Multiscale Fractal Analysis in Unconventional Reservoirs, 2nd Edition

A special issue of Fractal and Fractional (ISSN 2504-3110). This special issue belongs to the section "Engineering".

Deadline for manuscript submissions: 30 November 2026 | Viewed by 1722

Editors

School of Resources and Geoscience, China University of Mining and Technology, Xuzhou 221116, China
Interests: shale gas; coalbed methane; pore structure; adsorption mechanism; fractal characterization
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Guest Editor
School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
Interests: unconventional gas recovery; carbon storage; gas diffusion/seepage behaviors; fractal characterization

Special Issue Information

Dear Colleagues,

Unconventional reservoirs, such as shale gas, tight oil, and coalbed methane, have become pivotal in meeting the global energy demand. However, their inherent geological complexity and heterogeneity present significant challenges for accurate characterization, modeling, and efficient extraction. Multiscale fractal analysis offers a robust framework to quantify and interpret the intricate spatial patterns and scaling behaviors within these reservoirs. By applying fractal geometry across multiple scales, researchers can gain deeper insights into fracture networks, pore structures, and fluid flow dynamics, ultimately enhancing reservoir performance and hydrocarbon recovery.

Following the success of the first edition of the Special Issue, titled “Multiscale Fractal Analysis in Unconventional Reservoirs”, with this second edition, we continue to compile innovative research that leverages fractal and multiscale methodologies to address the complexities of unconventional hydrocarbon reservoirs. We invite contributions that explore theoretical advancements, novel computational techniques, and practical applications of multiscale fractal analysis in various aspects of reservoir engineering. Topics of interest include, but are not limited to, the following:

  • Fractal characterization of fracture networks and pore geometries;
  • Multiscale modeling of fluid flow and transport phenomena;
  • Integration of fractal analysis with seismic interpretation and well logging;
  • Application of fractal-based methods in reservoir simulation and optimization;
  • Case studies demonstrating the practical implementation of multiscale fractal techniques;
  • Synergies between fractal analysis and other advanced technologies, such as machine learning and digital rock physics.

By bringing together diverse perspectives and cutting-edge advancements, the focus of this Special Issue is to foster interdisciplinary collaboration and drive forward the understanding and exploitation of unconventional reservoirs. We encourage researchers and industry professionals to share their latest findings, methodologies, and case studies, contributing to the advancement of sustainable and efficient energy extraction practices.

We invite you to read and download all our published articles in the first edition at the following link:

https://www.mdpi.com/journal/fractalfract/special_issues/JSDL837386

Dr. Yang Wang
Dr. Xiaowei Hou
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fractal and Fractional is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • multiscale fractal analysis
  • unconventional reservoirs
  • fractal geometry
  • fracture network characterization
  • pore structure analysis
  • fluid flow modeling
  • reservoir simulation
  • machine learning
  • digital rock physics

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Related Special Issue

Published Papers (3 papers)

