On the pressure and temperature dependence of adsorption densities and other thermodynamic properties in gas shales

Xiong, Fengyang; Rother, G.; Tomasko, David L.; Pang, Wanying; Moortgat, Joachim

doi:10.1016/j.cej.2020.124989

Cited by 34 publications

(52 citation statements)

References 58 publications

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“…The Ono-Kondo model process several advantages and it was introduced for representing gas adsorption on shale successfully [54][55][56]. The Ono-Kondo model for multilayer adsorption can be expressed as [57]: (12) ln ln 1000 ⋅ n ex = ln ln 1000 ⋅ n abs = + ln P (13) n abs = 1 1000 exp exp where X i is the fraction of occupied adsorption site in the ith layer; X b is the fraction occupied by the bulk phase, and X i+1 = X b ; ρ i is the density of adsorbed phase in the ith layer; ρ m is the maximum density of adsorbed phase, namely, the density when all the adsorption site are occupied; k is the Boltzmann constant; z 0 is coordination number in the bulk; z 1 is coordination number within any layer; z 2 = (z 0 -z 1 )/2.…”

Section: Evaluation Of the Absolute From The Excess Adsorptionmentioning

confidence: 99%

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Absolute adsorption and adsorbed volume modeling for supercritical methane adsorption on shale

Mischo

2022

Adsorption

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Adsorbed methane significantly affects shale gas reservoir estimates and shale gas transport in shale formations. Hence, a practical model for accurately representing methane adsorption behavior at high-pressure and high-temperature in shale is imperative. In this study, a reliable mathematical framework that estimates the absolute adsorption directly from low-pressure excess adsorption data is applied to describe the excess methane adsorption data in literature. This method provides detailed information on the volume and density of adsorbed methane. The obtained results indicate that the extensively used supercritical Dubinin-Radushkevich model with constant adsorbed phase density underestimates absolute adsorption at high pressure. The adsorbed methane volume increases both the pressure and expands with the temperature. The adsorbed methane density reduces above 10 MPa, and approaches a steady value at high pressure. This study provides a novel method for estimating adsorbed shale gas, which is expected improve the prediction of shale gas in place and gas production.

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Section: Evaluation Of the Absolute From The Excess Adsorptionmentioning

confidence: 99%

“…Recent investigation by applying the Ono-Kondo model have showed that the supercritical methane adsorption on shale is monolayer adsorption [56]. In this study, we apply the monolayer scenario of the Ono-Kondo model to represent the experimental data.…”

Section: Evaluation Of the Absolute From The Excess Adsorptionmentioning

confidence: 99%

Absolute adsorption and adsorbed volume modeling for supercritical methane adsorption on shale

Mischo

2022

Adsorption

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“…The adsorption configuration diagram demonstrates a clear adsorption layer on the organic wall. Besides, the adsorption pattern of different components of the fluid on the organic wall is different, reflecting that CO 2 has different abilities to displace various types of alkanes [24,25]. A large number of long-chain n-alkanes were adsorbed on the graphene wall, such as CO 2 and n-butane.…”

Section: Study Of Competitive Adsorption Patternsmentioning

confidence: 99%

Research on Organic Nanopore Adsorption Mechanism and Influencing Factors of Shale Oil Reservoirs

