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Fractal Fract
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Pore Structure and Fractal Characteristics in Unconventional Oil and Gas...
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Pore Structure and Fractal Characteristics in Unconventional Oil and Gas Reservoirs

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

Deadline for manuscript submissions: 30 November 2024 | Viewed by 3564

Special Issue Editors

Dr. Zine El Abiddine Fellah

E-Mail Website
Guest Editor
Laboratory of Mechanics and Acoustics, French National Centre for Scientific Research LMA, CNRS, UMR 7031, Centrale Marseille, Aix-Marseille University CEDEX 20, F-13402 Marseille, France
Interests: porous materials; micropolar and fractal materials; fractional calculus; ultrasonic and low frequency characterization; acoustic propagation; vibroacoustic; alloys; direct and inverse problem solving; optimization
Special Issues, Collections and Topics in MDPI journals
Dr. Jizhen Zhang

E-Mail Website
Guest Editor
1. Key Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, Yangtze University, Wuhan 430100, China
2. Laboratory of Reservoir Microstructure Evolution and Digital Characterization, Yangtze University, Wuhan 430100, China
Interests: pore structure; pore heterogeneity; complexity; fractal characteristics
Dr. Quanzhong Guan

E-Mail Website
Guest Editor
Energy College, Chengdu University of Technology, Chengdu 610059, China
Interests: shale gas/oil; pore structure; pore heterogeneity; fractal characteristics; reservoir characteristics

Special Issue Information

Dear Colleagues,

Fractals possess self-similar patterns repeated at different scales and spatially. Many applications have been found for fractals, not only because of their beauty, which has itself received attention, but also because their governing rules simplify complex features in nature. The length and volume of a fractal are related to its characteristic size. Researchers have used fractals to model transport properties of porous media. There has been a growing interest in using fractals for understanding the transport properties of tight formations. Researchers have employed fractals to capture the heterogeneity of stimulated volume, complex geometries of fractures, and change in apparent and relative permeabilities. Fractals have found applications in analyzing the topology of the pore space. Researchers have used fractals to model transport properties of porous media. There has been a growing interest in using fractals for understanding the transport properties of tight formations. The pore structure and their fractal characteristics can have a significant effect on the spatial distributions of the wetting and nonwetting phases, occurrence, enrichment, and flow migration of unconventional oil and gas, which play a significant role in the theoretical research and exploration and development deployment of unconventional oil and gas resources.

In this Special Issue “Pore Structure and Fractal Characteristics in Unconventional Oil and Gas Reservoirs", we would like to solicit your innovative ideas and work regarding the investigation and application of fractal dimensions in geological and geophysical science in the form of original articles. In addition, your study could focus on any aspect of geological and geophysical science, such as geological and geophysical material properties, numerical analysis, experimental and theoretical verifications, etc. The purpose of this Special Issue is to promote the deeper and wider investigation and application of fractal theory in fields of geological and geophysical science. The submitted manuscripts will be peer reviewed, and those accepted will be published in the open access journal Fractal and Fractional. The topics to be considered in this Special Issue include, but are not limited to, the following:

  • Earth science;
  • Microstructures of shale, tight sandstone and coal;
  • Geotechnical engineering;
  • Engineering geology;
  • Granular aggregate properties;
  • Modelling of cracking behavior;
  • The impact of fractal characteristics on reservoirs;
  • Fractal characteristics of fractures;
  • Experimental and theoretical study.

Dr. Zine El Abiddine Fellah
Dr. Jizhen Zhang
Dr. Quanzhong Guan
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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-blind 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

  • pore structure
  • pore heterogeneity
  • complexity
  • fractal characteristics
  • microstructures
  • fractal cracks

Published Papers (4 papers)

