Phase Envelope Calculations for Reservoir Fluids in the Presence of Capillary Pressure

Lemus, Diego Rolando Sandoval; Yan, Wei; Michelsen, Michael Locht; Stenby, Erling Halfdan

doi:10.2118/175110-ms

Cited by 28 publications

(9 citation statements)

References 12 publications

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“…Major efforts have been from theoretical works, which can study mechanisms of the phase behavior of confined hydrocarbons at the nanoscale. A common approach is to couple the capillary pressure model with the EOS modeling, ,,− assuming homogeneous density distributions and ignoring fluid–surface interactions. This approach has been coupled into reservoir simulators to model shale well productivity .…”

Section: Introductionmentioning

confidence: 99%

Bubble Point Pressures of Hydrocarbon Mixtures in Multiscale Volumes from Density Functional Theory

et al. 2018

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Accurate characterization of the bubble point pressure of hydrocarbon mixtures under nanoconfinement is crucial to the prediction of ultimate oil recovery and well productivity of shale/tight oil reservoirs. Unlike conventional reservoirs, shale has an extensive network of tiny pores in the range of a few nanometers. In nanopores, the properties of hydrocarbon fluids deviate from those in bulk because of significant surface adsorption. Many previous theoretical works use a conventional equation of state model coupled with capillary pressure to study the nanoconfinement effect. Without including the inhomogeneous molecular density distributions in nanoconfinement, these previous approaches predict only slightly reduced bubble points. In this work, we use density functional theory to study the effect of nanoconfinement on the hydrocarbon mixture bubble point pressure by explicitly considering fluid−surface interactions and inhomogeneous density distributions in nanopores. We find that as system pressure decreases, while lighter components are continuously released from the nanopores, heavier components accumulate within. The bubble point pressure of nanoconfined hydrocarbon mixtures is thus significantly suppressed from the bulk bubble point to below the bulk dew point, in line with our previous experiments. When bulk fluids are in a two-phase, the confined hydrocarbon fluids are in a single liquid-like phase. As pore size increases, bubble point pressure of confined fluids increases and hydrocarbon average density in nanopores approaches the liquid-phase density in bulk when bulk is in a two-phase region. For a finite volume bulk bath, we find that because of the competitive adsorption in nanopores, the bulk bubble point pressure increases in line with a previous experimental work. Our work demonstrates how mixture dynamics and nanopore−bulk partitioning influence phase behavior in nanoconfinement and enables the accurate estimation of hydrocarbon mixture bubble point pressure in shale nanopores.

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Section: Introductionmentioning

confidence: 99%

Bubble Point Pressures of Hydrocarbon Mixtures in Multiscale Volumes from Density Functional Theory

et al. 2018

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“…These three factors significantly impact the phase behavior of confined fluids in nanopores. Previously, some studies have investigated the effect of capillary pressure on the phase behavior of reservoir fluids in confined space, but the adsorption behavior of confined fluids was neglected. − In this paper, we systemically investigate the influence of capillary pressure, a critical shift and adsorption behavior on the phase behavior of confined fluids in nanopores.…”

Section: Introductionmentioning

confidence: 99%

Phase Equilibria of Confined Fluids in Nanopores of Tight and Shale Rocks Considering the Effect of Capillary Pressure and Adsorption Film

Dong

Liu

Hou

et al. 2016

Ind. Eng. Chem. Res.

162

109

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Because of the effect of nanoscale confinement, the phase behavior of fluids confined in nanopores differs significantly from that observed in a PVT cell. In this paper, the cubic Peng–Robinson equation of state (EOS) is coupled with capillary pressure equation and adsorption theory to investigate and represent the phase equilibria of pure components and their mixtures in cylindrical nanopores. The shift of critical properties is also taken into account. Because of the effect of an adsorption film, an improved Young–Laplace equation is adopted to simulate capillarity instead of the conventional equation. For the adsorption behavior, the experimental data of the adsorbent of silicalite are used to represent the adsorption behavior of hydrocarbons in nanopores. Then a prediction process for the behavior of methane, n-butane, n-pentane, n-hexane and their mixtures are performed. Furthermore, the results are compared against the available experimental data to validate the accuracy of this scheme. An actual Eagle Ford oil is also used to examine the performance of our scheme. Results indicate that the presence of an adsorption film can further increase the vapor–liquid equilibrium constant (K-value) and capillary pressure of the confined pure-component fluid, especially in the nanopores with a few nanometers. The smaller the nanopore radius, the higher the deviation between the actual K-value and the estimated value. The capillary pressure presents a bilinear relationship with the pore radius in a log–log plot. For a binary mixture, it is observed the higher the difference between the two components, the stronger the nanopore confinement effects. For a multicomponent mixture and the real Eagle Ford oil, as the pore radius reduces, the bubble point pressure is depressed and the dew point pressure is increased. When the adsorption film is neglected, the bubble point pressure is overestimated, and the dew point pressure is underestimated. For the Eagle Ford oil, when the nanopore radius is higher than about 100 nm, the behavior approaches the bulk value and the influence of nanopore confinement can be neglected. The depression of bubble point pressure of an Eagle Ford oil reservoir well explains the behavior of a long-lasting flat producing gas/oil ratio (GOR). The phase behavior of tight oil plays an important role in reserve evaluation and development process of tight oil reservoirs. This study will shed some important insights on the phase behavior of tight oil in nanopores.

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“…4 does not con- sider the presence of capillary pressure introduced by the curved interface. When capillary pressure is present, phase-envelope locations will change, especially at conditions away from the critical point [23,24].…”

Section: Two-component Hydrocarbon Mixturementioning

confidence: 99%

A thermodynamically consistent pseudo-potential lattice Boltzmann model for multi-component, multiphase, partially miscible mixtures

Peng

Ayala

2019

Preprint

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Current multi-component, multiphase pseudo-potential lattice Boltzmann models have thermodynamic inconsistencies that prevent them to correctly predict the phase behaviors of miscible multi-component mixtures, such as hydrocarbon mixtures. This paper identifies these inconsistencies and attempts to design a thermodynamically consistent multi-component, multiphase pseudo-potential lattice Boltzmann model that allows mass transfer across the phase interfaces and is capable to predict the phase behavior of typically miscible hydrocarbon mixtures. The designed model qualitatively predicts the phase behavior of hydrocarbon mixtures, and shows that achieving precise thermodynamic consistency requires enforcing the more general iso-fugacity rule, which is also briefly discussed.

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Phase Envelope Calculations for Reservoir Fluids in the Presence of Capillary Pressure

Cited by 28 publications

References 12 publications

Bubble Point Pressures of Hydrocarbon Mixtures in Multiscale Volumes from Density Functional Theory

Bubble Point Pressures of Hydrocarbon Mixtures in Multiscale Volumes from Density Functional Theory

Phase Equilibria of Confined Fluids in Nanopores of Tight and Shale Rocks Considering the Effect of Capillary Pressure and Adsorption Film

A thermodynamically consistent pseudo-potential lattice Boltzmann model for multi-component, multiphase, partially miscible mixtures

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