A new application of atomic force microscopy in the characterization of pore structure and pore contribution in shale gas reservoirs

Chen, Shangbin; Li, Xueyuan; Chen, Si; Wang, Yan; Gong, Zhuo; Zhang, Yingkun

doi:10.1016/j.jngse.2021.103802

Cited by 26 publications

(16 citation statements)

References 31 publications

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“…This result is consistent with the fractal dimension characteristics of shale lithofacies (Figure 10). The reason is that OM pores well developed in organic-rich siliceous shales provided more PV and SSA (Figures 4a, 12a, and 13a), and the pore form factors of organic-rich siliceous shales are generally greater than those of argillaceous shales, which suggests the more complicated pore boundary of organic-rich shale, 52 as illustrated in Figure 4a,c. This implies that siliceous shales have the most methane adsorption site, that is, the highest adsorption capacity.…”

Section: Discussionmentioning

confidence: 99%

“…However, the clay mineral content has a strong negative correlation with fractal dimension D1 and a weak−moderate negative correlation with fractal dimension D2 (Figure 17c), due to the more concentrated surface height distribution of clay-rich argillaceous shales. 52 The reason is that triangle or slit-shaped pores between the clay minerals are susceptible to compaction in clay-rich shales. Furthermore, there is an extremely strong negative correlation between the fractal dimensions and average pore diameter, which indicates that clay-rich argillaceous shales contain larger pores with simple boundaries (Figure 17d).…”

Section: Discussionmentioning

confidence: 99%

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Study on the Pore Structure and Fractal Characteristics of Different Lithofacies of Wufeng–Longmaxi Formation Shale in Southern Sichuan Basin, China

Qian

Shen

et al. 2022

ACS Omega

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Gas content and flow characteristics are closely related to shale lithofacies, and significant differences exist in the pore structure and fractal characteristics among lithofacies. In this study, X-ray diffractometer (XRD), field-emission scanning electron microscopy (FE-SEM), gas adsorption (N 2 and CO 2 ), and fractal theory were employed to systematically characterize the pore attributes of the marine Wufeng−Longmaxi formation shales. The information of various pores and microfractures among lithofacies was extracted and quantified via high-resolution FE-SEM image stitching technology. Shales were classified into four types based on mineral compositions, and siliceous shales possess the largest SEM-based surface porosity (2.84%) and the largest pore volume (PV) (average 0.0243 cm 3 /g) as well as specific surface area (SSA) (average 28.06 m 2 / g). The effect of lithofacies variation on the PV of shale is minor. In contrast, the lithofacies variation has a significant impact on the SSA, and the SSA of siliceous shale is 39.11% higher than that of argillaceous shale. PV and SSA show strong positive correlation with the total organic carbon (TOC) content but negative correlation with clay minerals. Siliceous shales have the greatest fractal dimension D1 (pore surface roughness) (average 2.6821), which is contributed by abundant organic matter pores with more complicated boundaries. The largest fractal dimension D2 (pore structure complexity) (average 2.8263) is found in mixed shales, which is attributed to well-developed intraparticle (intraP) pores associated with carbonate mineral dissolution. This indicates that siliceous shales have the highest methane adsorption capacity and that shale gas desorption, diffusion, and seepage are more difficult in mixed shales.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Study on the Pore Structure and Fractal Characteristics of Different Lithofacies of Wufeng–Longmaxi Formation Shale in Southern Sichuan Basin, China

Qian

Shen

et al. 2022

ACS Omega

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“…Pore types have recently been systematically described for unconventional reservoir formations, including organic matter pores, interparticle mineral pores, intraparticle mineral pores, and microfractures (Loucks et al, 2012;Clarkson et al, 2013;Milliken et al, 2013). Atomic force microscopy (AFM) is a high-resolution method that integrates both 3D surface morphology and quantitative analysis which have been employed to describe the nanoscale pore structures within organic rocks, facilitating visual characterization or semiquantitative analysis (Zhao et al, 2019;Jubb et al, 2020;Chen et al, 2021). The recent development of atomic force microscopy-based infrared spectroscopy (AFM-IR) was also employed to examine the molecular structure of organic matters to provide an insight into the chemical diversities of an inertinite composition (Jubb et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Pore Connectivity Characterization Using Coupled Wood’s Metal Intrusion and High-Resolution Imaging: A Case of the Silurian Longmaxi Shales From the Sichuan Basin, China

Liu

Fan

et al. 2021

Front. Earth Sci.

