Molecular investigation on CO₂-CH₄ displacement and kerogen deformation in enhanced shale gas recovery

Wu, Jian; Huang, Pengyu; Maggi, Federico; Shen, Luming

doi:10.1016/j.fuel.2022.123208

Cited by 24 publications

(10 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%

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%

Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores

et al. 2023

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“…The large swelling experienced by the immature kerogen was subsequently shown to lead to an increase in diffusion coefficient with increasing loading at constant reservoir ( P , T ) conditions, , which is the opposite behavior to the commonly observed one for rigid hosts. More recently, a few studies have been reported in which adsorption-induced deformations in kerogen are accounted for via an hybrid method alternating GCMC cycles and short MD simulations in the isothermal–isobaric (NPT) ensemble. − Doing this, the authors simulate an osmotic ensemble that corresponds to unjacketed adsorption conditions where the fluid and host are simultaneously put under thermal, chemical, and mechanical equilibrium. In all these works, significant swelling, of 1–10% under typical geological pressures were observed, even for supposedly mature kerogen. , …”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, common to all the recent hybrid GCMC/MD studies − is the use of the so-called “molecular” kerogen models of Ungerer et al These models, constructed by packing small and identical molecules, accurately reproduce the chemistry of the material and thus the strength of host–guest interactions. However, due to the limited size of their constituents, it is unclear whether they can accurately capture poromechanics, which are governed by the nature and connectivity of the carbon skeleton of the host.…”

Section: Introductionmentioning

confidence: 99%

“…In all these works, significant swelling, of 1−10% under typical geological pressures were observed, even for supposedly mature kerogen. 21,23 While these recent investigations constitute a significant body of progress, many questions remain unanswered regarding adsorption-induced deformations in microporous carbon. First, as pointed out in ref 18, viscoelastic effects can be important for such materials, which clearly question the sampling time used in simulations and the error bars, rarely reported, regarding obtained modulus, adsorption, swelling and diffusion results.…”

Section: ■ Introductionmentioning

confidence: 99%

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Molecular Simulation of Argon Adsorption and Diffusion in a Microporous Carbon with Poroelastic Couplings

et al. 2023

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Neglected for a long time in molecular simulations of fluid adsorption and transport in microporous carbons, adsorption-induced deformations of the matrix have recently been shown to have important effects on both sorption isotherms and diffusion coefficients. Here we investigate in detail the behavior of a recently proposed 3D-connected mature kerogen model, as a generic model of aromatic microporous carbon with atomic H/C ∼ 0.5, in both chemical and mechanical equilibrium with argon at 243 K over an extended pressure range. We show that under these conditions the material exhibits some viscoelasticity, and simulations of hundreds of nanoseconds are required to accurately determine the equilibrium volumes and sorption loadings. We also show that neglecting matrix internal deformations and swelling can lead to underestimations of the loading by up to 19% (swelling only) and 28% (swelling and internal deformations). The volume of the matrix is shown to increase up to about 8% at the largest pressure considered (210 MPa), which induces an increase of about 33% of both pore volume and specific surface area via the creation of additional pores, yet does not significantly change the normalized pore size distribution. Volume swelling is also rationalized by using a well-known linearized microporomechanical model. Finally, we show that self-diffusivity decreases with applied pressure, following an almost perfectly linear evolution with the free volume. Quantitatively, neglecting swelling and internal deformations tends to reduce the computed self-diffusivities.

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“…Molecular dynamics (MD) uses an integration of the equations of motion for the guest-loaded framework as a whole, enabling direct sampling of the flexibility of the material. This coupled GCMC-MD approach has become computationally feasible in recent years and has been employed to model the sorption of various fluids in flexible MOFs, , coal, , silica materials, kerogen, , and polymers. − However, only a few studies investigated the zeolite pore shape and size response to the adsorption process by directly sampling the change in the unit cell size with progressing adsorption. For instance, Balestra et al applied MC/MD simulations to the system of zeolite RHO–water, and Santander et al focused on silicalite adsorption of furfural–water and hydroxymethyl furfural (HMF)–water mixtures.…”

Section: Introductionmentioning

confidence: 99%

Adsorption-Induced Deformation of Zeolites 4A and 13X: Experimental and Molecular Simulation Study

et al. 2023

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Gas adsorption in zeolites leads to adsorption-induced deformation, which can significantly affect the adsorption and diffusive properties of the system. In this study, we conducted both experimental investigations and molecular simulations to understand the deformation of zeolites 13X and 4A during carbon dioxide adsorption at 273 K. To measure the sample’s adsorption isotherm and strain simultaneously, we used a commercial sorption instrument with a custom-made sample holder equipped with a dilatometer. Our experimental data showed that while the zeolites 13X and 4A exhibited similar adsorption isotherms, their strain isotherms differed significantly. To gain more insight into the adsorption process and adsorption-induced deformation of these zeolites, we employed coupled Monte Carlo and molecular dynamics simulations with atomistically detailed models of the frameworks. Our modeling results were consistent with the experimental data and helped us identify the reasons behind the different deformation behaviors of the considered structures. Our study also revealed the sensitivity of the strain isotherm of zeolites to pore size and other structural and energetic features, suggesting that measuring adsorption-induced deformation could serve as a complementary method for material characterization and provide guidelines for related technical applications.

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Molecular investigation on CO₂-CH₄ displacement and kerogen deformation in enhanced shale gas recovery

Cited by 24 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

Molecular Simulation of Argon Adsorption and Diffusion in a Microporous Carbon with Poroelastic Couplings

Adsorption-Induced Deformation of Zeolites 4A and 13X: Experimental and Molecular Simulation Study

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Molecular investigation on CO₂-CH₄ displacement and kerogen deformation in enhanced shale gas recovery

Cited by 24 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

Molecular Simulation of Argon Adsorption and Diffusion in a Microporous Carbon with Poroelastic Couplings

Adsorption-Induced Deformation of Zeolites 4A and 13X: Experimental and Molecular Simulation Study

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Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores

Displacement Characteristics of CO₂ to CH₄ in Heterogeneous Surface Slit Pores