Fractal Characteristics of Shales Across a Maturation Gradient

Chen, Yanyan; Zou, Caineng; Hu, Suyun; Zhu, Rixiang; Bai, Baojun

doi:10.1111/1755-6724.12302_7

Cited by 6 publications

(5 citation statements)

References 12 publications

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“…The components of type II kerogen are a mixture of both types I and III. Zhang , 2012 conducted isothermal adsorption experiments with different types of kerogen and indicated that type III kerogen has the highest adsorption capacity, followed by type II and type I. Chen et al (Chen et al, 2015) showed that the adsorption capacity of different kerogen types followed the following order: type II 2 > type II 1 > type I. Generally, the adsorption capacity order of different kerogen types is as follows: type II/III or type III> type I or type II (Chalmers and Bustin, 2008;Zhang, 2012;Jiang et al, 2016) (Figure 5).…”

Section: Change Of Gas Adsorption Behaviors On Shalementioning

confidence: 99%

“…Heterogeneity of pore size distribution plays an important role in the adsorption process. Pore structure is more complex, porosity and surface area are larger, and the adsorption capacity increases (Heller and Zoback, 2014;Hinai et al, 2014;Chen et al, 2015;Li et al, 2016) (Figures 7A,B). Kim et al (2017) studied the Horn River Basin shale in northeastern British Columbia and found that even in the case of low organic carbon content, adsorption capacity is still strong, as long as the specific surface area is large.…”

Section: Pore Characterizationmentioning

confidence: 99%

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The influencing factors of gas adsorption behaviors in shale gas reservoirs

Lin

Liu²,

Wang³

2023

Front. Earth Sci.

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The adsorption state is one of the main states for shale gas occurrence, and the gas adsorption behavior in shale directly affects shale gas content under reservoir conditions. This paper provides a comprehensive literature review on shale gas adsorption behavior and its affecting factors that have been developed in recent years. Influence factors of gas adsorption behavior are examined, including total organic carbon content (TOC), organic matter type, organic matter maturity, minerals and clay minerals, moisture content, pore characteristics and other characteristics of the shale itself. The characteristics of gas adsorption behavior under high temperature and pressure conditions showed that adsorption behaviors were difficult to describe by the Langmuir equation. This review indicates that shale contains higher organic matter content and organic matter maturity and has a higher adsorption capacity. The adsorption capacity with type III kerogen is higher than that for type II or type I. Clay minerals can provide free space for gas adsorption and promote adsorption. Normally, as the moisture content increased, adsorption capacity decreased. Micro pores provided a larger specific surface area for gas adsorption. As the temperature increased, the adsorption capacity decreased. As the pressure increased, shale adsorption characteristics showed two different behaviors as follows: one obeyed the Langmuir equation, and the other presented an inverted, U-shaped, single-peak distribution. However, there are some controversies surrounding adsorption, especially regarding the aspects of clay minerals, water content, pore characteristics, etc. The key is that the mechanism of adsorption in shale is unclear. There will be many new challenges in the field of shale gas adsorption research. Such challenges include studying the organic matter chemical structure, understanding the interaction between organic matter and clay minerals and how they affect adsorption, clarifying gas adsorption behavior changes, predicting favorable areas of adsorbed gas with the coupling of reservoir temperature and pressure, and building a better theory and model of shale gas adsorption.

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Section: Change Of Gas Adsorption Behaviors On Shalementioning

confidence: 99%

Section: Pore Characterizationmentioning

confidence: 99%

The influencing factors of gas adsorption behaviors in shale gas reservoirs

Lin

Liu²,

Wang³

2023

Front. Earth Sci.

