A novel pore-size-dependent equation of state for modeling fluid phase behavior in nanopores

Luo, Sheng; Jin, Bikai; Lutkenhaus, Jodie L.; Nasrabadi, Hadi

doi:10.1016/j.fluid.2019.06.009

Cited by 29 publications

(14 citation statements)

References 51 publications

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“…The radius of pore-throat in the shale reservoir is mostly in the range of 1 to 100 nm, which leads to spatial confinement . The confinement effect on fluid property and transport can be attributed to two aspects: capillary pressure between liquid and gas phases, and fluid-wall interaction (i.e., fluid adsorption). , Many publications have sprung up discussing the confinement effect on phase behavior of confined fluid. − On the basis of experimental studies such as nanochannel chip and differential scanning calorimetry, some scholars have observed that the critical temperature and pressure of hydrocarbons are lower in nanopores than in the bulk phase, and the difference increases gradually with the decrease of pore size . However, due to the unconventional features of shale formation and the limitations of devices (the challenge of building nanofluidic chips or high-quality nanoscale porous media models), the experimental studies on the phase behavior of shale nanopores are difficult and the accuracy of the data is uncertain .…”

Section: Introductionmentioning

confidence: 99%

“…Hence, some recent studies focus on developing EOS that can describe the effects of confinement. , Zhang et al modified the van der Waals equation of state (vdW-EOS) by considering the effects of molecule–molecule interactions and pore size. Luo et al extended the Peng–Robinson equation of state (PR-EOS) with a fluid–pore wall interaction energy parameter to predict the transition temperatures under different pore diameters. Song et al developed a novel fluid adsorption characterization method and then presented an adsorption-dependent PR-EOS (A-PR-EOS) to study the relationship between fluid adsorption and its induced critical property shift of pure components.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Nanopore Confinement on Fluid Phase Behavior and Production Performance in Shale Oil Reservoir

Song

Guo

et al. 2021

Ind. Eng. Chem. Res.

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The confinement effects including capillarity and adsorption play a significant role in phase behavior and transport of shale fluids. The effect of capillary pressure has been widely studied and is fully understood. However, the investigation of the adsorption effect on reservoir fluid properties and production performance is still lacking. In this work, an efficient model is proposed to fill this gap and investigate the phase behavior and well performance in the Bakken shale oil reservoir. First, an improved phase equilibrium model is developed based on an adsorption-dependent Peng−Robinson equation of state and a modified Young−Laplace equation. The effect of adsorption and adsorption induced critical property shifts in nature is considered. Second, the phase equilibrium model is used to calculate and compare the black-oil properties of the Bakken oil under different pressures and confinement conditions. Finally, the fluid properties results are combined with the reservoir simulator to assess the confinement effects on the well performance of the Bakken shale reservoir. The result indicates that fluid adsorption makes a more significant contribution to the suppressed bubble point pressure than capillarity. The change in the black-oil properties shows that the confinement effect exhibits a great impact on the physical properties of the oil phase including solution gas−oil ratio, oil formation volume factor, and oil viscosity, but presents a small impact on the physical properties of the gas phase including gas formation volume factor and gas viscosity. In terms of production performance, the presence of confinement increases the cumulative oil production, first increasing, and then decreasing cumulative gas production, which leads to a flatter producing gas−oil ratio. Overall, the effect of adsorption is more significant under high-pressure conditions, and the effect of capillary pressure is more significant under low-pressure conditions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Nanopore Confinement on Fluid Phase Behavior and Production Performance in Shale Oil Reservoir

Song

Guo

et al. 2021

Ind. Eng. Chem. Res.

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“…When the system scale is reduced to the micro/nano level, the fluid behavior becomes size dependent with the enhancement of confinement effect, and the thermodynamic properties and phase equilibrium of the confined fluids are substantially changed . Many scholars from different disciplines agree that fluid confinement may change apparent physical properties, such as critical pressure and temperature, density, viscosity, surface tension, and freezing and melting temperatures. − However, the trend of many physical properties shifts is still unclear, and some conflicting results occur in the predicted behavior of fluids in nanopores. For example, most of the studies suggest that confinement results in a decrease in bubble point pressure, but the change in dew point pressure is somewhat controversial. − …”

Section: Introductionmentioning

confidence: 99%

Phase Behavior of Hydrocarbon Mixture in Shale Nanopores Considering the Effect of Adsorption and Its Induced Critical Shifts^☆

Song

Feng

et al. 2020

Ind. Eng. Chem. Res.

