Stress distribution properties and deformation–fracture mechanisms in hydraulic fracturing of coal

Fang, Xiaojie; Wu, Caifang; Zhang, Hewei; Han, Jiang; Li, Geng; Gao, Bin; Jiang, Xiuming

doi:10.1016/j.fuel.2023.129049

Cited by 8 publications

(6 citation statements)

References 58 publications

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“…13,14 In addition, microresistivity imaging logging of 10 wells and array acoustic logging of seven wells were used to identify the direction of in situ stress in detail. 11,26 2.1.2. Injection/Falloff Test.…”

Section: Methodsmentioning

confidence: 99%

“…Conventional well logs included gamma ray, spontaneous potential and resistivity logs, acoustic porosity, bulk density, neutron porosity, and acoustic travel time logs. The Young’s modulus, density, Poisson’s ratio, and other parameters of the coal rock can be calculated from these conventional logging data (see Section for details). , In addition, microresistivity imaging logging of 10 wells and array acoustic logging of seven wells were used to identify the direction of in situ stress in detail. , …”

Section: Methodsmentioning

confidence: 99%

“…The brighter the image, the higher the resistivity of the formations is. The images can be divided into static images and dynamic images. ,, …”

Section: Methodsmentioning

confidence: 99%

“…The images can be divided into static images and dynamic images. 26,31,32 By analyzing the stresses in the well wall are analyzed, there is a maximum shear stress around the well in the direction of σ h . When the stress exceeds the shear strength of the rock, the borehole wall produces a stress collapse phenomenon (Figure 2a,b).…”

Section: 2mentioning

confidence: 99%

“…There are different models for calculating horizontal stresses, including the Anderson Model based on the Moore-Cullen rupture criterion; with all parameters based on the sonic logging model developed using logging data; Huang’s model that introduces the tectonic stress coefficient, but the effect of Young’s modulus is ignored; the combined spring model that considers the horizontal deformation is constant; and Ge’s model accounting for the effects of formation temperature and tectonic stresses on horizontal principal stresses. − However, each calculation model has limitations and cannot be generally used in different areas due to the different geological backgrounds. Furthermore, the in situ stress field significantly influences the steering and extension of hydraulic fractures, which should be carefully considered before gas production. − …”

Section: Introductionmentioning

confidence: 99%

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Detailed in Situ Stress Characterization Combining Well Logging and Improved Magnitude Calculation Model of Nos. 8+9 Coal Seam in Northeastern Ordos Basin

Wang,

Li,

et al. 2024

Energy Fuels

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The characteristics of in situ stress directly influence reservoir modification and gas production performance, and accurate evaluation of stress distribution can help improve coalbed methane production and development efficiency. Taking the deep carboniferous Nos. 8+9 coal seam in the northeastern Ordos Basin as an example, different in situ stress calculation models were evaluated with comparison to injection/falloff tests based on logging data and coal mechanical parameters. Then, the hydraulic fracture extension mechanism under different in situ stress conditions was simulated. The results show that the comprehensive use of microresistivity imaging logging and dipole array acoustic logging reveals that the main maximum horizontal principal stress direction of the Nos. 8+9 coal seam is E–W, with some area affected by faults showing NE–SW and SEE–NWW. Comparing the commonly used acoustic logging model, Huang’s model, the combined spring model, and Ge’s model, it was found that the combined spring model is more applicable. This model was optimized by adding a gas saturation parameter, decreasing the relative error of stress magnitude from 7.80 to 3.62% compared to the injection/falloff measurement results. The stress field shows vertical stress > maximum horizontal principal stress > minimum horizontal principal stress. The simulation indicates that the higher the horizontal stress difference, the smaller the fracture initiation pressure and width. The larger the injection angle, the higher the fracture initiation pressure and the smaller fracture width. The above results reveal the in situ stress distribution characteristics of the Nos. 8+9 coal seam in the northeastern Ordos Basin, providing data support for the subsequent deployment of wells and reservoir fracturing as well as guidance for deep coal seams in other basins.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…The brighter the image, the higher the resistivity of the formations is. The images can be divided into static images and dynamic images. ,, …”

Section: Methodsmentioning

confidence: 99%

Section: 2mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Detailed in Situ Stress Characterization Combining Well Logging and Improved Magnitude Calculation Model of Nos. 8+9 Coal Seam in Northeastern Ordos Basin

Wang,

Li,

et al. 2024

Energy Fuels

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Evolution law of pulsating seepage and thermal deformation by injecting high‐temperature steam into coal for thermal coalbed methane recovery

Li,

Chen

et al. 2024

Deep Underground Science and Engineering

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Chinese coal reservoirs are characterized by low pressure and low permeability, which need to be enhanced so as to increase production. However, conventional methods for permeability enhancement can only increase the permeability in fractures, but not the ultra‐low permeability in coal matrices. Attempts to enhance such impermeable structures lead to rapid attenuation of gas production, especially in the late stage of gas extraction. Thermal stimulation by injecting high‐temperature steam is a promising method to increase gas production. The critical scientific challenges that still hinder its widespread application are related to the evolution law of permeability of high‐temperature steam in coal and the thermal deformation of coal. In this study, an experimental approach is developed to explore the high‐temperature steam seepage coupled with the thermal deformation in coal under triaxial stress. The tests were conducted using cylindrical coal specimens of ϕ50 mm × 100 mm. The permeability and thermal strain in coal were investigated when high‐temperature steam was injected at 151.11, 183.20, 213.65, and 239.76°C. The experimental results reveal for the first time that as the amount of injected fluid increases, the steam permeability shows periodic pulsation changes. This paper introduces and explains the main traits of this discovery that may shed more light on the seepage phenomenon. When the injected steam temperature increases, the amplitude of pulsating permeability decreases, whereas the frequency increases; meanwhile, the period becomes shorter, the pulsation peak appears earlier, and the stabilization time becomes longer. The average peak permeability shows a “U‐shaped” trend, decreasing first and then increasing as the steam temperature increases. Meanwhile, with the extension of steam injection time, the axial, radial, and volumetric strains of coal show a stage‐wise expansion characteristic at different temperatures of steam injection, except for the radial strains at 151.11°C. A two‐phase flow theory of gas–liquid is adopted to elucidate the mechanism of pulsating seepage of steam. Moreover, the influencing mechanism of inward and outward thermal expansion on the permeability of coal is interpreted. The results presented in this paper provide new insight into the feasibility of thermal gas recovery by steam injection.

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Dynamic stress response and fatigue characteristics of tight sandstone reservoirs with pulsating hydraulic fracturing

Zhu,

Hanane,

Dong

et al. 2024

Bull Eng Geol Environ

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Stress distribution properties and deformation–fracture mechanisms in hydraulic fracturing of coal

Cited by 8 publications

References 58 publications

Detailed in Situ Stress Characterization Combining Well Logging and Improved Magnitude Calculation Model of Nos. 8+9 Coal Seam in Northeastern Ordos Basin

Detailed in Situ Stress Characterization Combining Well Logging and Improved Magnitude Calculation Model of Nos. 8+9 Coal Seam in Northeastern Ordos Basin

Evolution law of pulsating seepage and thermal deformation by injecting high‐temperature steam into coal for thermal coalbed methane recovery

Dynamic stress response and fatigue characteristics of tight sandstone reservoirs with pulsating hydraulic fracturing

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