Damage Characteristics Analysis and Fractal Study of Shale With Prefabricated Fractures under Thermal-mechanical Coupling

Abstract

To study the damage and failure of shale with different fracture inclination angles under uniaxial compression loading, in this work, RFPA2D-Thermal, a two-dimensional real failure process analysis software, was used for numerical simulation. Numerical simulation results show that quartz in shale mainly affects the tensile and compressive strength of shale by increasing rock brittleness. The coupling of temperature and pressure will cause lateral and volume destruction of shale, which enables the shale body to be more easily broken. Fracture inclination is the key factor affecting shale damage patterns. The failure mode of shale with low- and high-angle fractures is mainly shear failure, and the compressive strength does not vary with crack inclination. The damage mode of obliquely intersecting fractured shale is slip damage along the fracture face, the compressive strength decreases and then increases with the fracture inclination, and a minimum value exists. The acoustic emission simulation results of the damage process effectively reflect the accumulated internal damage and macroscopic crack appearance until fracture instability when the prefabricated fractured shale is subjected to uniaxial compressive loading. The crack inclinations of 0° and 120 °C corresponds to the most complex “N” shape damage mode. The crack inclinations of 30° and 60°, and the damage mode is an inverted “λ” shape.

Keywords

shale / temperature and pressure / numerical simulation / fracture dip angle / fractal dimension

References

[1] Mu HM, Wan YY, Wu BC, et al. A Rapid Change in Microbial Communities of the Shale Gas Drilling Fluid from 3 548 m Depth to the Above-Ground Storage Tank[J]. Sci. Total Environ., 2021, 784: 147 009.

[2] Gao K, Guo GJ, Zhang M, et al. Nanopore Surfaces Control the Shale Gas Adsorption Via Roughness and Layer-Accumulated Adsorption Potential: A Molecular Dynamics Study[J]. Energ. Fuel, 2021, 35(6): 4 893-4 900.

[3] Peng S, Zhang Y, Zhao W, et al. Analysis of the Influence of Rectifier Blockage on the Metering Performance During Shale Gas Extraction[J]. Energ. Fuel, 2021, 35: 3 748.

[4] Ji A, Lxa B, Bo HA, et al. Influence of Anisotropic and Heterogeneous Permeability Coupled with In-Situ Stress on CO₂ Sequestration with Simultaneous Enhanced Gas Recovery in Shale: Quantitative Modeling and Case Study[J]. Int. J. Greenh Gas Con., 2021, 103 208

[5] Vengosh A, Jackson RB, Warner N, et al. A Critical Review of the Risks to Water Resources from Unconventional Shale Gas Development and Hydraulic Fracturing in the United States[J]. Environ. Sci. Technol., 2014, 48: 8 334-8 348.

[6] Ge X, Guo T, Ma Y, et al. Fracture Development and Inter-Well Interference for Shale Gas Production From the Wufeng-Longmaxi Formation in a Gentle Syncline Area of Weirong Shale Gas Field, Southern Sichuan, China[J]. Journal of Petroleum Science and Engineering, 2022, 212: 110 207.

[7] Li JL, Zhang TS, Li YJ, et al. Geochemical Characteristics and Genetic Mechanism of the High-N₂ Shale Gas Reservoir in the Longmaxi Formation, Dianqianbei Area, China[J]. Petrol Sci., 2020, 17: 939-953.

[8] Peng J, Milliken KL. Grain Assemblages and Diagenesis in Organic-Rich Mudrocks, Upper Pennsylvanian Cline Shale (Wolfcamp D), Midland Basin, Texas[J]. Aapg. Bull., 2020, 104(7): 1 593-1 624.

[9] Taylor Macquaker. Diagenetic Alterations in a Silt and Clay-Rich Mudstone Succession: an Example from the Upper Cretaceous Mancos Shale of Utah, USA[J]. Clay Miner., 2014, 49(2): 213-227.

[10] Sun C, Nie H, Liu G, et al. Quartz Type and Its Control on Shale Gas Enrichment and Production:A Case Study of the Wufeng-Longmaxi Formations in the Sichuan Basin and Its Surrounding Areas, China[J]. Earth Science, 2019, 44(2): 513-523.

[11] Zhang B, Yan D, Drawarh HJ, et al. Formation Mechanism and Numerical Model of Quartz in Fine-Grained Organic-Rich Shales: A Case Study of Wufeng and Longmaxi Formations in Western Hubei Province, South China[J]. Journal of Earth Sci., 2020, 31: 354-367.

