pressing ratio | Mean of the product of uniaxial compressive strength and tensile strength . | Altindag [29] | |
Pressing ratio | The function of uniaxial compression and tensile strength ratio. | Altindag [29] | |
Pressing ratio | The ratio of uniaxial compressive strength to tensile strength . | Hucka and Das [30] | |
Pressing ratio | The function of uniaxial compression and tensile strength ratio. | Hucka and Das [30] | |
Hardness test | is the macro hardness and is the micro hardness. | Honda and Sanada [31] | |
Hardness, fracture test | is a hardness coefficient, is Young’s modulus, and is the fracture toughness. | J. B. Quinn and G. D. Quinn [32] | |
Hardness, fracture test | is a hardness coefficient, is Young’s modulus, and is the fracture toughness. | Lawn and Marshall [33] | |
Hardness test | is the fracture toughness, is the yield stress, and is the characteristic size of the sample. | Bazant and Kazemi [34] | |
Bazant curve | The ratio of elastic energy to fracture energy, is the fracture energy, is elastic modulus, and is Hllebrgorg characteristic length value. | Bazant and Kazemi [34] | |
Cohesion-weakening-friction-strengthening (CWFS) model | and is the plastic strain when the friction strength and cohesive force reaches the final limit value, respectively. | Hajiabdolmajid et al. [35] | |
Penetration test | The ratio of incremental load to decay load. | Copur [36] | |
Penetration test | The ratio of the maximum impact load to the penetration depth. | Yagiz [37] | |
Impact test | Percentage of fine debris less than 11.2 mm in diameter. | Blindheim and Bruland [38] | |
Impact test | is the percentage that less than 0.6 mm of debris and is uniaxial compressive strength. | Protodyakonov [39] | |
Mohr stress circle | Sinusoidal value of internal friction angle. | Hucka and Das [30] | |
Mohr stress circle | The function of the internal friction angle. | Hucka and Das [30] | |
Mineral composition analysis | The ratio of brittle mineral content to total mineral content. | Rickman et al. [40] | |
Mineral composition analysis | The ratio of quartz to total mineral content. | Jarvie [41] | |
Energy dissipation, stress–strain curve | The ratio of rupture energy per unit volume consumption to elastic energy released internally. | Heng et al. [42] | |
Stress–strain curve | The sum of the peak strain index and the post-peak curve shape index. | Li et al. [43] | |
Stress–strain curve | The ratio of recoverable strain energy to total energy. | Hucka and Das [30] | |
Stress–strain curve | is the area under the oblique line of the peak intensity point with the deformation modulus as the slope and is the area under the loading curve. | Aubertin et al. [44] | |
Stress–strain curve | is uniaxial compressive strength, is tensile strength, and is a pre-peak and a post-peak strain, respectively, and is adjustment parameter. | Feng et al. [45] | |
Stress–strain curve | is an unrecoverable axial strain when the specimen is broken, it is brittle when < 3%, brittle plasticity when at 3%–5%, and plasticity when > 5%. | George [46] | |
Stress–strain curve | The ratio of normalization of elastic modulus and Poisson. | Rickman et al. [40] | |
Stress–strain curve | The ratio of recoverable strain to total strain . | Hucka and Das [30] | |
Stress–strain curve, Fracture test | The ratio of elastic energy to fracture energy, is the fracture energy, is elastic modulus, and is characteristic length value. | Bazant and Kazem [34] | |
Stress–strain curve | is the peak strength and is the residual strength. | Bishop [47] | |
Stress–strain curve | The function of is peak strain and residual strain . | Ajiabdolmajid and Kaiser [35] | |
Stress–strain curve | The ratio of fracture damage energy to pre-peak elastic strain energy after rock rupture peak. | Stavrogin and Tarasov [48] | |
