Nano-scale pore structure and fractal dimension of organic-rich Wufeng-Longmaxi shale from Jiaoshiba area, Sichuan Basin: Investigations using FE-SEM, gas adsorption and helium pycnometry

Yang, Rui; He, Sheng; Jiang, Yi; Hu, Qinhong

doi:10.1016/j.marpetgeo.2015.11.019

Cited by 467 publications

(372 citation statements)

References 72 publications

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“…These negative relationships are consistent with previous studies, 37,61,62 implying that lacustrine shales with smaller average pore size tend to have a more complex pore structure.…”

Section: Relationships Between Fractal Dimensions and Pore Structure supporting

confidence: 92%

Morphology and Fractal Characterization of Multiscale Pore Structures for Organic-Rich Lacustrine Shale Reservoirs

Wang

Zhu

et al. 2018

Fractals

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Lacustrine shale gas has received considerable attention and has been playing an important role in unconventional natural gas production in China. In this study, multiple techniques, including ¶ Corresponding author. This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. total organic carbon (TOC) analysis, X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM), helium pycnometry and low-pressure N 2 adsorption have been applied to characterize the pore structure of lacustrine shale of Upper Triassic Yanchang Formation from the Ordos Basin. The results show that organic matter (OM) pores are the most important type dominating the pore system, while interparticle (interP) pores, intraparticle (intraP) and microfractures are also usually observed between or within different minerals. The shapes of OM pores are less complex compared with the other two pore types based on the Image-Pro Plus software analysis. In addition, the specific surface area ranges from 2.76 m 2 /g to 10.26 m 2 /g and the pore volume varies between 0.52 m 3 /100g and 1.31 m 3 /100g. Two fractal dimensions D 1 and D 2 were calculated using Frenkel-Halsey-Hill (FHH) method, with D 1 varying between 2.510 and 2.632, and D 2 varying between 2.617 and 2.814. Further investigation indicates that the fractal dimensions exhibit positive correlations with TOC contents, whereas there is no definite relationship observed between fractal dimensions and clay minerals. Meanwhile, the fractal dimensions increase with the increase in specific surface area, and is negatively correlated with the pore size. 1840013-1

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“…These negative relationships are consistent with previous studies, 37,61,62 implying that lacustrine shales with smaller average pore size tend to have a more complex pore structure.…”

Section: Relationships Between Fractal Dimensions and Pore Structure supporting

confidence: 92%

Morphology and Fractal Characterization of Multiscale Pore Structures for Organic-Rich Lacustrine Shale Reservoirs

Wang

Zhu

et al. 2018

Fractals

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“…In our LPNA experiments, the PSD curves exhibit the unimodal nature for most of the shale samples, and the peak is at approximately 4 nm (Fig. 1b), which is consistent with the results conducted by other researchers for Longmaxi shale (Wang et al, 2016b;Yang et al, 2016). The mesopore volumes of the shale samples are mainly contributed by the pores with width between 2 and 10 nm, which is also consistent with the observations in Wang et al (2016b).…”

Section: Resultssupporting

confidence: 92%

“…The adsorption characteristics of shale gas has been studied intensively in the last decade, mainly by experiments and molecular simulations (Clarkson et al, 2013;Mosher et al, 2013;Rexer et al, 2013;He et al, 2016;Tang et al, 2016;Tian et al, 2016;Xiong et al, 2017). Extensive studies on the methane adsorption capacity and its controlling factors in various shale formations have been conducted, showing that the total organic carbon (TOC) is a main contributor to the adsorbed gas capacity (Ross et al, 2009;Weniger et al, 2010;Gasparik et al, 2012;Zhang et al, 2012;Ji et al, 2015;Wang et al, 2016a;Zhao et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Investigation of methane adsorption mechanism on Longmaxi shale by combining the micropore filling and monolayer coverage theories

Zhou

Yang

Wang

et al. 2018

Adv. Geo-Energy Res.