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“…The fractal dimension can be calculated by the mercury intrusion method using the Menger sponge fractal model to characterize the three-dimensional spatial structure of the coal body and then introducing the Washburn equation [26][27][28][29]:…”

Section: Pore Fractal Theorymentioning

confidence: 99%

Coupled Seepage Mechanics Model of Coal Containing Methane Based on Pore Structure Fractal Features

Zhu

et al. 2022

Fractal Fract

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The paper applies fractal theory to the structure of fractal coal pores and calculates the fractal dimension and integrated fractal dimension for each pore section >100 nm, 100 nm > d > 5.25 nm, and <2 nm. In the experiment, we performed the full stress–strain-seepage experiment of methane-bearing coal, revealed the deformation–seepage characteristics of methane-bearing coal under load, and deduced the dynamic prediction mechanical model of methane-bearing coal permeability based on pore heterogeneity, followed by practical verification. The results show that the permeability change in methane-bearing coal is an external manifestation of coal pore deformation, and the two are closely related and affected by changes in the effective stress coefficient. The derived fractal-deformation-coupled methane permeability mechanics model based on coal pore heterogeneity has high accuracy, a general expression for the stress–strain-permeability model based on coal heterogeneity is given, and the fractal Langmuir model is verified to be highly accurate (>0.9) and can be used for coal reservoir permeability prediction.

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“…So, the pore structure of the reservoir space can be quantitatively characterized by fractal theory [45,49]. The fractal dimension of pore structure is distributed between 2 and 3; 2 means that the pore surface is absolutely smooth and 3 means that it is absolutely rough [47][48][49][50]. These two conditions are absolutely impossible in the field of actual geology.…”

Section: Introductionmentioning

confidence: 99%

“…Generally, the smaller the fractal dimension, the more homogeneous the structure of the pore throat, and the larger the fractal dimension, the more heterogeneous the structure of pore throat, where the pore throat refers to the pores and the narrower throat connecting different pores. The research methods for fractal characteristics mainly focus on image analysis [46,51], constant velocity mercury injection [50], high-pressure mercury injection [27,44], gas adsorption [43,52,53], nuclear magnetic resonance, and so on [19]. Mature fractal mathematical models include the FHH (Frenkel-Halsey-Hill) model [54,55], BET model [43,52,56], Menger sponge model, NK model, capillary bundle model, and thermodynamic model [57].…”

Section: Introductionmentioning

confidence: 99%

Heterogeneity of Micro- and Nanopore Structure of Lacustrine Shales with Complex Lamina Structure

Liu,

Qiao,

Zeng

et al. 2024

Fractal Fract

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Thin sections, AIM-SEM, MICP, and nitrogen adsorption were performed on laminated and layered shales to characterize their complex pore and fracture structure. Combining the MICP model with the FHH model, this work proposes a new fractal method for lacustrine shales with complex lamina structure. The fractal characteristics presented four zones, representing the heterogeneity of fractures, macropores, mesopores, and micropores. The pores and fractures of shale have strong heterogeneity. Laminated shale has strong heterogeneity in mesopores and moderate heterogeneity in micropores. Layered shale has strong heterogeneity in fractures and moderate heterogeneity in micropores. The lamina structure and content of organic and mineral composition has a great influence on heterogeneity. The mineral laminae in laminated shale change frequently; lamellation fractures are mainly developed, and the structures are similar. Layered shales develop fractures between layers and structural fractures; the structural differences are significant. Macropores are mostly interparticle pores between quarts with similar structures. The wider lamina thickness of layered shale provides sufficient crystallization space for minerals, so the mesopores of layered shale are more homogeneous. Micropores are less developed, mainly consisting of intraparticle pores between clay minerals, which are complex but similar in structure in the two types of shale. The heterogeneity of mesopores and micropores is not conducive to hydrocarbon migration. Fractures and macropores need to be connected with meso–micropores to form a transport system. So, mesopores and micropores play decisive roles in hydrocarbon migration. Based on the above understanding, this paper points out that hydrocarbon in laminated shale with more carbonate minerals and a high thermal evolution degree has better availability.

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Fractal Characteristics of Shales Across a Maturation Gradient

Cited by 6 publications

References 12 publications

The influencing factors of gas adsorption behaviors in shale gas reservoirs

The influencing factors of gas adsorption behaviors in shale gas reservoirs

Coupled Seepage Mechanics Model of Coal Containing Methane Based on Pore Structure Fractal Features

Heterogeneity of Micro- and Nanopore Structure of Lacustrine Shales with Complex Lamina Structure

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