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Research

24 pages, 9384 KiB  
Article
Fractal Dimension Analysis of Pore Throat Structure in Tight Sandstone Reservoirs of Huagang Formation: Jiaxing Area of East China Sea Basin
by Wenguang Wang, Chengyan Lin and Xianguo Zhang
Fractal Fract. 2024, 8(7), 374; https://doi.org/10.3390/fractalfract8070374 - 26 Jun 2024
Viewed by 737
Abstract
The reservoir quality of tight sandstone is usually affected by pore throat structures, and understanding pore throat structures and their fractal characteristics is crucial for the exploration and development of tight sandstone gas. In this study, fractal dimensions of pore throat structures and [...] Read more.
The reservoir quality of tight sandstone is usually affected by pore throat structures, and understanding pore throat structures and their fractal characteristics is crucial for the exploration and development of tight sandstone gas. In this study, fractal dimensions of pore throat structures and the effect of diagenesis on the fractal dimension of tight sandstone sweet spot in Huagang Formation, Jiaxing area, East China Sea Basin were studied by means of thin sections, scanning electron microscopes, X-ray diffraction analysis, scanning electron microscope quantitative mineral evaluation, and high pressure mercury injection experiments. The results show that the total fractal dimension ranges of type I, type II, and type III sweet spots were 2.62–2.87, 2.22–2.56, and 2.71–2.77, respectively. The negative correlation between total fractal dimensions, porosity, and permeability of type I sweet spots was different from those of type II and type III sweet spots. The negative correlation between total fractal dimensions of type II and type III sweet spots and maximum mercury saturation, average pore throat radius, and skewness were significant, whereas the correlation between total fractal dimensions of type I sweet spots, and maximum mercury saturation, average pore throat radius and skewness were not significant. The positive correlation between the total fractal dimensions of type II and type III sweet spots and the relative sorting coefficient, displacement pressure, and efficiency of mercury withdrawal were significant, whereas the correlation between the total fractal dimension of type I sweet spots and relative sorting coefficients, displacement pressures and efficiency of mercury withdrawal were not significant. The effect of diagenesis on fractal dimensions was investigated. Compaction reduced the pore space of tight sandstone and increased fractal dimensions. Quartz cementation and calcite cementation blocked pores and throats, reduced pore space, and increased fractal dimensions. Chlorite coat can inhibit compaction, protect pore throat structures, and maintain fractal dimensions. Most clay minerals filled primary pores and secondary pores and increased fractal dimensions. Dissolution increased the pore space of tight sandstone and decreased the fractal dimensions of the pore throat structures. The pore throat structures of type I sweet spots were mainly composed of macropores, mesopores, transitional pores, and micropores, and the fractal dimension of type I sweet spots was chiefly controlled by chlorite coat formation, dissolution, and a small amount of compaction. This study provides a reference for pore throat structure and fractal dimension analysis of tight sandstone sweet spots. Full article
(This article belongs to the Special Issue Pore Structure and Fractal Characteristics in Unconventional Oil and Gas Reservoirs)
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19 pages, 1262 KiB  
Article
Pore Structure Characterization and Fractal Characteristics of Tight Limestone Based on Low-Temperature Nitrogen Adsorption and Nuclear Magnetic Resonance
by Wei Lin, Xinli Zhao, Mingtao Li and Yan Zhuang
Fractal Fract. 2024, 8(7), 371; https://doi.org/10.3390/fractalfract8070371 - 25 Jun 2024
Viewed by 760
Abstract
Pore structure characterization and fractal analysis have great significance for understanding and evaluating tight limestone reservoirs. In this work, the pore structure of tight limestone, low-temperature nitrogen adsorption (LTNA), and low-field nuclear magnetic resonance (NMR) are characterized, and the fractal dimension of the [...] Read more.
Pore structure characterization and fractal analysis have great significance for understanding and evaluating tight limestone reservoirs. In this work, the pore structure of tight limestone, low-temperature nitrogen adsorption (LTNA), and low-field nuclear magnetic resonance (NMR) are characterized, and the fractal dimension of the pore structure of tight limestone is discussed based on LTNA and NMR data. The results indicate that the pores of tight limestone have H3 and H4 types, the pore size distribution (PSD) of the H3 type is a wave distribution ranging from 2 to 10 nm, and the PSD of the H4 type is a unimodal distribution ranging from 2 to 10 nm. The transverse relaxation time (T2) spectrum of tight limestone shows a single peak (DF), double peak (SF), and triple peak (TF), and the ranges for the T2 spectra for micropores, mesopores, and macropores are 0.1 to 10 ms, 10 to 100 ms, and greater than 100 ms, respectively. The LTNA fractal dimension of tight limestone (DL) ranges between 2.4446 and 2.7688, with an average of 2.5729, and the NMR fractal dimensions of micropores (DNMR1), mesopores (DNMR2), and macropores (DNMR3) are distributed between 0.3744 and 1.1293, 2.4263 and 2.9395, and 2.6582 and 2.9989, respectively. Moreover, there is a negative correlation between DL and average pore radius, a positive correlation between DL and specific surface area, and a positive correlation between DNMR2 and DNMR3 and micropore content, while DNMR2 and DNMR3 are negatively correlated with the content of mesopores and macropores. Full article