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Abstract:Understanding the methane adsorption mechanism is critical for studying shale gas storage and transport in shale nanopores. In this work, we conducted low-pressure nitrogen adsorption (LPNA), scanning electron microscopy (SEM), and high-pressure methane adsorption experiments on seven shale samples from the Longmaxi formation in Sichuan basin. LPNA and SEM results show that pores in the shale samples are mainly nanometersized and have a broad size distribution. We have also shown that methane should be not only adsorbed in micropores (< 2 nm) but also in mesopores (2-50 nm) by two hypotheses. Therefore, we established a novel DA-LF model by combining the micropore filling and monolayer coverage theories to describe the methane adsorption process in shale. This new model can fit the high-pressure isotherms quite well, and the fitting error of this new model is slightly smaller than the commonly used D-A and L-F models. The absolute adsorption isotherms and the capacities for micropores and mesopores can be calculated using this new model separately, showing that 77% to 97% of methane molecules are adsorbed in micropores. In addition, we conclude that the methane adsorption mechanism in shale is: the majority of methane molecules are filled in micropores, and the remainder are monolayer-adsorbed in mesopores. It is anticipated that our results provide a more accurate explanation of the shale gas adsorption mechanism in shale formations.

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“…Fractal dimension correlates well with the pore volume and surface area (Bu et al, 2015;Sun et al, 2015Sun et al, , 2016Yang et al, 2014Yang et al, , 2016. The Longmaxi and Qiongzhusi are the extensively studied shale formations in southern China Sun et al, 2016;Tian et al, 2015;Xue et al, 2016;Yan et al, 2016;Yang et al, 2016;Zeng et al, 2016;Zhang et al, 2015). The study of rich organic matter shale in the late Paleozoic marine-terrigenous facies in Qinshui Basin, northern China, is relatively new and there exists only few studies.…”

Section: Introductionmentioning

confidence: 99%

Pore characteristics of organic-rich shale in the Carboniferous-Permian coal-bearing strata in Qinshui Basin

Gao

Wei

Song

et al. 2017

Energy Exploration & Exploitation

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The study of shale pore has always been an important aspect of nonconventional shale reservoir analysis. However, there are relatively few studies on shale that is deposited in transitional environment in the Qinshui Basin. X-ray diffraction, field-emission scanning electron microscopy, N 2 , and CO 2 adsorption experiments were used for shale samples from the Taiyuan and Shanxi Formations. Sample pore characteristics based on field-emission scanning electron microscopic photographs were quantitatively characterized by pore fracture characteristics analysis software and fractal characteristics were discussed based on the nitrogen adsorption curve. Results show that sample pores were primarily composed of inter-granular and intra-granular pores. The proportion of micropores (<2 nm) is 25.84-91.65% of the total pore space, with an average of 58.65%. Micropores show three peaks, which occur near 0.38 nm, 0.5 nm, and 0.85 nm. Mesopores (2-50 nm) account for 6.74-56.11% of the total pore space, with an average of 31.20%. The ratio of macropores (>50 nm) less than 100 nm is 1.61-20.64% with an average of 9.17%. The volume of micropores increases with increase in the total organic carbon and clay mineral contents, decreases with the increase of carbonate and quartz mineral contents, and has weak correlation with other factors. The micropore volume per unit organic matter decreases with increase in maximum vitrinite reflectance (R o,max ) in a binomial relationship. The correlations between meso-macropore volume and each factor are rather weak. Form factor, fractal dimension, and probability entropy all correlate well with the depth. Pore structure complexity gradually increases with the increase in the burial depth. The deeper the rock layer increases with the pore size, the more slowly the pore complexity increases. The larger pore diameter, the more smooth journals.sagepub.com/home/eea the pore wall surface, and the rougher surface is more favorable for gas adsorption. The directionality of pore development increases first and then decreases with increase in the depth.

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Nano-scale pore structure and fractal dimension of organic-rich Wufeng-Longmaxi shale from Jiaoshiba area, Sichuan Basin: Investigations using FE-SEM, gas adsorption and helium pycnometry

Cited by 467 publications

References 72 publications

Morphology and Fractal Characterization of Multiscale Pore Structures for Organic-Rich Lacustrine Shale Reservoirs

Morphology and Fractal Characterization of Multiscale Pore Structures for Organic-Rich Lacustrine Shale Reservoirs

Investigation of methane adsorption mechanism on Longmaxi shale by combining the micropore filling and monolayer coverage theories

Pore characteristics of organic-rich shale in the Carboniferous-Permian coal-bearing strata in Qinshui Basin

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