Pore structure heterogeneity of Wufeng-Longmaxi shale, Sichuan Basin, China: Evidence from gas physisorption and multifractal geometries

Wang, Yan; Cheng, Hongfei; Hu, Qinhong; Liu, Luofu; Jia, Langbo; Gao, Shasha; Wang, Ye

doi:10.1016/j.petrol.2021.109313

Cited by 78 publications

(44 citation statements)

References 51 publications

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“…Kerogen pores are the main locations of adsorbed gas and free gas. The pore structures have been the focus in many studies. − Nitrogen adsorption, , mercury intrusion porosimetry, , and helium ion microscopy have been used to characterize the pore structure and connectivity of kerogen, revealing that kerogen is abundant of micro- (<2 nm), meso- (2–50 nm), and macro-pores (>50 nm). − Bazilevskaya et al found that over 50% pores in shale are smaller than 20 nm in size. Chiang et al revealed that kerogen with higher maturity has a larger pore volume and a larger contactable specific surface area.…”

Section: Introductionmentioning

confidence: 99%

Gas Adsorption Capacity of Type-II Kerogen at a Varying Burial Depth

Wen

Zhang

et al. 2022

Energy Fuels

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Kerogen is the main host of methane in most shale formations. Although many studies focused on its isothermal adsorption, the relationship between its methane adsorption capacity and structural characteristics has yet been well addressed. The pore structures and methane adsorption of four kinds of type-II kerogens with different maturities and at a varying burial depth are studied using a combined approach of molecular dynamics and grand canonical Monte Carlo simulations. Attributed to the combined effect of temperature, pressure, and the surface structures of kerogen, the methane adsorption capacity varies with the kerogen maturity and the burial depth. A maximum methane adsorption is predicted at the depth of 1–3 km, which agrees with the observations. Meanwhile, a mismatch between the porosity change and the adsorption change of kerogens is noted and then interpreted by the surface structure evolution of kerogens. Analysis on the amorphous kerogens reveals that the surface and bulk compositions of kerogens are different, and the difference varies with the kerogen maturity. Methane adsorption depends not only on the porosity but also on the proportion of aromatic and aliphatic carbon atoms on the surface. The simulations are expected to be useful for the reserve prediction and interpretation of shale gas formations.

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Section: Introductionmentioning

confidence: 99%

Gas Adsorption Capacity of Type-II Kerogen at a Varying Burial Depth

Wen

Zhang

et al. 2022

Energy Fuels

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“…Therefore, the micropore filling theory can better characterize the adsorption behavior of CO 2 in shale. 40–42…”

Section: Resultsmentioning

confidence: 99%

Adsorption behavior and mechanism of CO₂in the Longmaxi shale gas reservoir

et al. 2022

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“…The multifractal theory, an extension of monofractal theory, is a powerful tool to finely characterize the pore structure heterogeneity of sedimentary rocks. The multifractal nature of the pore structure in shale reservoirs has been revealed by previous studies. − …”

Section: Introductionmentioning

confidence: 89%

Characterization of an Angstrom-Scale Pore Structure in Organic-Rich Shales by Using Low-Pressure CO₂ Adsorption and Multifractal Theory and Its Role in CH₄/CO₂ Gas Storage

Zhang

et al. 2022

Energy Fuels

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Knowledge of CH 4 and CO 2 storage in pore systems of organic-rich shale can provide valuable perspectives on gasbearing properties and CO 2 sequestration in shale reservoirs. To finely characterize the angstrom-scale pores and investigate their role in CH 4 /CO 2 storage behaviors, this study examines 14 Lower Cambrian Niutitang shale samples by using an array of experiments, including total organic carbon (TOC) content tests, optical observations, section analysis, X-ray diffraction analysis, fieldemission scanning electron microscopy (FE-SEM), low-pressure CO 2 adsorption (LPGA-CO 2 ), and isothermal adsorption experiments. FE-SEM images reveal the presence of three main types of pores in the studied samples: intraparticle organic pores, dissolved intrapores within quartz particles, and intercrystal pores of clay minerals. Furthermore, the pore size distribution (PSD) curves from LPGA-CO 2 possess two prominent peaks, and the pore structure parameters show significant linear covariations with the TOC, clay, quartz, and dolomite contents. The pore structure information exhibits multifractal behavior, and the Q-type cluster analysis on generalized fractal dimension spectrum parameters reveals two distinct types of samples. Type I samples have a stronger degree of PSD heterogeneity, whereas type II samples have better pore connectivity. By virtue of the spherical pore and conceptual pore-filling models, we demonstrate that CO 2 has a higher storage volume in the angstrom scale than CH 4 , whereas CH 4 has a higher ratio of the filling volume to the maximum adsorbed capacity. The filling capacity of CO 2 is 1.121−2.087 (an average of 1.473) times that of CH 4 . From the perspective of pore multifractality, higher pore heterogeneity results in stronger CH 4 and CO 2 storage capacities. The gas filling density in subnano-scale micropores changes with varying pore sizes, which differs from a constant value of the adsorbed gas density for mono-/multilayer adsorption in mesopores. Our findings can provide new geometrical constraints on gas storage behavior in shale reservoirs, which contributes to understanding the gas storage capacity and adsorbed-phase gas density.

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Pore structure heterogeneity of Wufeng-Longmaxi shale, Sichuan Basin, China: Evidence from gas physisorption and multifractal geometries

Cited by 78 publications

References 51 publications

Gas Adsorption Capacity of Type-II Kerogen at a Varying Burial Depth

Gas Adsorption Capacity of Type-II Kerogen at a Varying Burial Depth

Adsorption behavior and mechanism of CO₂in the Longmaxi shale gas reservoir

Characterization of an Angstrom-Scale Pore Structure in Organic-Rich Shales by Using Low-Pressure CO₂ Adsorption and Multifractal Theory and Its Role in CH₄/CO₂ Gas Storage

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Pore structure heterogeneity of Wufeng-Longmaxi shale, Sichuan Basin, China: Evidence from gas physisorption and multifractal geometries

Cited by 78 publications

References 51 publications

Gas Adsorption Capacity of Type-II Kerogen at a Varying Burial Depth

Gas Adsorption Capacity of Type-II Kerogen at a Varying Burial Depth

Adsorption behavior and mechanism of CO2in the Longmaxi shale gas reservoir

Characterization of an Angstrom-Scale Pore Structure in Organic-Rich Shales by Using Low-Pressure CO2 Adsorption and Multifractal Theory and Its Role in CH4/CO2 Gas Storage

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Adsorption behavior and mechanism of CO₂in the Longmaxi shale gas reservoir

Characterization of an Angstrom-Scale Pore Structure in Organic-Rich Shales by Using Low-Pressure CO₂ Adsorption and Multifractal Theory and Its Role in CH₄/CO₂ Gas Storage