The effect of fracture growth rate on fracture process zone development in quasi-brittle rock

Chen, Lei; Zhang, Guangqing; Zou, Zhikun; Guo, Yuanzhe; Zheng, Xiaowei

doi:10.1016/j.engfracmech.2021.108086

Cited by 24 publications

(12 citation statements)

References 37 publications

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“…The fracture experiment conducted by Kong et al [166] using granite shows that the FPZ width remains approximately unchanged. The experiments carried out by Chen et al [167] with sandstone show that the length and width of the FPZ remain approximately unchanged. However, the FPZ width is slightly less than the length.…”

Section: Fracture Process Zonementioning

confidence: 96%

“…It is found that the FPZ width also increases with the fracture propagation speed [144]. Chen et al [178] found that the FPZ not only increases with the increase in the fracture propagation speed, but also develops from semi-elliptic to strip type. This can also explain that the rock fracture toughness increases with the increase in the loading rate [179].…”

Section: Fracture Process Zonementioning

confidence: 98%

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A Review of the Hydraulic Fracturing in Ductile Reservoirs: Theory, Simulation, and Experiment

Zhu

Han

et al. 2022

Processes

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The bottom-hole pressure of hydraulic fracturing in ductile reservoirs is much higher than that of the hydraulic fracturing simulation, and the fracture toughness inferred from the field data is 1–3 orders of magnitude higher than that measured in the laboratory. The rock apparent fracture toughness increases with the increase in the confining pressure. Excluding the influence of the fluid viscosity and the fluid lag on the apparent fracture toughness, the fracture process zone (FPZ) at the fracture tip can explain the orders of magnitude of difference in the apparent fracture toughness between the laboratory and the field. The fracture tip is passivated by plastic deformation, forming a wide and short hydraulic fracture. However, the size of the FPZ obtained in the laboratory is in the order of centimeters to decimeters, while an FPZ of 10 m magnitude is speculated in the field. The FPZ size is affected by the rock property, grain size, pore fluid, temperature, loading rate, and loading configuration. It is found that the FPZ has a size effect that tends to disappear when the rock specimen size reaches the scale of meters. However, this cannot fully explain the experience of hydraulic fracturing practice. The hydraulic fracturing behavior is also affected by the relation between the fracture toughness and the fracture length. The fracture behavior of type II and mixed type for the ductile rock is poorly understood. At present, the apparent fracture toughness model and the cohesive zone model (CZM) are the most suitable criteria for the fracture propagation in ductile reservoirs, but they cannot fully characterize the influence of the rock plastic deformation on the hydraulic fracturing. The elastic-plastic constitutive model needs to be used to characterize the stress–strain behavior in the hydraulic fracturing simulation, and the fracture propagation criteria suitable for ductile reservoirs also need to be developed.

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Section: Fracture Process Zonementioning

confidence: 96%

Section: Fracture Process Zonementioning

confidence: 98%

A Review of the Hydraulic Fracturing in Ductile Reservoirs: Theory, Simulation, and Experiment

Zhu

Han

et al. 2022

Processes

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“…Scholars have conducted numerous studies on the main control factors affecting fracture propagation in fractured shale reservoirs using physical simulation experiments and numerical simulations. In general, the main controlling factors of fracture propagation in shale reservoirs [2,14,17,28,30,56,121,122] can be divided into two categories: geological factors and engineering factors. Among them, geological factors are caused by the nature of the shale reservoir itself, mainly the mineral composition of the shale, rock mechanical parameters, natural fractures, laminar surfaces, fracture interaction, and crustal stress [22,31,38,82,120,123,124].…”