[12] Jlabc D, Wdabc D, Rw E, et al. Quartz Types in Shale and Their Effect on Geomechanical Properties: An Example From the Lower Cambrian Niutitang Formation in the Cen’gong Block, South China - Science Direct[J]. Appl. Clay Sci., 2018, 163: 100-107.

[13] Zhang Z, Kong X, Chen Q, et al. Quantitative Characterization and Determination of the Main Factors That Control Fracture Development in the Lower Paleozoic Shale in Southeastern Chongqing, China[J]. Geofluids, 2021: 1–11

[14] Zhu H, Ju Y, Yang M, et al. Grain-Scale Petrographic Evidence for Distinguishing Detrital and Authigenic Quartz in Shale: How Much of a Role Do They Play for Reservoir Property and Mechanical Characteristic[J]. Energy, 2022, 12: 21-76.

[15] Wu Z, Song H, Li L, et al. Study on the Damage Evolution Process and Fractal of Quartz-Filled Shale under Thermal-Mechanical Coupling[J]. Geofluids, 2021: 1–14

[16] Peng J, Milliken KL, Fu Q. Quartz Types in the Upper Pennsylvanian Organic-Rich Cline Shale (Wolfcamp D), Midland Basin, Texas: Implications for Silica Diagenesis, Porosity Evolution and Rock Mechanical Properties[J]. Sedimentology, 2020, 12: 87-94.

[17] Chattopadhyay B, Madathiparambil AS, Mürer FK, et al. Nanoscale Imaging of Shale Fragments with Coherent X-ray Diffraction[J]. J. Appl. Crystallogr., 2020, 53: 1 562-1 569.

[18] He W, Sun Y, Shan X. Organic Matter Evolution in Pyrolysis Experiments of Oil Shale Under High Pressure: Guidance for in Situ Conversion of Oil Shale in the Song liao Basin[J]. J. Anal. Appl. Pyrol., 2021, 155: 105 091.

[19] Stian R, Andreas B, Holt RM. On the Low-Frequency Elastic Response of Pierre Shale During Temperature Cycles[J]. Geophys. J. Int., 2021, 2: 1 260-1 280.

[20] Lingdong L, Xiaoning Z, Ruiqing M, et al. Mechanical Properties of Shale Under the Coupling Effect of Temperature and Confining Pressure[J]. Chem. Tech. Fuels Oil., 2021, 57: 841-846.

[21] Yang S, Yang D, Kang Z. Experimental Investigation of the Anisotropic Evolution of Tensile Strength of Oil Shale Under Real-Time High-Temperature Conditions[J]. Nat. Resour. Res., 2021, 30: 2 513-2 528.

[22] Lei W, Dong Y, Zka B. Evolution of Permeability and Mesostructure of Oil Shale Exposed to High-Temperature Water Vapor[J]. Fuel, 2020, 119 786

[23] Li Z, Duan Y, Peng Y, et al. A Laboratory Study of Microcracks Variations in Shale Induced by Temperature Change[J]. Fuel, 2020, 280: 118 636.

[24] Masri M, Sibai M, Shao JF, et al. Experimental Investigation of the Effect of Temperature on the Mechanical Behavior of Tournemire Shale[J]. International Journal of Rock Mechanics & Mining Sciences, 2014, 70: 185-191.

[25] Johnston DH. Physical Properties of Shale at Temperature and Pressure[J]. Geophysics, 1987, 52(10): 1 391-1 401.

[26] Zhao J, Zhang D. Dynamic Microscale Crack Propagation in Shale[J]. Eng. Fract. Mech., 2020, 228: 106 906.

[27] Dou F, Wang JG, Leung CF, et al. The Alterations of Critical Pore Water Pressure and Micro-Cracking Morphology with Near-Wellbore Fractures in Hydraulic Fracturing of Shale Reservoirs[J]. Eng. Fract. Mech., 2020, 242: 107 481.

[28] Vega B, Yang J, Tchelepi H, et al. Investigation of Stress Field and Fracture Development During Shale Maturation Using Analog Rock Systems[J]. Transport Porous Med., 2020, 131: 503-535.

[29] Nguyen-Le DH, Tao QB, Nguyen VH, et al. A Data-Driven Approach Based on Long Short-Term Memory and Hidden Markov Model for Crack Propagation Prediction[J]. Eng. Fract. Mech., 2020, 235: 107 085.

[30] Hui W, Li Y, Cao S, et al. Fracture Toughness Analysis of HCCD Specimens of Longmaxi Shale Subjected to Mixed Mode I–II Loading[J]. Eng. Fract. Mech., 2020, 23: 18-25.