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Research

24 pages, 7453 KB  
Article
Fractal Metrics and Pore Architecture as Determinants of Diffusion in High-Rank Coal Reservoirs of the Mengjin Coalfield, Henan Province
by Zixuan Liu, Detian Yan, Shangbin Chen and Derek Elsworth
Fractal Fract. 2026, 10(5), 329; https://doi.org/10.3390/fractalfract10050329 - 11 May 2026
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Abstract
Understanding the pore structure of high-rank coals is essential in evaluating gas storage and transport. Here, twelve semianthracite samples from the early Permian Shanxi Formation were investigated by proximate analysis, optical microscopy, low-temperature N2 adsorption, and fractal analysis, coupled with diffusion coefficient [...] Read more.
Understanding the pore structure of high-rank coals is essential in evaluating gas storage and transport. Here, twelve semianthracite samples from the early Permian Shanxi Formation were investigated by proximate analysis, optical microscopy, low-temperature N2 adsorption, and fractal analysis, coupled with diffusion coefficient modeling. The coals exhibit diverse pore types (plant-cellular, interparticle, and dissolution pores) shaped by coalification and minerals and show Type IV (a) isotherms with H4 hysteresis loops, indicating complex pore networks. Pore-size partitioning reveals that mesopores and macropores dominate total pore volume, whereas mesopores contribute most of the specific surface area. The pore structure exhibits strong fractal characteristics with an average comprehensive fractal dimension (Fc) of 2.628. The calculated gas diffusion coefficient decreases monotonically with increasing pressure from 1 MPa to 5.8 MPa, with a more pronounced decline at low pressure, indicating a clear pressure-dependent attenuation effect. Diffusion capacity is weakly related to average pore diameter but shows positive correlations with total pore volume and, particularly, macropore volume. Multiple linear regression further demonstrates that pore volume structure is the dominant control on diffusion under both low- and high-pressure conditions, with the relative importance ranked as macropores > mesopores > micropores. Macropores provide the main low-resistance transport framework, mesopores serve as transitional pathways linking storage and transport domains, whereas micropores mainly contribute to gas storage and may even suppress apparent diffusion when overly developed. These results reveal a clear functional differentiation of multiscale pore systems and highlight that gas migration in semianthracite is jointly governed by pore size distribution, connectivity, tortuosity, and fractal network topology. Full article
(This article belongs to the Special Issue Multiscale Fractal Analysis in Unconventional Reservoirs, 2nd Edition)
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14 pages, 16925 KB  
Article
Three-Dimensional Fractal Modeling and Construction of Flow Capacity (kh) from Well Logs: A Case Study in Southeastern Mexico
by Sergio Matias-Gutierres, Edgar Israel García-Otamendi, Hugo David Sánchez-Chávez and Roberto Cifuentes-Villafuerte
Fractal Fract. 2026, 10(5), 318; https://doi.org/10.3390/fractalfract10050318 - 8 May 2026
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Abstract
Reservoir evaluation and interpretation are fundamental for production and reserve management, and they require, as a key input, an information matrix describing petrophysical properties within the static model. This study provides the scalar distribution of the petrophysical property associated with flow capacity, [...] Read more.
Reservoir evaluation and interpretation are fundamental for production and reserve management, and they require, as a key input, an information matrix describing petrophysical properties within the static model. This study provides the scalar distribution of the petrophysical property associated with flow capacity, kh (where k is permeability and h is sample thickness). This distribution is generated in a three-dimensional space from six locally distributed well-log series. These well logs were derived from measurement, evaluation, calibration, and interpretation processes and correspond to producing reservoirs in southeastern Mexico. To characterize the heterogeneity of the well-log data through the Hurst exponent, the structure-function metric was employed. Subsequently, these exponents were distributed throughout the three-dimensional domain of interest by linear interpolation. Finally, pseudo-well logs for the studied reservoir were generated using the random midpoint displacement algorithm. A local petrophysical information matrix for the kh property containing 52,800 pseudo-records was obtained. The resulting information matrix is suitable for capturing both fine- and coarse-scale heterogeneity. The methodology applied here suggests a substantial saving in reservoir analysis as a first approximation to the evaluation model. Full article
(This article belongs to the Special Issue Multiscale Fractal Analysis in Unconventional Reservoirs, 2nd Edition)
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30 pages, 24264 KB  
Article
Impact of Multifractal Characteristics of Cross-Scale Pores Under Coal Deformation Constraints on Hydraulic Fracturing
by Yingjin Wang, Quanliang Zou, Xiaowei Hou, Guanqun Zhou, Jiazhong Qian and Haichun Ma
Fractal Fract. 2026, 10(5), 280; https://doi.org/10.3390/fractalfract10050280 - 23 Apr 2026
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Abstract
Coalbed methane (CBM) development is strongly controlled by pore structure evolution in deformed coals and its influence on hydraulic fracturing behavior. To clarify the multifractal characteristics of cross-scale pores and their control on fracturing effectiveness, this study investigated eight different deformation coals from [...] Read more.
Coalbed methane (CBM) development is strongly controlled by pore structure evolution in deformed coals and its influence on hydraulic fracturing behavior. To clarify the multifractal characteristics of cross-scale pores and their control on fracturing effectiveness, this study investigated eight different deformation coals from the Ordos Basin using low-temperature CO2/N2 adsorption (LT-CO2A/LT-N2A) and high-pressure mercury intrusion porosimetry (HMIP). Micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm) were systematically characterized, and their pore size distributions (PSDs) were quantitatively analyzed using the Coal Structure Index (CSI) and multifractal theory. The results indicate that the multifractal parameters of macropores are significantly distinct from those of mesopores and micropores, exhibiting lower H (0.824–0.893) and D1 (0.766–0.853), and higher α0 (1.422–1.541), ΔD (1.230–1.408), and Δα (1.459–1.642). Macropores controlled by tectonic deformation exhibit stronger heterogeneity compared to mesopores and micropores in local parts of the coal mass; PSD varies significantly with deformation rising, derived from the differential pore structure evolution during brittle–ductile transition and the multi-scale synergistic effects including maturity and composition. Combined with field fracturing curves, the results further indicate that the α0, ΔD, and Δα of macropores are negatively correlated with breakdown pressure, with correlation coefficients of 0.51, 0.61, and 0.59, respectively, and that strong local heterogeneity of macropores favors fracture initiation and propagation and reduces breakdown pressure. Cataclastic coal is the most favorable for hydraulic fracturing, followed by undeformed coal, whereas granulated coal shows the poorest fracturing performance. Full article
(This article belongs to the Special Issue Multiscale Fractal Analysis in Unconventional Reservoirs, 2nd Edition)
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