Section: The Main Control Factor Of Fracture Propagation In Shale Res...mentioning

confidence: 99%

Advances in Hydraulic Fracture Propagation Research in Shale Reservoirs

Gong

Liu

et al. 2022

Minerals

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The characterization of artificial fracture propagation law in the fracturing process of shale reservoirs is the basis for evaluating the fracture conductivity and a key indicator of the reservoir stimulated effect. In order to improve the fracture stimulated volume of shale reservoirs, this paper systematically discusses the current status of research on artificial fracture propagation law from the research methods and main control factors and provides an outlook on its future development direction. The analysis finds that the study of fracture propagation law by using indoor physical simulation experiments has the advantages of simple operation and intuitive image, and the introduction of auxiliary technologies such as acoustic emission monitoring and CT scanning into indoor physical model experiments can correct the experimental results so as to better reveal the propagation mechanism of artificial fractures. At present, the numerical simulation methods commonly used to study the propagation law of artificial fractures include the finite element method, extended finite element method, discrete element method, boundary element method and phase field method, etc. The models established based on these numerical simulation methods have their own advantages and applicability, so the numerical algorithms can be integrated and the numerical methods selected to model and solve the different characteristics of the propagation law of artificial fractures in different regions at different times can greatly improve the accuracy of the model solution and better characterize the propagation law of artificial fractures. The propagation law of artificial fracture in the fracturing process is mainly influenced by geological factors and engineering factors, so when conducting research, geological factors should be taken as the basis, and through detailed study of geological factors, the selection of the fracturing process can be guided and engineering influencing factors can be optimized.

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“…For further validation of the proposed model, comparisons between experimental results of the Dagangshan diabase and the numerical simulations are carried out in this subsection. The experimental data are provided by an earlier work [48]. Now, we will provide numerical simulations of standard triaxial compression tests conducted with confining pressures of p c = 10, 15, 20, 30, 50 MPa.…”

Section: Numerical Simulations For Dagangshan Diabasementioning

confidence: 99%

Experimental Investigation and Micromechanical Modeling of Hard Rock in Protective Seam Considering Damage–Friction Coupling Effect

et al. 2022

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The hard rock in the protective coal seam of the Pingdingshan Mine in China is a typical quasi-brittle material exhibiting complex mechanical characteristics. According to available research on the mechanical property, the inelastic deformation and development of damage are considered related with crack initiation and propagation, which are main causes of the material degradation. In the present study, an original experimental investigation on the rock sample of the Pingdingshan coal mine is firstly carried out to obtain the basic mechanical responses in a conventional triaxial compression test. Based on the homogenization method and thermodynamic theory, a damage–friction coupled model is proposed to simulate the non-linear mechanical behavior. In the framework of micromechanics, the hard rock in a protective coal seam is viewed as a heterogeneous material composed of a homogeneous solid matrix and a large number of randomly distributed microcracks, leading to a Representative Elementary Volume (REV), i.e., the matrix–cracks system. By the use of the Mori–Tanaka homogenization scheme, the effective elastic properties of cracked material are obtained within the framework of micromechanics. The expression of free energy on the characteristic unitary is derived by homogenization methods and the pairwise thermodynamic forces associated with the inelastic strain and damage variables. The local stress tensor is decomposed to hydrostatic and deviatoric parts, and the effective tangent stiffness tensor is derived by considering both the plastic yield law and a specific damage criterion. The associated generalized Coulomb friction criterion and damage criterion are introduced to describe the evolution of inelastic strain and damage, respectively. Prepeak and postpeak triaxial response analysis is carried out by coupled damage–friction analysis to obtain analytical expressions for rock strength and to clarify the basic characteristics of the damage resistance function. Finally, by the use of the returning mapping procedure, the proposed damage–friction constitutive model is applied to simulate the deformation of Pingdingshan hard rock in triaxial compression with respect to different confining pressures. It is observed that the numerical results are in good agreement with the experimental data, which can verify the accuracy and show the obvious advantages of the micromechanic-based model.

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The effect of fracture growth rate on fracture process zone development in quasi-brittle rock

Cited by 24 publications

References 37 publications

A Review of the Hydraulic Fracturing in Ductile Reservoirs: Theory, Simulation, and Experiment

A Review of the Hydraulic Fracturing in Ductile Reservoirs: Theory, Simulation, and Experiment

Advances in Hydraulic Fracture Propagation Research in Shale Reservoirs

Experimental Investigation and Micromechanical Modeling of Hard Rock in Protective Seam Considering Damage–Friction Coupling Effect

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