Capillary Pressure Curve Determination Based on a 2‐D Cross‐Section Analysis Via Fractal Geometry: A Bridge Between 2‐D and 3‐D Pore Structure of Porous Media

Chen, Xiaojun; Yao, Guangqing; Luo, Chengfei; Jiang, Ping; Cai, Jianchao; Zhou, Kun; Herrero‐Bervera, E.

doi:10.1029/2018jb016722

Cited by 17 publications

(22 citation statements)

References 68 publications

(93 reference statements)

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“…The classical Watershed (WS) algorithm is widely used to segment two connected pore bodies in porous media (Chen et al., 2019; Rabbani et al., 2014). However, whether WS algorithm can segment fracture surface remains unclear.…”

Section: Resultsmentioning

confidence: 99%

“…TS visualizes these invisible pores and microfractures on the mesoscopic scale between macroscopic identification and microscopic SEM. TS was successfully applied in sandstone reservoirs to analyze 2D pore structure and associated diagenesis (the dissolution, compaction of grain and the evolution of clay minerals) (Chen & Yao, 2017; Chen et al., 2019). In this work, microfractures morphologies of coal samples including intact coal (Nos.…”

Section: Materials and Methodologymentioning

confidence: 99%

“…the evolution of clay minerals) Chen et al, 2019). In this work, microfractures morphologies of coal samples including intact coal (Nos.…”

Section: Accepted Articlementioning

confidence: 99%

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Microstructure Analysis on the Fracture Network in High‐Rank Coals

Lyu

Chen

Li³

et al. 2021

Earth and Space Science

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Microfractures in the coal matrix have complex spatial structure because of the joint effects of coalification and tectonism. The accurate modeling and characterization of microfractures directly affect mechanism analysis of coal rock fracturing and mining. In this study, taking the high-rank coal in the north of Qinshui Basin, structural characteristics of microfracture in intact and tectonic coals were analyzed systematically using 2D thin section, 3D micro-CT modeling and mercury intrusion based on digital image analysis and fractal theory. Result indicates that response sensitivity of fractal parameters obtained from different methods to microfractures from two types of coal structures is different greatly. Single fractal dimension (Df) in tectonic coal is higher than that of intact coal. Specially, for 2D thin sections, the indicative effect on the Df of manually-corrected images is better than that of automaticallyextracted and linear ones. Df has a positive correlation with the pixel-based microfracture porosity, as well as generalized fractal parameters. Moreover, microfracture permeability based on the Cubic-Law increases with the increase of Df. For 3D micro-CT modeling, the classical Watershed algorithm cannot segment the spatial microfracture network, which however can be segmented and characterized by the self-developed FracSC3D program. Spatial microstructural parameters including volume, surface and length at three-axis directions meet bi-fractal characteristics.Specially, for 2D micro-CT slices, with the increase of porosity, the multifractal spectrum width Δα also increased.

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Section: Resultsmentioning

confidence: 99%

Section: Materials and Methodologymentioning

confidence: 99%

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Microstructure Analysis on the Fracture Network in High‐Rank Coals

Lyu

Chen

Li³

et al. 2021

Earth and Space Science

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“…If the reference cross section is used as the research object, the relationship between the effective porosity ϕ and the reference porosity ϕ r can be expressed as ϕ = ϕ r c , where c is defined as the nonuniformity factor. However, in practice, the reference porosity is not necessarily greater than the effective porosity [37], so the range of the nonuniformity factor c should be c > 0, more specifically, when the reference porosity is greater than the effective porosity, c > 1; when the reference porosity is less than the effective porosity, 0 < c < 1; and when the reference porosity equals to the effective porosity, c = 1.…”