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Pore connectivity is crucial for shale gas production. However, the three-dimensional (3D) characteristics and distribution of pore networks and, more fundamentally, the underlying role of different pore types on pore connectivity in shales are inadequately understood. By comparing the 3D pore connectivity derived from direct microstructural imaging of pores filled with Wood’s metal at a pressure corresponding to the finest accessible pore throat in the resolution ranges that may be achieved by X-ray micro-CT and SEM, it is possible to evaluate pore connectivity of different types of shales. The pore connectivity of three shales including a mixed mudstone, siliceous shale, and argillaceous shale from the Silurian Longmaxi Formations is investigated via combined broad ion beam (BIB) polishing, and SEM and X-ray micro-CT imaging after Wood’s metal injection at a pressure up to 380 MPa. The three shales show significant differences in pore connectivity. The mixed mudstone shows excellent pore connectivity in the matrix; the siliceous shale shows an overall poor connectivity with only a small amount of OM (organic matter) pores immediately adjacent to microfractures displaying interconnectivity, while the pores in the argillaceous shale, dominated by plate-like clay pores, are largely not interconnected.

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“…As the roughness decreases, a slippage effect on the porewall surface is obvious, and shale transport capacity is improved. From the surface morphology of shale nanopores, a serious pore surface geometrical heterogeneity or roughness can be usually observed, published literature has observed the surface roughness of shale nanopores by the method of atomic force microscopy (AFM), [25][26][27][28] it can accurately reflect the actual structure of nanopore surface. As shown in Figure 2, a complicated porewall surface heterogeneity can be observed, where the chromaticity in the two-dimensional (2D) map represents the height of pore surface (Figure 2A).…”

Section: Introductionmentioning

confidence: 99%

Adsorption behavior modeling of confined hydrocarbons in shale heterogeneous nanopores by the potential theory

et al. 2022

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In this article, a new method is proposed to quantificationally evaluate the effect of pore heterogeneity on the adsorption behavior of fluids in nanopores. First, the assumptions of furrowed, sinusoidal, and ravine pore surfaces are proposed to represent the heterogeneous nanopores in shale. Under the assumptions, a multicomponent potential theory of adsorption (MPTA) is coupled with Peng–Robinson equation of state (PR EOS) to model the adsorption behavior of hydrocarbons in nanopores. And, the geometrical and chemical heterogeneities in shale nanopores are, respectively, simulated by a spatial alteration and an amplitude deformation on potential energy. The fluid–fluid interaction is modeled by PR EOS, and the fluid‐pore wall surface interaction is simulated by a Steel 10‐4‐3 model for slit‐like nanopores and by a modified Lennard–Jones (LJ) 12‐6 model for cylindrical ones. Thereafter, the results of our theory are compared against the experimental data of shale rocks to validate its accuracy.

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A new application of atomic force microscopy in the characterization of pore structure and pore contribution in shale gas reservoirs

Cited by 26 publications

References 31 publications

Study on the Pore Structure and Fractal Characteristics of Different Lithofacies of Wufeng–Longmaxi Formation Shale in Southern Sichuan Basin, China

Study on the Pore Structure and Fractal Characteristics of Different Lithofacies of Wufeng–Longmaxi Formation Shale in Southern Sichuan Basin, China

Pore Connectivity Characterization Using Coupled Wood’s Metal Intrusion and High-Resolution Imaging: A Case of the Silurian Longmaxi Shales From the Sichuan Basin, China

Adsorption behavior modeling of confined hydrocarbons in shale heterogeneous nanopores by the potential theory

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