Insights into the Molecular Competitive Adsorption Mechanism of CH<sub>4</sub>/CO<sub>2</sub> in a Kerogen Matrix in the Presence of Moisture, Salinity, and Ethane

Li, Jiawei; Wang, Yuzhu; Chen, Zhixi; Rahman, Sheik S.

doi:10.1021/acs.langmuir.1c02274

Cited by 25 publications

(22 citation statements)

References 68 publications

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“…These studies ignore the continuous pressure gradient in the direction of displacement and the back-pressure at the pore outlet. In addition, almost all current molecular simulation studies on CO 2 –CH 4 displacement use homogeneous organic or inorganic matter as pore surface materials. ,− In fact, heterogeneous surface pores composed of both organic and inorganic matter are abundant in the reservoir matrix and have a non-negligible influence on the competing adsorption behavior of gases within the pores. , Therefore, a molecular model that better fits the actual site conditions is urgently needed.…”

Section: Introductionmentioning

confidence: 99%

“…It has been found experimentally by the NMR technique that the process of CO 2 gas displacement of CH 4 can be divided into three stages: the initial stage of competitive adsorption, the dominant stage of competitive adsorption, and the attenuated stage of competitive adsorption . Most of the current studies have focused on the gas behavior during the dominant stage of competitive adsorption ,,,− and the recovery, displacement efficiency, and gas separation at the attenuated stage of competitive adsorption. − During the dominant phase of competitive adsorption, Zhang et al found that 0.65–0.7 nm pores exhibited the highest CO 2 selectivity. The pore size corresponding to the maximum methane recovery decreased with increasing pressure, and low temperature is in favor of methane recovery.…”

Section: Introductionmentioning

confidence: 99%

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Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores

et al. 2023

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Studying the CO2–CH4 displacement process is of great importance to understand the CO2-enhanced shale gas recovery technology. However, most studies have focused on the gas behavior in the reservoir during the dominant stage of competitive adsorption after CO2 injection, as well as the shale gas recovery, displacement efficiency, and gas separation after displacement, while less attention has been paid to the gas behavior during the initial period of displacement. A CO2–CH4 displacement model that can provide a continuous pressure gradient in the displacement direction and a stable back-pressure at the pore outlet was developed based on a heterogeneous surface pore. The model was divided into three areas: CO2 injection area, pore area, and back-pressure area. Molecular dynamics simulations were used to study the effects of depressurization exploitation and injection pressure on the displacement behavior at the initial period of the displacement process under different reservoir conditions. It was found that the displacement process always starts from the CH4 reverse flow stage and then experiences the injection pressure action stage and positive displacement stage in sequence. Moreover, the extent of CH4 reverse flow directly affects the system development process and the final displacement efficiency. A small system presorption pressure and a large injection pressure are beneficial to the displacement. It is believed that the reservoir pressure should be dropped to the lowest possible level during depressurization exploitation, and the CO2 injection pressure needs to be selected by considering displacement efficiency, reservoir safety, and economic cost. The CO2 occupies the adsorption sites near graphene faster than that near montmorillonite (MMT) in the direction of displacement, while the CH4 desorption is faster near MMT. Therefore, it cannot be concluded that the displacement process near graphene is ahead of MMT. It is considered that the gas desorption/adsorption behavior near the graphene dominates the displacement process in terms of gas amount, while the fluctuation near MMT with time and injection pressure directly affects the gas adsorption variation in the pore space from the trend.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores

et al. 2023

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“…Such a result, which deserves further investigation to fully understand the role of moisture content as a function of the kerogen type and maturity, suggests that the impact of moisture content is driven by the water/kerogen interactions but also the gas/water interactions and porosity of the kerogen sample. As an interesting extension of these works on the role of moisture content, Li et al 117 also considered the impact of water content and salinity on CO 2 injection in shale to foster methane recovery. Using a molecular model of type II-D kerogen, these authors considered the following thermodynamic conditions: 0−5 wt % moisture, 0−6 mol/L NaCl saline, and 0−5 wt % C 2 H 6 at different temperatures and pressures.…”

Section: Energymentioning

confidence: 99%

“…Several authors also considered the impact of moisture content on the coadsorption of gases, typically, CH 4 /CO 2 mixtures. ,− As illustrated in Figure , using four kerogen molecular models of different maturities, Huang et al investigated the adsorption of CH 4 , CO 2 , and their mixtures in kerogens as a function of moisture content. Upon increasing the moisture content, the CO 2 /CH 4 selectivity was found to increase for the two mature samples and the most immature sample but to decrease for one of the immature sample.…”

