Nanoscale pore structure and fractal characteristics of a marine-continental transitional shale: A case study from the lower Permian Shanxi Shale in the southeastern Ordos Basin, China

Yang, Chao; Zhang, Jinchuan; Wang, Xiangzeng; Tang, Xuan; Chen, Yongchang; Jiang, Lulu; Gong, Xue

doi:10.1016/j.marpetgeo.2017.07.021

Cited by 96 publications

(89 citation statements)

References 58 publications

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“…A positive relationship was observed between TOC content and BET SSA and BJH PV (Figure 7a,b), which was consistent with several previous studies [9,[54][55][56]. However, we note that correlations with BET SSA were stronger than they were with BJH PV.…”

Section: Effect Of Toc Content On Pore Structuresupporting

confidence: 92%

“…The distinct relationships between quartz content and PV and SSA may be due to the different origins of quartz. The biogenic quartz in marine shale typically contained a large number of pores and may work together with OM to change the pore structure in shale [14,19,61], whereas the quartz in marinecontinental transitional shale or continental shale was mainly terrigenous and theoretically contributed little to the SSA and PV and had little influence on the pore structure [56]. Although the types of quartz were not examined for these samples, most of the quartz should not be biogenic according to Figure 3a.…”

Section: Effect Of Mineral Composition On Pore Structurementioning

confidence: 99%

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Pore Structure and Fractal Characteristics of Niutitang Shale from China

Tang

Wang

et al. 2018

Minerals

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A suite of shale samples from the Lower Cambrian Niutitang Formation in northwestern Hunan Province, China, were investigated to better understand the pore structure and fractal characteristics of marine shale. Organic geochemistry, mineralogy by X-ray diffraction, porosity, permeability, mercury intrusion and nitrogen adsorption and methane adsorption experiments were conducted for each sample. Fractal dimension D was obtained from the nitrogen adsorption data using the fractal Frenkel-Halsey-Hill (FHH) model. The relationships between total organic carbon (TOC) content, mineral compositions, pore structure parameters and fractal dimension are discussed, along with the contributions of fractal dimension to shale gas reservoir evaluation. Analysis of the results showed that Niutitang shale samples featured high TOC content (2.51% on average), high thermal maturity (3.0% on average), low permeability and complex pore structures, which are highly fractal. TOC content and mineral compositions are two major factors affecting pore structure but they have different impacts on the fractal dimension. Shale samples with higher TOC content had a larger specific surface area (SSA), pore volume (PV) and fractal dimension, which enhanced the heterogeneity of the pore structure. Quartz content had a relatively weak influence on shale pore structure, whereas SSA, PV and fractal dimension decreased with increasing clay mineral content. Shale with a higher clay content weakened pore structure heterogeneity. The permeability and Langmuir volume of methane adsorption were affected by fractal dimension. Shale samples with higher fractal dimension had higher adsorption capacity but lower permeability, which is favorable for shale gas adsorption but adverse to shale gas seepage and diffusion.

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Section: Effect Of Toc Content On Pore Structuresupporting

confidence: 92%

Section: Effect Of Mineral Composition On Pore Structurementioning

confidence: 99%

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Tang

Wang

et al. 2018

Minerals

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“…Fishman et al (2012) and Mathia et al (2016) found few isolated, round, and oval pores with well-defined boundaries developed in terrestrial macerals and their size may reach up to 0.5-1 µm. Yang et al (2016Yang et al ( , 2017b also reported that no noticeable traces of hydrocarbon-bubble pores developed in the vitrinite and inertinite grains in transitional shale, which is considerably consistent with our studies. Hence, the terrestrial macerals (mainly vitrinites) are regarded as an unfavorable component for the OM pore development in the Longtan Formation mudrocks.…”

Section: Controlling Factors For the Om Pore Developmentsupporting

confidence: 92%

“…8a-f). According to previous studies (Yang et al, , 2017bLiu et al, 2017;Zhang et al, 2017b;Cao et al, 2018), vitrinite and inertinite appear as discrete grains in mineral matrix, and pores are rarely observed via SEM. The organic macerals in the studied Longtan Formation mudrocks primarily contain vitrinite and inertinite; therefore, OM pores cannot be detected in the FE-SEM images despite their sufficiently high maturity.…”

