An assessment method for shale fracability based on fractal theory and fracture toughness

Ji, Guofa; Li, Kuidong; Gong-she, Zhang; Li, Shaoming; Zhang, Lei

doi:10.1016/j.engfracmech.2019.02.011

Cited by 27 publications

(3 citation statements)

References 32 publications

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“…where F i represents the fracability index; α, β, and γ denote the effect contributions of the shale structure, brittleness, and fracture toughness on the fracability, respectively, in which α + β + γ = 1 was simplified to α = β = γ = 1/3 in the current study; and S n , B n , and K n represent the range-normalized RQD I value, brittleness index, and fracture toughness index, respectively. The specific algorithm is shown as follows [41]:…”

Section: Comprehensive Evaluation Methods For Fracabilitymentioning

confidence: 99%

A New Evaluation Method for the Fracability of a Shale Reservoir Based on the Structural Properties

Sui

Gao

2019

Geofluids

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The fracability of shale reservoirs is one of the key indicators used for evaluating whether or not the shale can be used as a “sweet spot zone.” It has been determined that the structural properties of rock have important influences on the evaluation of the fracability of reservoirs. In the current study, five rock quality designation (RQD) calculation methods were compared and analyzed for the purpose of selecting an RQDI for characterizing rock structures. Focused on the lack of structural factors included in the previous fracability evaluation methods, a new model for fracability evaluation based on the combination of the brittleness index, structural index, and fracture toughness was constructed using a linear elastic fracture theory. The model showed that good fracability not only included higher brittleness but also required less energy to produce cracks. Meanwhile, good fracability also required more discontinuous structural planes. In the current study, a formation with a higher fracability index was considered to be a fractureable interval and a formation with a lower fracability index was a fracture barrier. Finally, the reservoir fracability index was modeled using the Xike 2 well in the north of Guizhou Province as a case study. Subsequently, a fracability logging evaluation method based on the fracability index model was determined, which will potentially provide a new technical tool for future fracturing optimization processes.

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Section: Comprehensive Evaluation Methods For Fracabilitymentioning

confidence: 99%

A New Evaluation Method for the Fracability of a Shale Reservoir Based on the Structural Properties

Sui

Gao

2019

Geofluids

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“…The agglomeration of particles also influenced the fractal dimension, with agglomerated structures exhibiting better electrical conductivity than uniform structures. Ji et al applied fractal theory in connecting the fracture toughness with micromorphology [9]. Gurbuz et al presented a study on the impact of shape memory alloy (SMA) fibers on the microstructure and mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced engineered cementitious composites (ECCs) [10].…”

Section: Introductionmentioning

confidence: 99%

Correlation between Agglomerates Hausdorff Dimension and Mechanical Properties of Denture Poly(methyl methacrylate)-Based Composites

Elhmali,

Serpa,

Radojevic

et al. 2024

Fractal Fract

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The microstructure–property relationship in poly(methyl methacrylate) PMMA composites is very important for understanding interface phenomena and the future prediction of properties that further help in designing improved materials. In this research, field emission scanning electron microscopy (FESEM) images of denture PMMA composites with SrTiO3, MnO2 and SrTiO3/MnO2 were used for fractal reconstructions of particle agglomerates in the polymer matrix. Fractal analysis represents a valuable mathematical tool for the characterization of the microstructure and finding correlation between microstructural features and mechanical properties. Utilizing the mathematical affine fractal regression model, the Fractal Real Finder software was employed to reconstruct agglomerate shapes and estimate the Hausdorff dimensions (HD). Controlled energy impact and tensile tests were used to evaluate the mechanical performance of PMMA-MnO2, PMMA-SrTiO3 and PMMA-SrTiO3/MnO2 composites. It was determined that PMMA-SrTiO3/MnO2 had the highest total absorbed energy value (Etot), corresponding to the lowest HD value of 1.03637 calculated for SrTiO3/MnO2 agglomerates. On the other hand, the highest HD value of 1.21521 was calculated for MnO2 agglomerates, while the PMMA-MnO2 showed the lowest Etot. The linear correlation between the total absorbed impact energy of composites and the HD of the corresponding agglomerates was determined, with an R2 value of 0.99486, showing the potential use of this approach in the optimization of composite materials’ microstructure–property relationship.

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“…The development of the world’s economies has led to a rising demand for coal, oil, and gas resources because of increasing pressure to develop energy sources . Shale gas is an important alternative to conventional energy sources and has been used in a wide range of applications. , Shale gas reserves are abundant in China, but shale gas reservoirs are generally characterized as possessing low porosity, low permeability, and a complex microstructure, – thus making it impossible to accurately identify gas transport mechanisms when predicting shale gas production. This poses a huge challenge for shale gas’s development and is an impediment to safe and efficient shale gas production.…”

Section: Introductionmentioning

confidence: 99%

Study of Changes in Apparent Permeability in Shale’s Complex Microfracture Networks

Ding,

Li,

et al. 2023

Ind. Eng. Chem. Res.

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The microfracture structure in the reservoirs of shale has a strong influence on gas transport. To depict the transport characteristics of shale gas in widely developed microfractures, this paper has constructed a shale apparent permeability model based on fractal theory. Shale's microfracture structure was first identified as a bifurcation network, with the effects of effective stress and gas adsorption considered to obtain the dynamic fractal dimension definition equation. Effective viscosity was corrected by employing weighting factors relating to continuum flow viscosity and Knudsen diffusion viscosity. Finally, an apparent permeability model for shale was established by combining the three transport mechanisms of continuum flow, Knudsen's diffusion, and surface diffusion. The model was validated. The results showed that the viscosity flow rate of continuum flow and Knudsen diffusion increased under increasing pore pressure, revealing that the effect of a microfracture bifurcation network on shale's permeability was significant when shale gas was transported.

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An assessment method for shale fracability based on fractal theory and fracture toughness

Cited by 27 publications

References 32 publications

A New Evaluation Method for the Fracability of a Shale Reservoir Based on the Structural Properties

A New Evaluation Method for the Fracability of a Shale Reservoir Based on the Structural Properties

Correlation between Agglomerates Hausdorff Dimension and Mechanical Properties of Denture Poly(methyl methacrylate)-Based Composites

Study of Changes in Apparent Permeability in Shale’s Complex Microfracture Networks

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