(This article belongs to the Special Issue Pore Structure and Fractal Characteristics in Unconventional Oil and Gas Reservoirs)
19 pages, 7496 KiB  
Article
Fractal Characterization of the Pore-Throat Structure in Tight Sandstone Based on Low-Temperature Nitrogen Gas Adsorption and High-Pressure Mercury Injection
by Taping He, Yaoqi Zhou, Zhaobing Chen, Zhenwei Zhang, Huanyu Xie, Yuehan Shang and Gaixia Cui
Fractal Fract. 2024, 8(6), 356; https://doi.org/10.3390/fractalfract8060356 - 14 Jun 2024
Viewed by 480
Abstract
The pore-throat structure is a critical factor in the study of unconventional oil and gas reservoirs, drawing particular attention from petroleum geologists, and it is of paramount significance to analyze to enhance oil and gas production. In tight sandstone, which serves as a [...] Read more.
The pore-throat structure is a critical factor in the study of unconventional oil and gas reservoirs, drawing particular attention from petroleum geologists, and it is of paramount significance to analyze to enhance oil and gas production. In tight sandstone, which serves as a significant hydrocarbon reservoir, the internal pore-throat structure plays a decisive role in the storage and migration of fluids such as water, gases, and hydrocarbons. This paper employs casting thin section (CTS), field emission scanning electron microscope (FE-SEM), high-pressure mercury injection (HPMI), and low-temperature nitrogen gas adsorption (LT−N2−GA) experimental tests to qualitatively and quantitatively analyze the characteristics of the pore-throat structure in tight sandstone. The results indicate that the pore types in tight sandstone include intergranular residual pores, dissolution pores, intercrystalline pores, and microfractures, while the throat types encompass sheet-shaped, curved-sheet-shaped, and tubular throats. Analysis of the physical and structural parameters from 13 HPMI and 5 LT−N2−GA samples reveals a bimodal distribution of pore-throat radii. The complexity of the pore-throat structure is identified as a primary controlling factor for reservoir permeability. The fractal dimension (D) exhibits an average value of 2.45, displaying a negative correlation with porosity (R2 = 0.22), permeability (R2 = 0.65), the pore-throat diameter (R2 = 0.58), and maximum mercury saturation (R2 = 0.86) and a positive correlation with threshold pressure (R2 = 0.56), median saturation pressure (R2 = 0.49), BET specific surface area (R2 = 0.51), and BJH total pore volume (R2 = 0.14). As D increases, reservoir pores tend to decrease in size, leading to reduced flow and deteriorated physical properties, indicative of a more complex pore-throat structure. Full article
(This article belongs to the Special Issue Pore Structure and Fractal Characteristics in Unconventional Oil and Gas Reservoirs)
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29 pages, 13316 KiB  
Article
Pore Fractal Characteristics between Marine and Marine–Continental Transitional Black Shales: A Case Study of Niutitang Formation and Longtan Formation
by Shitan Ning, Peng Xia, Fang Hao, Jinqiang Tian, Yong Fu and Ke Wang
Fractal Fract. 2024, 8(5), 288; https://doi.org/10.3390/fractalfract8050288 - 13 May 2024
Viewed by 870
Abstract
Marine shales from the Niutitang Formation and marine–continental transitional shales from the Longtan Formation are two sets of extremely important hydrocarbon source rocks in South China. In order to quantitatively compare the pore complexity characteristics between marine and marine–continental transitional shales, the shale [...] Read more.
Marine shales from the Niutitang Formation and marine–continental transitional shales from the Longtan Formation are two sets of extremely important hydrocarbon source rocks in South China. In order to quantitatively compare the pore complexity characteristics between marine and marine–continental transitional shales, the shale and kerogen of the Niutitang Formation and the Longtan Formation are taken as our research subjects. Based on organic petrology, geochemistry, and low-temperature gas adsorption analyses, the fractal dimension of their pores is calculated by the Frenkel–Halsey–Hill (FHH) and Sierpinski models, and the influences of total organic carbon (TOC), vitrinite reflectance (Ro), and mineral composition on the pore fractals of the shale and kerogen are discussed. Our results show the following: (1) Marine shale predominantly has wedge-shaped and slit pores, while marine–continental transitional shale has inkpot-shaped and slit pores. (2) Cylindrical pores are common in organic matter of both shale types, with marine shale having a greater gas storage space (CRV) from organic matter pores, while marine–continental transitional shale relies more on inorganic pores, especially interlayer clay mineral pores, for gas storage due to their large specific surface area and high adsorption capacity (CRA). (3) The fractal characteristics of marine and marine–continental transitional shale pores are influenced differently. In marine shale, TOC positively correlates with fractal dimensions, while in marine–continental shale, Ro and clay minerals have a stronger influence. Ro is the primary factor affecting organic matter pore complexity. (4) Our two pore fractal models show that the complexity of the shale in the Longtan Formation surpasses that of the shale in the Niutitang Formation, and type I kerogen has more complex organic matter pores than type III, aiding in evaluating pore connectivity and flow effectiveness in shale reservoirs. Full article
(This article belongs to the Special Issue Pore Structure and Fractal Characteristics in Unconventional Oil and Gas Reservoirs)
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