Section: Fe-sem Observation and Pore Developmentmentioning

confidence: 86%

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Nanoscale Pore Characteristics of the Upper Permian Mudrocks from a Transitional Environment in and around Eastern Sichuan Basin, China

Cao

Liu

et al. 2019

Acta Geologica Sinica (Eng)

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Nanoscale pore characteristics of the Upper Permian Longtan transitional mudrocks and their equivalent strata Wujiaping Formation marine mudrocks in and around the eastern Sichuan Basin was investigated using field emission scanning electron microscopy (FE‐SEM) and low‐pressure N2 adsorption experiments. The results indicate that the Upper Permian mudrock is at a mature stage with total organic carbon (TOC) values ranging between 0.47% and 12.3%. The Longtan mudrocks mainly contain vitrinite, and their mineral composition is primarily clay. In contrast, the Wujiaping mudrocks are dominated by sapropelinite and solid bitumen, and their mineral compositions are mainly quartz and a notably high amount of pyrite. The FE‐SEM reveals that clay mineral pores and microcracks are the common pore types in the Longtan mudrocks. The specific surface area and pore volume depend on the clay content but are negatively correlated with the TOC. The generation of nanometer pores in the Longtan mudrocks is caused by high clay mineral contents. Meanwhile, the Wujiaping mudrock mainly contains OM pores, and the pore parameters are positively correlated with the TOC. The OM pore development exhibits remarkable differences in the Longtan and Wujiaping mudrocks, which might be related to their sedimentary facies and maceral fractions. Vitrinite and inertinite appear as discrete particles in these mudrocks and cannot generate pores during thermal maturation. Sapropelinite often contains many secondary pores, and solid bitumen with large particles, usually with several pores, is not the major contributor to the pore system of the investigated mudrock.

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Pore structure and fractal characteristics of transitional shales with different lithofacies from the eastern margin of the Ordos Basin

Wang,

Deng,

et al. 2023

Energy Science & Engineering

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To better characterize the heterogeneity of transitional shale pore structure and understand its impact on shale gas enrichment, fine characterization of the pore structure of different shale lithofacies was performed by field‐emission scanning electron microscopy, high‐pressure mercury injection, low‐temperature N2 adsorption, and low‐pressure CO2 adsorption. Fractal theory was used to obtain the fractal dimension of the shale pores at different scales and reveal the relationships among the pore structural characteristics, mineral composition, total organic carbon content, and fractal dimension of the shale and their geological significance. The results showed that organic pores, intergranular pores, intragranular pores, and microcracks were generally developed in the transitional shale samples from the study area; elliptic or irregular organic pores were mainly developed in the argillaceous shale lithofacies and siliceous shale lithofacies, and wedge‐shaped or irregular intragranular pores were mainly developed in the calcareous shale lithofacies. The pore size distribution showed a multipeak pattern, and mesopores were the main contributors to the total pore volume (PV), while micropores and macropores contributed little to the total PV. The PV and specific surface area of the siliceous shale were lower than those of the argillaceous shale but higher than those of the calcareous shale, indicating that the change in lithofacies had a significant effect on the shale pores. The common influence of clay minerals, quartz content, and total organic carbon content results in strong heterogeneity and complex pore structure characteristics of shale reservoirs. The pores in the transitional shale from the study area had obvious multiscale fractal characteristics, and the fractal dimension characteristics of different lithofacies and pores at different scales were different, which reflected that the pore structure of the shale had strong heterogeneity. The heterogeneity of the shale pores mainly originated from the macropores and mesopores, while the heterogeneity of micropores was relatively low. The heterogeneity of the pore development and structure at different scales was controlled by the mineral composition matter and organic matter abundance to varying degrees.

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Nanoscale pore structure and fractal characteristics of a marine-continental transitional shale: A case study from the lower Permian Shanxi Shale in the southeastern Ordos Basin, China

Cited by 96 publications

References 58 publications

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Nanoscale Pore Characteristics of the Upper Permian Mudrocks from a Transitional Environment in and around Eastern Sichuan Basin, China

Pore structure and fractal characteristics of transitional shales with different lithofacies from the eastern margin of the Ordos Basin

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