Molecular insight into replacement dynamics of CO2 enhanced oil recovery in nanopores

Wang, Runxi; Bi, Sheng; Guo, Zhaoli; Feng, Guang

doi:10.1016/j.cej.2022.135796

Cited by 31 publications

(13 citation statements)

References 41 publications

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“…The displacement efficiency can be reinforced with the increase of chain length and viscoelasticity . There are also some studies on the gas replacement of oil molecules in blind pores. , The carbon dioxide and methane show two different exchange modes for the extraction of decane molecules in calcite pores. The former preferentially exchanges the adsorbed decane molecules and then it turns to free decane molecules, while the latter shows an opposite exchange transition .…”

Section: Introductionmentioning

confidence: 99%

Molecular Understanding on Migration and Recovery of Shale Gas/Oil Mixture through a Pore Throat

Hong

et al. 2022

Energy Fuels

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Shale gas/oil remaining in blind pores accounts for a large proportion in total reserves, which is urgent to be further exploited. Understanding the microscopic mechanism of gas/oil extraction from blind pores is critical to enhanced gas/oil recovery. In this study, we investigated the migration and recovery behavior of shale gas/oil mixture through a pore throat connecting blind pores and microfractures. Our simulations show that some oil molecules tend to migrate in the form of clusters, which increases their effective size and causes possible blockage of the pore throat. The recovery ratio of gas/ oil mixture has a strong dependence on the pore size. Below the critical size, which is smaller than the size of oil clusters, the pore throat would be blocked and the recovery ratio will decrease significantly. The heavy fractions of shale oil suppress the extraction of gas/oil molecules from blind pores by four inhibition mechanisms: edge adsorption, surface adsorption, throat blockage, and liquid bridge. The kerogen pore shows a stronger adsorption ability for gas/oil mixture than quartz pore, resulting in more residues in it. We also found that a higher gas/oil ratio can provide a larger driven force, leading to a higher recovery of methane and light fractions. These findings advance the understanding of the recovery mechanisms of remaining gas/oil in blind pores and provide a practical guideline on shale gas/oil exploitation.

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Section: Introductionmentioning

confidence: 99%

Molecular Understanding on Migration and Recovery of Shale Gas/Oil Mixture through a Pore Throat

Hong

et al. 2022

Energy Fuels

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“…Recent works , have shown that the steady transport process of hydrocarbons and carbon dioxide within nanopores is diffusion-based. From this finding, here we derive a model that best describes our setup in Figure a by solving the one-dimensional diffusion equation in a single straight nanopore and extend this to a general porous network, which is given by N ( t ) = normalΔ N [ 2 π 2 ∑ n = 0 ∞ exp ( − true( n + 1 2 true) 2 4 t λ 0 L 2 ) true( n + 1 2 true) 2 ] + N̅ where normalΔ N = ( N 0 − N̅ ) is the change in the number of adsorbed gas molecules at time t = 0 (given by N 0 ) and the steady-state (given by N̅ , t → ∞) and L is the length of the kerogen sample in the direction of adsorption. Note N 0 = 0 in all the adsorption cases we present in the manuscript.…”

Section: Methodsmentioning

confidence: 99%

“…Recent works 16,39 have shown that the steady transport process of hydrocarbons and carbon dioxide within nanopores is diffusion-based. From this finding, here we derive a model that best describes our setup in Figure 1a by solving the one-dimensional diffusion equation in a single straight nanopore 40 and extend this to a general porous network, which is given by Ä…”

Section: ■ Introductionmentioning

confidence: 99%

Interfacial Adsorption Kinetics of Methane in Microporous Kerogen

Wang

Datta

et al. 2023

Langmuir

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Rapid declines in unconventional shale production arise from the poorly understood interplay between gas transport and adsorption processes in microporous organic rock. Here, we use highfidelity molecular dynamics (MD) simulations to resolve the timevarying adsorption of methane gas in realistic organic rock samples, known as kerogen. The kerogen samples derive from various geological shale fields with porosities ranging between 20% and 50%. We propose a kinetics sorption model based on a generalized solution of diffusive transport inside a nanopore to describe the adsorption kinetics in kerogen, which gives excellent fits with all our MD results, and we demonstrate it scales with the square of the length of kerogen. The MD adsorption time constants for all samples are compared with a simplified theoretical model, which we derive from the Langmuir isotherm for adsorption capacitance and the freevolume theory for steady, highly confined bulk transport. While the agreement with the MD results is qualitatively very good, it reveals that, in the limit of low porosity, the diffusive transport term dominates the characteristic time scale of adsorption, while the adsorption capacitance becomes important for higher pressures. This work provides the first data set for adsorption kinetics of methane in kerogen, a validated model to accurately describe this process, and a qualitative model that links adsorption capacitance and transport with the adsorption kinetics. Furthermore, this work paves the way to upscale interfacial adsorption processes to the next scale of gas transport simulations in mesopores and macropores of shale reservoirs.

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“…The rescaled MD and experimental data show very good agreement, thus highlighting the power of MD simulations of nanoscopic systems in understanding experimental data. It is worth noting that the diffusive nature of gas recovery facilitated by gas injection is the same as that of oil recovery from nanopores driven by gas injection. − …”

Section: Pore-scale Physics Of Shale Gas Recovery Dynamicsmentioning

confidence: 99%

Review on Pore-Scale Physics of Shale Gas Recovery Dynamics: Insights from Molecular Dynamics Simulations

et al. 2022

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Reliable prediction of gas recovery from shale formations is essential for achieving the full potential of shale gas. A distinguishing feature of shales is that nanoscale pores dominate their porosity. Hence, confinement and fluid−wall interactions modulate shale gas storage, transport, and recovery, which are neglected in conventional gas recovery models. Because these nanoscale effects can be simulated using molecular dynamics (MD), related works have proliferated. Here, we review MD modeling of shale gas recovery at the pore scale. The design and simulation protocols of MD systems for studying gas recovery are surveyed first. Then, the gas recovery in three scenarios, i.e., recovery of single-component gas, recovery of multicomponent gas, and gas recovery involving multiphase flows, are reviewed. In particular, works exploring and elucidating new pore-scale phenomena and guiding and validating new pore-scale continuum models are highlighted. Finally, we recommend best practices in MD shale gas studies and suggest several research directions.

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Molecular insight into replacement dynamics of CO2 enhanced oil recovery in nanopores

Cited by 31 publications

References 41 publications

Molecular Understanding on Migration and Recovery of Shale Gas/Oil Mixture through a Pore Throat

Molecular Understanding on Migration and Recovery of Shale Gas/Oil Mixture through a Pore Throat

Interfacial Adsorption Kinetics of Methane in Microporous Kerogen

Review on Pore-Scale Physics of Shale Gas Recovery Dynamics: Insights from Molecular Dynamics Simulations

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