[31] Liu J, Xue Y, Zhang Q, et al. Micro-Cracking Behavior of Shale Matrix During Thermal Recovery: Insights From Phase-Field Modeling[J]. Eng. Fract. Mech., 2020, 23: 89-97.

[32] Sakhaee-Pour A, Li W. Fractal Dimensions of Shale[J]. J. Nat. Gas Sci. Eng., 2016, 2016: 578-582.

[33] Lina HU, Zhu Y, Chen S, et al. Fractal Characteristics of Shale Pore Structure of Longmaxi Formation in Shuanghe Area in Southern Sichuan[J]. Xinjiang Petroleum Geology, 2013, 171: 52-59.

[34] Hammersley JM. Simulation and the Monte Carlo Method[J]. B Lond Math Soc., 1981, 392: 35-48.

[35] Wang R, Zongquan HU, Nie H, et al. Comparative Analysis and Discussion of Shale Reservoir Characteristics in the Wufeng-Longmaxi and Niutitang Formations: a Case Study of the Well JY1 in SE Sichuan Basin and Well TX1 in SE Guizhou Area[J]. Petroleum Geology & Experiment, 2018, 40(5): 639-649.

[36] Cui H, Wu Z, Li L, et al. Numerical Test Study of the Microscale Failure Modes and Fractal Analysis of Lower Cambrian Shale Based on Digital Images[J]. Adv. Civ. Eng., 2020, 2020: 1-16.

[37] Nie H, Tang X, Bian R. Controlling Factors for Shale Gas Accumulation and Prediction of Potential Development Area in Shale Gas Reservoir of South China[J]. Acta Petrolei Sinica, 2009, 30(4): 8-17.

[38] Qin S, Liu A. A Discussion on the Himalayan Tectonic Movement in Guizhou[J]. Guizhou Geology, 1998, 15(2): 105-114.

[39] Zhu W, Wei C, Tian J, et al. Coupled Thermal-Hydraulic-Mechanical Model During Rock Damage and Its Preliminary Application[J]. Rock and Soil Mechanics, 2016, 30(12): 3 851-3 857.

[40] Wei CH, Zhu WC, Yu QL, et al. Numerical Simulation of Excavation Damaged Zone Under Coupled Thermal-Mechanical Conditions with Varying Mechanical Parameters[J]. International Journal of Rock Mechanics & Mining Sciences, 2015, 75: 169-181.

[41] Gao F, Xue Y, Gao Y, et al. Fully Coupled Thermo-Hydro-Mechanical Model for Extraction of Coal Seam Gas With Slotted Boreholes[J]. Journal of Natural Gas Science & Engineering, 2016, 31: 226-235.

[42] Sya B, Rx C, Zw D, et al. In Situ. Mar. Petrol Geol., 2019, 99: 75-91.

[43] Zhang L, Sun M, Lv Q, et al. Evolution of Shale Microstructure under in situ Heat Treatment: Synchrotron Small-Angle X-ray Scattering[J]. Energ. Fuel, 2021, 35: 4 345-4 357.

[44] Zhang S W, Shou K J, Xian X, et al. Fractal Characteristics and Acoustic Emission of Anisotropic Shale in Brazilian Tests[J]. Tunn. Undergr Sp Tech., 2018, 71: 298-308.

[45] Gkza B, Hbla C, Myw B, et al. Crack Initiation of Granite Under Uniaxial Compression Tests: A Comparison Study - Science Direct[J]. Journal of Rock Mechanics and Geotechnical Engineering, 2020, 12: 656-666.

[46] Ni K, Yang J, Ning Y, et al. A Modified Sub-Block DDA Fracturing Modelling Method for Rock[J]. Eng. Anal. Bound Elem., 2020, 111: 154-166.

[47] Wu Z, Zuo Y, Wang S, et al. Numerical Study of Multi-Period Palaeotectonic Stress Fields in Lower Cambrian Shale Reservoirs and the Prediction of Fractures Distribution: A Case Study of the Niutitang Formation in Feng’gang No. 3 block, South China[J]. Mar Petrol Geol., 2017, 80: 369-381.

[48] Zhang L. Estimating the Strength of Jointed Rock Masses[J]. Rock Mechanics & Rock Engineering, 2010, 43: 391-402.

[49] Tang CA, Xu XH. Evolution and Propagation of Material Defects and Kaiser Effect Function[J]. Journal of Seismological Research, 1990, 02: 203-213.