Section: Fluid Thermodynamics and Transport In Kerogenmentioning

confidence: 99%

Development of Atomistic Kerogen Models and Their Applications for Gas Adsorption and Diffusion: A Mini-Review

et al. 2023

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With the emergence of shale gas, numerous atomic-scale models of kerogen have been proposed in the literature. These models, which attempt to capture the structure, chemistry, and porosity of kerogens of various types and maturities, are nowadays commonlyif not routinelyused to gain nanoscale insights into the thermodynamics and dynamics of complex and important processes such as hydrocarbon recovery and carbon sequestration. However, modeling such a complex, disordered, and heterogeneous material is a particularly challenging task. It implies that important underlying assumptions and simplifications, which can significantly affect the predicted properties, have to be made when constructing the kerogen models. In this mini review, we discuss the existing atomistic models of kerogen by categorizing them according to the different approaches and assumptions used during their construction. For each type of model, we also describe how the construction strategy can impact the prediction of certain properties. Important work on kerogen interactions with gas and oil, from both the point of view of equilibrium adsorption (including adsorption-induced deformation) and transport, are described. Possible improvements and upscaling strategiesto better account for kerogen in its geological environmentare also discussed.

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“…In addition, CO 2 plays an essential role in agriculture, petroleum exploitation, and shale and coal seam gas extraction. 3 The separation of CO 2 /N 2 from flue gas has always been a hot topic in gas separation. Among various gas separation methods, pressure swing adsorption (PSA) is the most energy saving and cheapest technique.…”

Section: Introductionmentioning

confidence: 99%

Adsorption Equilibrium and Diffusion of CH₄, CO₂, and N₂ in Coal-Based Activated Carbon

et al. 2023

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Coal-based activated carbon is an ideal adsorbent for concentrating CH4 from coalbed methane and recovering CO2 from industrial waste gas. In order to upgrade the environmentally protective preparation technology of coal-based activated carbons and clarify the adsorption equilibrium and diffusion rules of CH4, CO2, and N2 in these materials, we prepared granular activated carbon (GAC) via air oxidation, carbonization, and physical activation using anthracite as the raw material. Also, we measured the adsorption isotherms and adsorption kinetic data of GAC by the gravimetric method and characterized its surface chemical properties. According to the results, GAC had abundant micropore structures with a pore size mainly in the range of 5.0–10.0 Å, and its surface was covered with plentiful oxygen-containing functional groups. The specific pore structure and surface chemical properties could effectively improve the separation and purification effects of GAC on CH4 and CO2. In the temperature range of 278–318 K, the equilibrium separation of CH4/N2 by GAC with a coefficient between 3 and 4 could be achieved. Also, the CO2/CH4 separation coefficient decreased with the increase in temperature but remained around 3. The bivariate Langmuir equation could describe the adsorption behaviors of GAC on CH4/N2, CO2/N2, and CH4/CO2. With the increase in the concentrations of CH4 and CO2 in the gas phase, the difference between the adsorption capacity of CH4 or CO2 and that of N2 became greater. The change of the gas ratio did not affect the characteristics of preferential adsorption of CH4 and CO2. At different temperatures (278, 298, and 318 K), the diffusion coefficients of CH4, N2, and CO2 at various pressure points showed predominately a small variation without an obvious trend. These results demonstrated that the separation of CH4/N2, CO2/N2, and CH4/CO2 by the activated carbon could only rely on the equilibrium separation effect rather than the kinetic effect.

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Insights into the Molecular Competitive Adsorption Mechanism of CH₄/CO₂ in a Kerogen Matrix in the Presence of Moisture, Salinity, and Ethane

Cited by 25 publications

References 68 publications

Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores

Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores

Development of Atomistic Kerogen Models and Their Applications for Gas Adsorption and Diffusion: A Mini-Review

Adsorption Equilibrium and Diffusion of CH₄, CO₂, and N₂ in Coal-Based Activated Carbon

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Insights into the Molecular Competitive Adsorption Mechanism of CH4/CO2 in a Kerogen Matrix in the Presence of Moisture, Salinity, and Ethane

Cited by 25 publications

References 68 publications

Displacement Characteristics of CO2 to CH4 in Heterogeneous Surface Slit Pores

Displacement Characteristics of CO2 to CH4 in Heterogeneous Surface Slit Pores

Development of Atomistic Kerogen Models and Their Applications for Gas Adsorption and Diffusion: A Mini-Review

Adsorption Equilibrium and Diffusion of CH4, CO2, and N2 in Coal-Based Activated Carbon

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Product

Resources

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Insights into the Molecular Competitive Adsorption Mechanism of CH₄/CO₂ in a Kerogen Matrix in the Presence of Moisture, Salinity, and Ethane

Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores

Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores

Adsorption Equilibrium and Diffusion of CH₄, CO₂, and N₂ in Coal-Based Activated Carbon