Short‐term failure mechanism triggered by hydraulic fracturing

Wang, Gang; Liu, Yixin; Xu, Jiang

doi:10.1002/ese3.535

Cited by 14 publications

(11 citation statements)

References 67 publications

(149 reference statements)

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“…Drilling cores without obvious fractures were selected and were cut into cubes with dimensions of approximately 100 × 100 × 100 mm. Young's modulus of the samples was 6.79 GPa, the Poisson ratio was 0.26, the uniaxial compressive strength was 81.04 MPa, and the density was 2.32 g/cm 3 . A picture of some of the sandstone samples is presented in Figure 1.…”

Section: Methodsmentioning

confidence: 99%

“…Hydromechanical coupling in rock masses is an important issue for many rock mechanics and hydrogeology applications [1][2][3][4][5][6][7]. In mining and civil engineering, the redistribution of the stress field during the excavation of tunnels and underground caverns leads to the initiation and propagation of cracks, which can cause dramatic changes in the permeability of a rock mass [8,9].…”

Section: Introductionmentioning

confidence: 99%

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Shear Behavior and Anisotropy Characteristics of the Fracture Morphology of Sandstone with Different Water Contents

Sun

Qin

et al. 2020

Geofluids

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Hydromechanical coupling in rock masses is an important issue for many rock mechanics and hydrogeology applications. The change of a water-bearing state will induce the fracture of the intact rocks and further accelerate the shear slip instability of the sheared surface. To investigate the weakening effect of water content on the mechanical properties of a rock mass, laboratory direct shear tests combined with three-dimensional analysis of sheared surfaces were carried out on sandstone samples with different water contents. The variogram parameters, sill and range, were applied to quantify the morphology of shear fracture surfaces, to reflect the shear failure process of the intact rock, and to provide a basis for resliding instability of jointed rock. It was determined that the sill represents the height of the fluctuation body in the fracture surface and the range represents the single fluctuation body and may reflect the frequency of fluctuations. The test results revealed that the increase in water content had a clear weakening effect on the shear strength and deformation behavior of rock, especially under saturated conditions. Moreover, the distribution of water in the samples directly affected the crack initiation and propagation and characteristics of the fracture morphology.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shear Behavior and Anisotropy Characteristics of the Fracture Morphology of Sandstone with Different Water Contents

Sun

Qin

et al. 2020

Geofluids

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“…Previous studies have mainly focused on fracture expansion direction, formation stress, influencing factors and numerical method modeling [6]. In addition, researches were also focused on the gas flow behavior in the gas extraction process [1,[7][8][9][10], from the early single-phase gas flow model to the later two-phase water-gas flow model [11]. Furthermore, the effects of initial permeability, Young's modulus, water saturation, and other factors on the fluid flow were studied [12].…”

Section: Model Conceptmentioning

confidence: 99%

“…The mass flux J mfα of fluid was obtained from [1]. Forchheimer equation was applied to describe non-Darcy effect, as in [10]. The water and gas mass can be calculated as [14]:…”

Section: Numerical Analysismentioning

confidence: 99%

The Influence of the Injected Water on the Underground Coalbed Methane Extraction

et al. 2020

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The increasing demand on coal production has led to the gradually increase of mining depth and more high methane mines, which bring difficulties in terms of coalbed methane (CBM) extraction. Hydraulic fracturing is widely applied to improve the production of CBM, control mine gas, and prevent gas outbursts. It improves coal bed permeability and accelerate desorption and migration of CBM. Even though the impacts of hydraulic fracturing treatment on the coal reservoirs are rare, negative effects could not be totally ignored. To defend this defect, the presented work aims to study the influence of water filtration on coal body deformation and permeability evolution. For this purpose, a simulation based finite element method was developed to build a solid-fluid coupled two-phase flow model using commercial software (COMSOL Multiphysics 5.4). The model was verified using production data from a long strike borehole from Wangpo coal mine in Shanxi Province, China. Several simulation scenarios were designed to investigate the adverse impacts of hydraulic fracturing on gas flow behaviors. The mechanisms of both relative and intrinsic permeability evolutions were analyzed, and simulation results were presented. Results show that the intrinsic permeability of the fracture system increases in the water injection process. The impacts of water imitation were addressed that a critical time was observed beyond which water cannot go further and also a critical pressure exists above which the hydraulic pressure would impair the gas flow. Sensitivity analysis also showed that a suitable time and pressure combination could be observed to maximize gas extraction. This work provides an efficient approach to guide the coal bed methane exploitation and other unconventional gas reservoirs.

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“…For example, in civil engineering, in situ stress states are fundamental for the design of excavations. In the drilling and completion of shale gas reservoirs, the in situ stress should be considered for wellbore stability analysis, fracture design, as well as reducing asymmetric fractures in a pad area to increase the recovery rate 3,4 . In mining engineering, the in situ stress measurement is vital to maintain the stability of surrounding rock masses 5‐7 .…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of deformation memory effect of rock materials in low‐stress condition using discrete element method

Tang

Zhou

Zhao

2020

Energy Science & Engineering

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The slip behavior of the pre‐existing sliding planes (eg, cracks or inter‐grain boundaries) in rocks is a natural candidate for a mechanism of the deformation memory effect. Based on this mechanism, the deformation rate analysis (DRA) method can be used to measure in situ stress in low‐stress region. However, the traditional discrete element method (DEM) is unable to model the deformation memory effect of rock when the loading stress is lower than the crack initiation stress due to the insufficient consideration for sliding planes. The simulated stress‐strain curves obtained from previous DEM are linear in initial loading stage until cracks start to grow. In the present work, the properties of planes (ie, cohesion, frictional resistance, and relocking mechanism) are introduced into DEM contact model to simulate the deformation memory effect of rock in low‐stress region, and its feasibility was confirmed by comparing it with experimental results. It is found that there exists a suitable in situ stress range for DRA method when using it in low‐stress region, among which the inflection is precise. Four factors related to the sliding planes are discussed with parametric study to study their influence on the deformation memory effect. The results show that the cohesion and dip angle are highly related to the threshold value, while the friction coefficient and fraction of slide planes have little influence on the deformation memory effect in rocks.

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Short‐term failure mechanism triggered by hydraulic fracturing

Cited by 14 publications

References 67 publications

Shear Behavior and Anisotropy Characteristics of the Fracture Morphology of Sandstone with Different Water Contents

Shear Behavior and Anisotropy Characteristics of the Fracture Morphology of Sandstone with Different Water Contents

The Influence of the Injected Water on the Underground Coalbed Methane Extraction

Numerical simulation of deformation memory effect of rock materials in low‐stress condition using discrete element method

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