Multiscale Apparent Permeability Model of Shale Nanopores Based on Fractal Theory

Wang, Qiang; Hu, Yongquan; Zhao, Jinzhou; Ren, Lan; Zhao, Chaoneng; Zhao, Jin

doi:10.3390/en12173381

Cited by 19 publications

(11 citation statements)

References 49 publications

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“…Black shale, as a nonconventional reservoir, has typical low porosity and low permeability characteristics [1][2][3][4][5]. The nanoscale pores in the shale constitute a complex pore network [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Fractal Characteristics of Micro- and Mesopores in the Longmaxi Shale

2020

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To better understand the variability and heterogeneity of pore size distributions (PSDs) in the Longmaxi Shale, twelve shale samples were collected from the Xiaoxi and Fendong section, Sichuan Province, South China. Multifractal analysis was employed to study PSDs of mesopores (2–50 nm) and micropores (<2 nm) based on low-pressure N2/CO2 adsorption (LP-N2/CO2GA). The results show that the PSDs of mesopores and micropores exhibit a multifractal behavior. The multifractal parameters can be divided into the parameters of heterogeneity (D−10–D10, D0–D10 and D−10–D0) and the parameters of singularity (D1 and H). For both the mesopores and micropores, decreasing the singularity of the pore size distribution contributes to larger heterogeneous parameters. However, micropores and mesopores also vary widely in terms of the pore heterogeneity and its controlling factors. Shale with a higher total organic carbon (TOC) content may have a larger volume of micropores and more heterogeneous mesopores. Rough surface and less concentrated pore size distribution hinder the transport of adsorbent in mesopores. The transport properties of micropores are not affected by the pore fractal dimension.

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Section: Introductionmentioning

confidence: 99%

Fractal Characteristics of Micro- and Mesopores in the Longmaxi Shale

2020

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“…As shown in Figure 2, there are two types of clusters: loose mode I cluster (Figure 2a) and compact mode II cluster (Figure 2d). Type I cluster is the structural combination of particles that can form the largest pore space, while type II cluster is the structural Fractal theory describes a natural phenomenon, which allows the self-similarity of objects to represent the properties of objects or scale invariance, and is an effective method to describe the complexity and irregularity of pores in porous media and their related macroscopic transport characteristics [14][15][16][17]. The application of fractal theory to the study of porous media is actually to use an appropriate method or model to characterize the structural characteristics of porous media, and then analyze its properties such as transmission and strain [18,19].…”

Section: Fractal Characteristics Of Spherical Particles Matrixmentioning

confidence: 99%

A Novel Porous Media Permeability Model Based on Fractal Theory and Ideal Particle Pore-Space Geometry Assumption

Wang

Zhao

et al. 2020

Energies

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In this paper, a novel porous media permeability model is established by using particle model, capillary bundle model and fractal theory. The three-dimensional irregular spatial characteristics composed of two ideal particles are considered in the model. Compared with previous models, the results of our model are closer to the experimental data. The results show that the tortuosity fractal dimension is negatively correlated with porosity, while the pore area fractal dimension is positively correlated with porosity; The permeability is negatively correlated with the tortuosity fractal dimension and positively correlated with the integral fractal dimension of pore surface and particle radius. When the tortuosity fractal dimension is close to 1 and the pore area fractal dimension is close to 2, the faster the permeability changes, the greater the impact. Different particle arrangement has great influence on porous media permeability. When the porosity is close to 0 and close to 1, the greater the difference coefficient is, the more the permeability of different arrangement is affected. In addition, the larger the particle radius is, the greater the permeability difference coefficient will be, and the greater the permeability difference will be for different particle arrangements. With the increase of fractal dimension, the permeability difference coefficient first decreases and then increases. When the pore area fractal dimension approaches 2, the permeability difference coefficient changes faster and reaches the minimum value, and when the tortuosity fractal dimension approaches 1, the permeability difference coefficient changes faster and reaches the minimum value. Our research is helpful to further understand the connotation of medium transmission in porous media.

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“…In order to establish a complete fluid-solid coupled model, Darcy's law is used to establish a coupling fluid filtration model with permeability, fluid pressure, and pore pressure as the variable terms 52,53 :…”

Section: Fluid Filtrationmentioning

confidence: 99%

Study on induced stress of hydraulic fracturing in fractured‐porous elastic media

Wang

Zhao

et al. 2020

Energy Science & Engineering

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The study on induced stress of hydraulic fracturing is an important part of hydraulic fracturing design, temporary plugging and steering fracturing design, and completion design in oil and gas development. Based on fracture continuum method (FCM), cohesive unit method, and finite volume method (FVM), the propagation behavior of multiple hydraulic fractures (HFs) in fractured‐porous media reservoir is simulated from the perspective of fluid and geological stress coupling. The influence of natural fractures (NFs) on stress distribution and stress inversion sensitive factors are studied. NFs in the model are equivalent to physical models controlled by tension and shear bonds. The proposed model can deal with any number of NFs, which greatly improves the computational efficiency of the model. Then PKN analytic solution and Abaqus software results were used to verify the correctness of our model. The results show that the NF will make the reservoir stress show strong heterogeneity after fracturing, and the prominent feature is the regional stress mutation. The sudden change of stress shows the sudden increase or decrease in stress; with the increase in the initial stress difference, the stress inversion becomes more difficult. When the stress difference exceeds 3 MPa, the stress inversion area is almost 0. The stress interference increases with the decrease in cluster spacing. The stress inversion region between HFs decreases, while the external stress inversion region increases; Biot coefficient has great influence on stress and stress inversion. With the decrease in Biot coefficient, stress inversion region will decrease obviously. When the Biot coefficient is 0.4, there is no stress inversion area in the whole reservoir. Poisson's ratio has little influence on stress inversion. When Poisson's ratio changes between 0.1 and 0.3, the change range of stress is within 1 MPa, and the stress inversion area is almost unchanged. Our results can be helpful for understanding the stress distribution after hydraulic fracturing in fractured‐porous media.

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Multiscale Apparent Permeability Model of Shale Nanopores Based on Fractal Theory

Cited by 19 publications

References 49 publications

Fractal Characteristics of Micro- and Mesopores in the Longmaxi Shale

Fractal Characteristics of Micro- and Mesopores in the Longmaxi Shale

A Novel Porous Media Permeability Model Based on Fractal Theory and Ideal Particle Pore-Space Geometry Assumption

Study on induced stress of hydraulic fracturing in fractured‐porous elastic media

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