Mutual interference of layer plane and natural fracture in the failure behavior of shale and the mechanism investigation

Zhao, Peng; Xie, Lingzhi; Fan, Zhichao; Deng, Lei; Liu, Jun

doi:10.1007/s12182-020-00510-5

Cited by 23 publications

(8 citation statements)

References 56 publications

(49 reference statements)

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“…This permeability enhancement is due to a high probability that the concave–convex bodies on fracture surfaces with greater roughness would provide a self-support system during shearing. − This self-support system will create newly connected pathways and lead to an easier increase in the fracture aperture. Similar mechanisms have been explored via numerical modeling ,,,,− and experimentation. ,,,,, …”

Section: Introductionmentioning

confidence: 88%

Analysis of the Upper and Lower Boundaries of Permeability Evolution during Shale Rock Shear Deformation

Sun

Chen

Zhu³

et al. 2022

Energy Fuels

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Understanding the evolution of permeability during rock shear displacement plays an important role in many geosciences and geo-engineering, such as shale gas exploitation. In previous studies, permeability data were obtained under different experimental conditions with varied in situ stress environments, fracture apertures, or loading stresses. However, the mechanisms controlling the permeability evolution during the shear process have not been well explained. In this study, two special conditions, fractures with constant stiffness (CS) and constant volume (CV), are proposed to define the upper and lower boundaries of permeability evolution. An inverted "L-shaped" model containing a matrix and fracture was established to investigate the permeability evolution and internal morphological changes in the fractures. The impacts of the initial fracture aperture and normal stress in the shear process are discussed together with the apparent fracture aperture, effective flow area, and pore throat radius. Under the CS condition, the self-supporting effect produced by the contact between the upper and lower fracture surfaces plays a dominant role in changing the permeability, and three stages of permeability evolution with shear displacement are observed: rapid increase, slow increase, and decrease. Under CV conditions, the submergence effect of the fracture closed the effective flow channels, thereby reducing the permeability in three stages: rapid decrease, slow decrease, and recovery. The model results show that both a smaller initial fracture aperture or a greater normal stress lead to a greater variation in the permeability and the roughness of fracture surface determines the permeability evolution range. The new model was applied to generate a series of shale permeability evolution boundaries under different limit conditions. These boundaries are consistent with experimental observations reported in other literatures. This work provides new insights into the permeability evolution of rock strata under shear action.

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Section: Introductionmentioning

confidence: 88%

Analysis of the Upper and Lower Boundaries of Permeability Evolution during Shale Rock Shear Deformation

Sun

Chen

Zhu³

et al. 2022

Energy Fuels

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“…Due to the complexity of the sand meso-structure and the limitation of the research, the researchers did not obtain a reliable mechanical theory to establish a quantitative relationship between meso parameters and macro parameters. Currently, the most common method to determine basic contact parameters is the transformation of the macroscopic mechanical properties of samples or large-scale experiments via trial-and-error approach [23].…”

Section: The Dem Methodsmentioning

confidence: 99%

A Discrete Numerical Study of the Effect of the Thickness and the Porosity of the Sand Cushion on the Impact Response Due to the Rockfall

Yuan¹,

Zhao²,

Li³

et al. 2022

Computer Modeling in Engineering &Amp; Sciences

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The prevention and the reduction of the rockfall are the common measures of the prevention and the reduction of disasters. When the rock-shed resists the impact of the rockfall, the force that acts on the structure consists of the cushion dead load and the impact-induced load, of which the dynamic process of the propagation of the impactinduced load is complex. Therefore, we conducted a numerical study to investigate the impact of the rockfall. Considering the highly discrete characteristic of the sand, we developed a numerical model on the basis of the discrete element method (DEM). The numerical model, which simulation results were validated by the results of real-scale experiments, was used to investigate the dynamic response of the impact force of the rockfall and the transmission of the impact force under the different magnitude of the falling height and the different thickness of the sand cushion. The results of our study indicated that the cushion thickness had little effect on the impact of the rockfall, and the dense sand cushion generated higher impact force than did the loose sand cushion. Although the high thickness enhanced the buffer performance of the sand cushion, the additional force induced by the dead load of sand cushion was significant. Therefore, to determine the appropriate thickness of the sand cushion, we suggested designers consider the buffer performance and the dead load of the sand cushion. The analysis presented in this paper provided a practical estimation of the impact-induced force of the thick sand cushion.

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“…This also implies that the shale, as an important target stratum, has a good material basis for shale gas accumulation, and the Wuxi area is considered a favorable shale gas exploration area. Meanwhile, a number of shale gas geological survey wells have also been arranged in this area since 2012 and the WX2 well in the Wenfeng anticline deployed by PetroChina has obtained a good shale gas performance, with 2.32 and 8.39 m 3 /t of mean and maximum gas-bearing contents, showing that the Wufeng−Longmaxi Formation in the area is of favorable shale gas exploration and developmental potential (Liang et al, 2015;Liu et al, 2017;Wu et al, 2017;Shi et al, 2018;Liu et al, 2021b;Zhao et al, 2021;Zhao et al, 2022). Although some shale gas exploration wells have achieved effective exploration results in this area, such as X202, X203, and X205 wells, none of them is up to the commercial production scale.…”

Section: Introductionmentioning

confidence: 99%

Structural deformation characteristics and its influence on shale gas preservation of the Wufeng−Longmaxi Formation in the Wuxi area, Chongqing, China

Luo²,

et al. 2023

Front. Earth Sci.

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The Upper Ordovician Wufeng to Lower Silurian Longmaxi Formation has a good material basis for marine shale gas development, and the structural preservation condition is the key factor to control the rich and integrated shale gas reservoirs in the Wuxi area of Chongqing City, China. Based on the seismic-structural interpretation data, combined with the regional structural background and drilling effect, the structural deformation characteristics and shale gas structural preservation conditions are comprehensively analyzed in the study area. The Wuxi area is located at the structural junction of the Sichuan Basin and southern Dabashan along with strong structural deformations. Seven rows of NW to near EW structural belts are mainly developed. The fold styles and fault development degrees of different structural belts are different, and the difference in the structural preservation conditions of shale gas is also obvious. The study results reveal that the shale gas structure preservation conditions of the Wufeng−Longmaxi Formation in the Wuxi area are overall poor and only locally better. The structure preservation conditions for shale gas enrichment and accumulation are divided into four grades, such as the good Class I area, the general Class II area, the poor Class III area, and the very poor Class IV area. Among them, the Heiloumen structural zone and Huangcaoping buried structural zone nearby the Sichuan Basin have good preservation conditions and are classified as the good Class I preservation area. The macroscopic preservation type of shale gas in the Wufeng−Longmaxi Formation of the Wuxi area belongs to the complex structural preservation of the basin margin. Three structural preservation modes of shale gas in the study area have also been confirmed, including the lost destruction type, lost residual type, and trap preservation type. The trap preservation type is more conducive to the preservation of shale gas, which is the most favorable structural mode for shale gas exploration.

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Mutual interference of layer plane and natural fracture in the failure behavior of shale and the mechanism investigation

Cited by 23 publications

References 56 publications

Analysis of the Upper and Lower Boundaries of Permeability Evolution during Shale Rock Shear Deformation

Analysis of the Upper and Lower Boundaries of Permeability Evolution during Shale Rock Shear Deformation

A Discrete Numerical Study of the Effect of the Thickness and the Porosity of the Sand Cushion on the Impact Response Due to the Rockfall

Structural deformation characteristics and its influence on shale gas preservation of the Wufeng−Longmaxi Formation in the Wuxi area, Chongqing, China

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