Stress-dependence of the permeability, porosity, and compressibility in fractured porous media regarding fracturing condition

Bagherzadeh, Parisa; Goshtasbi, Kamran; Kazemzadeh, Ezatallah; Kashef, Mojtaba; Bakhtiari, H Aloki

doi:10.1007/s10064-021-02215-4

Cited by 12 publications

(3 citation statements)

References 28 publications

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“…[1][2][3] Exploring the correlations among permeability, porosity, and compressibility under varying stresses provides insights into unraveling the mechanisms behind these processes. [4][5][6] Experiments and analytical models have been developed to analyze the mechanisms governing the evolution of rock properties in response to varying stresses. The experiments involve subjecting rock specimens to diverse confining stresses and pore pressures, replicating the stress conditions in underground environment, [7][8][9][10] allowing for the measurement of rock properties such as permeability, porosity, and compressibility.…”

Section: Stress-dependent Properties Of Rockmentioning

confidence: 99%

“…Investigating stress‐dependent properties of rock plays a pivotal role in understanding the mechanisms underlying geo‐mechanical processes, including hydrology, geophysics, and reservoir engineering 1–3 . Exploring the correlations among permeability, porosity, and compressibility under varying stresses provides insights into unraveling the mechanisms behind these processes 4–6 …”

Section: Introductionmentioning

confidence: 99%

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Interpreting correlations in stress‐dependent permeability, porosity, and compressibility of rocks: A viewpoint from finite strain theory

Wang,

Zhang

2024

Num Anal Meth Geomechanics

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Characteristics of stress‐dependent properties of rocks are commonly described by empirical laws. It is crucial to establish a universal law that connects rock properties with stress. The present study focuses on exploring the correlations among permeability, porosity, and compressibility observed in experiments. To achieve this, we propose a novel finite strain‐based dual‐component (FS‐DC) model, grounded in the finite strain theory within the framework of continuum mechanics. The FS‐DC model decomposes the original problem into the rock matrix and micro‐pores/cracks components. The deformation gradient tensor is utilized to derive the constitutive relations. One of the novelties is that the stress‐dependent variables are calculated in the current configuration, in contrast to the reference configuration used in small deformation theory. The model has only a few number of parameters, each with specific physical interpretations. It can be reduced to existing models with appropriate simplifications. Then, model performance is examined against experimental data, including permeability, porosity, compressibility, volumetric strain and specific storage. It proves that the variations of these properties are effectively described by the proposed model. Further analysis reveals the effect of pores/cracks parameters. The validity of the FS‐DC model is examined across a broad range of pressures. The results show that rock properties at high confining pressures (300 MPa) differ from those observed under relatively low pressures (200 MPa). This disparity can be attributed to inelastic behaviors of micro‐structure, wherein the rock skeleton undergoes permanent deformation and breakage.

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Section: Stress-dependent Properties Of Rockmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interpreting correlations in stress‐dependent permeability, porosity, and compressibility of rocks: A viewpoint from finite strain theory

Wang,

Zhang

2024

Num Anal Meth Geomechanics

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“…The Brazilian splitting method is used to create microfractures in shale, and shale samples containing natural fractures are used to study the change law of the gas permeability in the fractures. − The permeability of shale fractures is affected by the effective stress along different paths. ,, The internal pressure remains unchanged, and the increase in the external pressure can help effectively reduce the permeability of shale fractures. ,, The relationship between the effective stress and shale fracture permeability can be characterized using the exponential model and power model. ,− In addition to the effective stress, the permeability of shale fractures is affected by the external temperature , and gas adsorption characteristics. , The fracture characteristics of the shale itself cannot be ignored. The fracture conductivity is positively correlated with the penetration and opening of fractures. ,,− The permeability of shale fractures is affected by the roughness and tortuosity of the fractures and also by the gas slippage phenomenon. − As a result, the measured permeability is greater than the actual value. The lower the pore pressure, the more evident the slippage effect and the greater the error in the measured permeability …”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Effects of Pore Pressure and Slippage on the Permeability of a Fracture Network during Depressurization of Shale Gas Reservoir Production

Zhao

Sun

et al. 2022

ACS Omega

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Hydraulic fracturing technology is an important technical means to increase shale gas production. The seepage channels formed in the hydraulic fractures during hydraulic fracturing can help increase reservoir permeability. Therefore, it is of significance to study the seepage law of the fracture network after reservoir hydraulic fracturing. In this study, hydraulic fracturing is used to fracture full-diameter shale cores, and three typical forms of hydraulic fracture networks are obtained. The characteristics of the fracture networks are analyzed by X-ray CT scanning. The effects of pore pressure and slippage on the permeability of the fracture networks are simulated by conducting experiments. The experimental results show that in the direction of gas seepage, hydraulic fractures completely penetrate the sample, and the greater the diameter and volume of the fracture, the better the hydraulic fracture conductivity. When the confining pressure remains unchanged at 50 MPa, the apparent permeability values of the hydraulic fractures with the worst and best fracture morphologies increase by 44.4 times and 2.8 times, respectively, with the decrease in the pore pressure from 30 to 2 MPa. The apparent permeability of the shale samples has a power function relationship with the pore pressure. The test results also show that the absolute permeability is positively correlated with the number of effective seepage channels in the hydraulic fractures and the number of hydraulic fractures, whereas the Klinkenberg coefficient is negatively correlated. Our research results can provide a basis for shale gas production model research and for on-site production capacity improvement. The qualitative understanding and scientific explanation of the effects of pore pressure and slippage on fracture network permeability in the process of depressurization of reservoir production have been realized.

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The combined effect of fractures and mineral content on coal hydromechanical response

Bahaaddini

Masoumi

et al. 2022

Bull Eng Geol Environ

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The hydromechanical behaviour of fractured coal is a complex function of interaction between coal bulk and fracture deformation driven by fluid pressure and external stress. Despite the research studies conducted to date, the combined effect of mineral content and fracture structure on hydromechanical behaviour of sorptive fractured coal remains unexplored. To study this combined effect, we performed a series of X-ray computed tomography (XRCT) imaging on a range of coal specimens with non-sorbing (helium) and sorbing (CO2) gases at different effective stress paths using a newly developed X-ray transparent triaxial system. The compressibility of system components was obtained from processed 3D XRCT images which were used to interpret the results. The results of this study show that coal matrix/solid compressibility has a positive nonlinear relation with mineral content irrespective of mineral type. Effective stress coefficient is also a strong function of both mineral content and fracture porosity. Furthermore, the increase in mineral content leads to less fracture opening by an increase in helium pressure. Interestingly, the effect of mineral content on the bulk strength of coal is more significant than the effect of fracture porosity. Finally, coal with more open fractures shows less bulk swelling by gas adsorption under external stress due to damping effect of fracture volume on developed internal volumetric swelling strain.

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Stress-dependence of the permeability, porosity, and compressibility in fractured porous media regarding fracturing condition

Cited by 12 publications

References 28 publications

Interpreting correlations in stress‐dependent permeability, porosity, and compressibility of rocks: A viewpoint from finite strain theory

Interpreting correlations in stress‐dependent permeability, porosity, and compressibility of rocks: A viewpoint from finite strain theory

Experimental Study on the Effects of Pore Pressure and Slippage on the Permeability of a Fracture Network during Depressurization of Shale Gas Reservoir Production

The combined effect of fractures and mineral content on coal hydromechanical response

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