Dou

et al. 2021

Geofluids

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The adsorption properties of shale oil are of great significance to the development of shale oil resources. This study is aimed at understanding the microscopic adsorption mechanism of shale oil in organic nanopores. Thus, a molecular model of organic micropore walls and multicomponent fluids of CO2, C4H10, C8H18, and C12H26 is constructed to investigate the adsorption pattern of multicomponent fluids in organic nanopores under different temperature and pore size conditions. The quantity and heat of adsorption are simulated with the Monte Carlo method, which has been used in previous studies for single-or two-component fluids. The results demonstrate that the ability of CO2 to displace various alkanes is different. Specifically, medium-chain n-alkanes are slightly weaker than light alkanes in competitive sorption, and long-chain n-alkanes are less conducive to competitive sorption. The higher the CO2 sorption ratio, the more the sorption sites occupied by CO2. Thus, it is the best replacement for shale oil. The adsorption quantity of carbon dioxide, n-butane, and n-octane in organic nanopores first increases and then decreases as temperature rises. Meanwhile, the adsorption quantity of n-dodecane decreases firstly and then increases. With the increase in the pore size, the adsorption quantity of carbon dioxide, n-butane, and n-octane in organic nanopores increases while the adsorption quantity of n-dodecane first increases and then decreases. Besides, the model with larger pore sizes is more sensitive to pressure changes in the adsorption of carbon dioxide and n-butane than the model with smaller pore sizes. The heat of adsorption is CO2, C12H26, C8H18, and C4H10 in descending order. All are physical adsorption. Moreover, the adsorption quantity of all four components mixed fluid in the organic matter nanopores is positively correlated with the heat of adsorption.

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“…However, this kind of assumption is currently only carried out in molecular simulations. ,,, Although a lot of previous studies ,,,,,− approximated the volume of micropores (pore size of <2 nm) in the shale to the adsorbed phase volume, the reliability of this kind of assumption to the adsorbed phase volume still cannot be verified. In some studies, the absolute adsorption divided by a fixed adsorbed volume can recover the adsorbed phase density as a function of the pressure, but the absolute adsorption is still obtained by the fixed density model; obviously, the recovery is unreasonable. ,, As in the latest study by Xiong et al, the fixed density isotherm adsorption model (Langmuir model and Ono–Kondo model) was used to fit the excess adsorption isotherm to obtain the absolute adsorption capacity and the absolute adsorption capacity divided by a fixed adsorbed phase volume to obtain the adsorbed phase density as a function of the pressure. Obviously, this operation is turning the cart before the horse, and the adsorbed phase density obtained by this way is inaccurate and inconvenient.…”

Section: Introductionmentioning

confidence: 99%

Improved Methane Adsorption Model in Shale by Considering Variable Adsorbed Phase Density

Kong¹,

Fan²,

Xiao

et al. 2021

Energy Fuels

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Numerous models have been used to describe the isotherm adsorption of supercritical methane in porous media. Many models assume that the adsorbed phase density does not change with pressure during the adsorption process. However, recent studies show that this assumption is unreasonable, and the resulting error is enormous. Therefore, we propose an improved isotherm adsorption model in shale that assumes that the adsorbed phase density keeps changing and that adsorbed phase volume remains constant during the adsorption process [the variable density adsorption (VD) model]. A logarithmic function is used to describe the change of the adsorbed phase density during the adsorption process. The product of the adsorbed phase density and volume is used to calculate the adsorption capacity. The fitting results for large amounts of methane adsorption data show that this assumption is reasonable. The fitting results are consistent with the molecular simulation, and it will be more convenient to obtain the truly adsorbed phase volume and density. The adsorbed phase volume and density obtained by the VD model show a good positive correlation with the total organic carbon, specific surface area, and micropore volume, which indicates the rationality of adsorption parameters fitted by the model. As a result of the correct calculation of the adsorption phase density, the gas in place (GIP) obtained by the VD model is lower than the supercritical Dubinin–Radushkevich model. The new model proposed this time provides a new tool for the study of shale methane isotherm adsorption and a new model for the calculation of GIP. Using this model, the adsorbed phase density and volume of methane can be obtained more conveniently and accurately. This will be a milestone in the VD model.

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On the pressure and temperature dependence of adsorption densities and other thermodynamic properties in gas shales

Cited by 34 publications

References 58 publications

Absolute adsorption and adsorbed volume modeling for supercritical methane adsorption on shale

Absolute adsorption and adsorbed volume modeling for supercritical methane adsorption on shale

Research on Organic Nanopore Adsorption Mechanism and Influencing Factors of Shale Oil Reservoirs

Improved Methane Adsorption Model in Shale by Considering Variable Adsorbed Phase Density

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