Section: The Permeability Of Nonuniform Cross-sectional Poresmentioning

confidence: 99%

Relative Permeability of Porous Media with Nonuniform Pores

et al. 2020

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Most classical predictive models of relative permeability conceptualize the pores in porous media as assemblies of uniform capillary tubes with different sizes. However, this simplification may overestimate the transport capacity of porous media due to overlooking the effects of the pore nonuniformity. This study presents a simple way to quantify the effect of the nonuniformity of pore cross section on the transport characteristic of unsaturated porous media. The way is based on the index relationship between the porosity of a newly defined reference cross section and that of porous media, which satisfies the intrinsic constraints for the nonuniform porosity of cross sections in porous media. Moreover, the index factor can be captured by a newly defined parameter, called the nonuniformity factor, which is used to establish an extended Darcy’s law. Based on these, a fractal-based continuous analytical model and a fractal-based Monte Carlo model of relative permeability as well as a permeability-porosity model are established. Experimental data of five wetting-nonwetting phase systems, including the water-air, water-steam, water-nitrogen, water-oil, and oil-gas systems, are selected to assess the performance of the proposed model. The results confirm the proposed model’s capacity in capturing the transport properties of various porous media. It is found that the nonuniformity of pores can significantly increase the resistance of fluid flow and thus reduce the transport capacity of porous media.

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“…In the model, the Sierpinski fractal was utilized to construct the geometry structure of porous media. In the study of Chen et al [34], they demonstrated that one special bridge function, which was a function of the apparent length and tortuosity fractal dimension, could characterize the relationship of pore structures between two dimensions (2-D) and three dimensions (3-D), and it could serve as a conversion bridge of the radius to determine the capillary pressure curve. In view of the evolution characteristics of micropore-throat structure of longterm waterflood reservoir, most scholars described it through laboratory experiments and field coring data, but few scholars proposed to apply fractal theory to it to realize the quantitative characteristics of its change law in theory.…”

Section: Introductionmentioning

confidence: 99%

The Evolutionary Characteristics of Reservoir Microstructure under Long-Term Waterflooding Development and Its Fractal Description

Wang

Liu

et al. 2021

Geofluids

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Generally, long-term waterflooding development often leads to the change of reservoir pore and clay mineral composition, which results in the change of permeability and wettability. In order to explore the relationship between core micropore structure and water cut, based on physical simulation experiments and fractal theory, we proposed a fractal evolutionary model to describe the evolution characteristics of microstructure of long-term water driving reservoirs. In this paper, core pore structure by SEM was first conducted to analyze the change of core pore structure before and after waterflooding under the conditions of magnification of 200 times, 800 times, and 2000 times, respectively. Then, conventional and constant rate mercury injection tests were combined to perform the comparative analysis of core structural parameters before and after waterflooding. Finally, a micropore-throat structure evolution model of core was established. Research shows that the connectivity of larger pores becomes better after long-term water driving, the degree of heterogeneity weakens, and the micro heterogeneity of small pores becomes stronger and stronger. The throat characteristics change in a complex manner, the radius tends to increase, and the sorting becomes better, while the connectivity of small throat changes complex. In general, the heterogeneity of throat increases with the time of water injection in reservoirs with low porosity and permeability. On the basis of fractal theory and variation characteristics of rock pore structure in water driving reservoirs, we have established a micropore-throat structure evolution model of core pore-throat characteristics. This fractal evolution model quantitatively characterized the complexity and evolution law of pore structure and clarified the relationship between fractal dimension of core pore structure and water cut under different stages of water driving.

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Capillary Pressure Curve Determination Based on a 2‐D Cross‐Section Analysis Via Fractal Geometry: A Bridge Between 2‐D and 3‐D Pore Structure of Porous Media

Cited by 17 publications

References 68 publications

Microstructure Analysis on the Fracture Network in High‐Rank Coals

Microstructure Analysis on the Fracture Network in High‐Rank Coals

Relative Permeability of Porous Media with Nonuniform Pores

The Evolutionary Characteristics of Reservoir Microstructure under Long-Term Waterflooding Development and Its Fractal Description

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