Modeling Phase Behavior of Nano-Confined Fluids in Shale Reservoirs with A Modified Soave-Redlich-Kwong Equation of State

AbstractThe thermodynamics of fluids in confined (capillary) media is different from the bulk conditions due to the effects of the surface tension, wettability, and pore radius as described by the classical Kelvin equation. This study provides experimental data showing the deviation of propane vapour pressures in capillary media from the bulk conditions. Comparisons were also made with the vapour pressures calculated by the Peng–Robinson equation-of-state (PR-EOS). While the propane vapour pressures measured using synthetic capillary medium models (Hele–Shaw cells and microfluidic chips) were comparable with those measured at bulk conditions, the measured vapour pressures in the rock samples (sandstone, limestone, tight sandstone, and shale) were 15% (on average) less than those modelled by PR-EOS.

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Phase equilibrium modeling for interfacial tension of confined fluids in nanopores using an association equation of state

The Journal of Supercritical Fluids ◽

10.1016/j.supflu.2021.105322 ◽

2021 ◽

pp. 105322

Author(s):

Yu-Long Zhao ◽

Wei Xiong ◽

Lie-Hui Zhang ◽

Jian-Hua Qin ◽

Shi-lin Huang ◽

...

Keyword(s):

Phase Equilibrium ◽

Equation Of State ◽

Interfacial Tension ◽

Confined Fluids ◽

Equilibrium Modeling

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Pore-Scale Simulation of Confined Phase Behavior with Pore Size Distribution and Its Effects on Shale Oil Production

Energies ◽

10.3390/en14051315 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1315

Author(s):

Jingwei Huang ◽

Hongsheng Wang

Keyword(s):

Phase Equilibrium ◽

Equation Of State ◽

Pore Size Distribution ◽

Phase Behavior ◽

Pore Size ◽

Size Distribution ◽

Critical Role ◽

Shale Oil ◽

Pore Scale ◽

Modified Equation

Confined phase behavior plays a critical role in predicting production from shale reservoirs. In this work, a pseudo-potential lattice Boltzmann method is applied to directly model the phase equilibrium of fluids in nanopores. First, vapor-liquid equilibrium is simulated by capturing the sudden jump on simulated adsorption isotherms in a capillary tube. In addition, effect of pore size distribution on phase equilibrium is evaluated by using a bundle of capillary tubes of various sizes. Simulated coexistence curves indicate that an effective pore size can be used to account for the effects of pore size distribution on confined phase behavior. With simulated coexistence curves from pore-scale simulation, a modified equation of state is built and applied to model the thermodynamic phase diagram of shale oil. Shifted critical properties and suppressed bubble points are observed when effects of confinement is considered. The compositional simulation shows that both predicted oil and gas production will be higher if the modified equation of state is implemented. Results are compared with those using methods of capillary pressure and critical shift.

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