Stress–strain curve | is the peak strength, is the residual strength, and is the slope of different peak intensity points to the drop point, respectively. | Zhou et al. [49] | |
Stress–strain curve | is the peak strength, is the residual strength, , , and are the axial strain and . | Hou et al. [27] | |
Stress–strain curve | is the peak strength, is the residual strength, and , , and is the axial strain. | Hou et al. [27] |
Confining Pressure | 0 | 20 | 40 | 60 | 80 | |
---|---|---|---|---|---|---|
Parameters | ||||||
0.76 | 1.21 | 1.71 | 1.86 | 2.37 | ||
0.76 | 1.16 | 1.53 | 1.72 | 1.91 | ||
11.10 | 16.09 | 17.38 | 18.82 | 18.83 | ||
35.58 | 106.18 | 149.83 | 196.79 | 216.49 | ||
0.00 | 20.00 | 40.00 | 60.00 | 80.00 | ||
0.24 | 0.18 | 0.17 | 0.21 | 0.23 | ||
90.58 | 162.42 | 239.33 | 280.45 | 306.60 | ||
−1375.00 | −117.17 | −52.34 | −60.63 | −19.34 | ||
1.00 | 1.01 | 1.02 | 1.01 | 1.04 | ||
0.61 | 0.35 | 0.37 | 0.30 | 0.29 | ||
1.00 | 1.00 | 0.95 | 0.96 | 0.64 | ||
0.87 | 0.78 | 0.78 | 0.76 | 0.66 | ||
0.61 | 0.35 | 0.36 | 0.29 | 0.20 |
No. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Parameters | ||||||||||||
230.26 | 240.44 | 233.42 | 239.82 | 238.61 | 241.51 | 240.82 | 246.22 | 252.00 | 249.63 | 247.88 | ||
160.10 | 113.15 | 91.95 | 133.20 | 111.36 | 144.95 | 116.54 | 120.80 | 142.00 | 137.48 | 122.59 | ||
160.10 | 113.15 | 91.95 | 133.20 | 111.36 | 144.95 | 116.54 | 120.80 | 142.00 | 137.48 | 122.59 | ||
1.57 | 1.45 | 1.51 | 1.54 | 1.57 | 1.45 | 1.47 | 1.46 | 1.67 | 1.51 | 1.57 | ||
2.27 | 2.46 | 2.19 | 2.22 | 1.99 | 2.27 | 2.23 | 2.03 | 2.48 | 2.30 | 2.33 | ||
1.01 | 0.65 | 0.55 | 0.74 | 0.69 | 0.79 | 0.71 | 0.71 | 0.81 | 0.77 | 0.77 | ||
17.81 | 17.74 | 18.44 | 18.28 | 16.69 | 18.52 | 17.56 | 18.07 | 17.35 | 18.16 | 17.03 | ||
0.21 | 0.27 | 0.29 | 0.26 | 0.27 | 0.32 | 0.26 | 0.25 | 0.24 | 0.23 | 0.25 | ||
−10.02 | −12.60 | −20.80 | −15.68 | −30.30 | −11.78 | −16.35 | −22.00 | −13.58 | −14.20 | −16.49 | ||
1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | ||
0.30 | 0.53 | 0.61 | 0.44 | 0.53 | 0.40 | 0.52 | 0.51 | 0.44 | 0.45 | 0.51 | ||
0.43 | 0.51 | 0.68 | 0.58 | 0.84 | 0.47 | 0.61 | 0.70 | 0.54 | 0.54 | 0.62 | ||
0.58 | 0.68 | 0.76 | 0.67 | 0.79 | 0.62 | 0.71 | 0.74 | 0.66 | 0.66 | 0.71 | ||
0.13 | 0.27 | 0.41 | 0.26 | 0.45 | 0.19 | 0.31 | 0.36 | 0.24 | 0.24 | 0.31 |
No. | 1-15 | 4-11 | 2-7 | 3-3 | 4-2 | 2-5 | 3-4 | 3-5 | 2-2 | 2-9 | 4-5 |
---|---|---|---|---|---|---|---|---|---|---|---|
/GPa | 15.74 | 38.73 | 22.59 | 26.50 | 41.25 | 44.90 | 58.40 | 50.50 | 42.68 | 65.38 | 52.60 |
No. | 1-15 | 4-11 | 2-7 | 3-3 | 4-2 | 2-5 | 3-4 | 3-5 | 2-2 | 2-9 | 4-5 |
---|---|---|---|---|---|---|---|---|---|---|---|
/GPa | 16.57 | 30.33 | 20.93 | 23.21 | 31.43 | 34.35 | 42.06 | 37.53 | 32.55 | 46.49 | 38.37 |
No. | 1-15 | 4-11 | 2-7 | 3-3 | 4-2 | 2-5 | 3-4 | 3-5 | 2-2 | 2-9 | 4-5 |
---|---|---|---|---|---|---|---|---|---|---|---|
0.688 | 0.950 | 0.893 | 0.789 | 0.846 | 0.836 | 0.993 | 0.880 | 0.842 | 0.947 | 0.937 | |
0.326 | 0.725 | 0.716 | 0.504 | 0.617 | 0.508 | 0.759 | 0.637 | 0.545 | 0.649 | 0.692 |
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Zhou, X.; Liu, H.; Guo, Y.; Wang, L.; Hou, Z.; Deng, P. An Evaluation Method of Brittleness Characteristics of Shale Based on the Unloading Experiment. Energies 2019, 12, 1779. https://doi.org/10.3390/en12091779
Zhou X, Liu H, Guo Y, Wang L, Hou Z, Deng P. An Evaluation Method of Brittleness Characteristics of Shale Based on the Unloading Experiment. Energies. 2019; 12(9):1779. https://doi.org/10.3390/en12091779
Chicago/Turabian StyleZhou, Xiaogui, Haiming Liu, Yintong Guo, Lei Wang, Zhenkun Hou, and Peng Deng. 2019. "An Evaluation Method of Brittleness Characteristics of Shale Based on the Unloading Experiment" Energies 12, no. 9: 1779. https://doi.org/10.3390/en12091779