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Phase behavior of shale gas or oil in nanopores is not yet well understood. One complexity comes from the fact that fluid adsorption can be significant in densely developed nanopores. A prediction process for the behavior of a ternary mixture (CH 4 , n-C 4 H 10 , and n-C 8 H 18 ) and an actual Bakken oil in nanopore formation are performed by applying an adsorption-dependent Peng− Robinson equation of state, and the effect of adsorption and its induced critical properties shifts is discussed. Results indicate that the presence of adsorption could decrease the vapor−liquid equilibrium coefficient (K-value) and the vapor phase molar fraction for the confined ternary mixture, especially in the nanopores with a few nanometers. The shift in the saturation pressures of the ternary mixture and Bakken oil shows that the bubble point pressure and upper dew point pressure are depressed and the lower dew point pressure is increased with the synthetic effect of adsorption and critical shifts. The suppressed bubble point pressure well explains the production performance of a long-term flat producing gas/oil ratio in the Bakken reservoir. It should be noted that adsorption is relatively more dominant on bubble point pressure and critical shifts exhibit a greater influence on dew point pressure. For Bakken oil, the presence of adsorption increases the oil density and viscosity; however, critical shifts present conflicting impacts on oil density and viscosity, and the critical shifts are more dominant compared with fluid adsorption. This emphasizes the importance of considering both adsorption and critical shifts when describing phase behavior in shale nanopores.

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“…Except for the above experimental studies, molecular simulation is also introduced in this area (Nojabaei et al, 2013;Dong et al, 2016;Luo et al, 2019) together with density functional theory (also known as DFT) (Barbosa et al, 2016) and much more interesting and useful insights have been gathered in these theoretical and numerical studies. The classical Lennard-Jones potential is selected in the grand canonical Monte Carlo (also known as GCMC) simulation and the phase transition mechanisms in the fluid structures inside the confining geometry has been analyzed in (Thommes et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Phase equilibrium calculations in shale gas reservoirs

Zhang

Sun

2019

Capillarity

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Compositional multiphase flow in subsurface porous media is becoming increasingly attractive due to issues related with enhanced oil recovery, CO 2 sequestration and the urgent need for development in unconventional oil/gas reservoirs. One key effort to construct the mathematical model governing the compositional flow is to determine the phase compositions of the fluid mixture, and then calculate other related physical properties. In this paper, recent progress on phase equilibrium calculations in unconventional reservoirs has been reviewed and concluded with authors' own analysis, especially focusing on the special mechanisms involved. Phase equilibrium calculation is the main approach to investigate phase behaviors, which could be conducted using different variable specifications, such as the NPT flash and NVT flash. Recently, diffuse interface models, which have been proved to possess a high consistency with thermodynamic laws, have been introduced in the phase equilibrium calculation, incorporating the realistic equation of state (EOS), e.g. Peng-Robinson EOS. In the NVT flash, the Helmholtz free energy is minimized instead of the Gibbs free energy used in NPT flash, and this thermodynamic state function is decomposed into two terms using the convex-concave splitting technique. A semi-implicit numerical scheme is applied to the dynamic model, which ensures the thermodynamic stability and then preserves the fast convergence property. A positive definite coefficient matrix is designed to meet the Onsager reciprocal principle so as to keep the entropy increasing property in the presence of capillary pressure, which is required by the second law of thermodynamics. The robustness of the proposed algorithm is demonstrated by using two numerical examples, one of which has up to seven components. In the complex fluid mixture, special phenomena could be captured from the global minimum of tangent plane distance functions and the phase envelope. It can be found that the boundary between the single-phase and vapor-liquid two phase regions shifts in the presence of capillary pressure, and then the area of each region changes accordingly. Furthermore, the effect of the nanopore size distribution on the phase behavior has been analyzed and a multi-scale scheme is presented based on literature reviews. Fluid properties including swelling factor, criticality, bubble point and volumetrics have been investigated thoroughly by comparing with the bulk fluid flow in a free channel.

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A novel pore-size-dependent equation of state for modeling fluid phase behavior in nanopores

Cited by 29 publications

References 51 publications

Effect of Nanopore Confinement on Fluid Phase Behavior and Production Performance in Shale Oil Reservoir

Effect of Nanopore Confinement on Fluid Phase Behavior and Production Performance in Shale Oil Reservoir

Phase Behavior of Hydrocarbon Mixture in Shale Nanopores Considering the Effect of Adsorption and Its Induced Critical Shifts^☆

Phase equilibrium calculations in shale gas reservoirs

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A novel pore-size-dependent equation of state for modeling fluid phase behavior in nanopores

Cited by 29 publications

References 51 publications

Effect of Nanopore Confinement on Fluid Phase Behavior and Production Performance in Shale Oil Reservoir

Effect of Nanopore Confinement on Fluid Phase Behavior and Production Performance in Shale Oil Reservoir

Phase Behavior of Hydrocarbon Mixture in Shale Nanopores Considering the Effect of Adsorption and Its Induced Critical Shifts☆

Phase equilibrium calculations in shale gas reservoirs

Contact Info

Product

Resources

About

Phase Behavior of Hydrocarbon Mixture in Shale Nanopores Considering the Effect of Adsorption and Its Induced Critical Shifts^☆