Using Capillary Condensation and Evaporation Isotherms to Investigate Confined Fluid Phase Behavior in Shales

The abundance of nanopores (pores with diameters between 2 and 100 nm) in shale and ultra-tight reservoirs precludes the use of common pressure-volume-temperature (PVT) analyses on reservoir fluids. The small sizes of the pores cause capillary condensation, which is a nanoconfinement-induced gas-to-liquid phase change, that can occur at pressures more than 50% below the corresponding bulk phase change of the fluid due to strong fluid-pore wall interactions. We quantify this phenomenon by measuring propane isotherms both in a synthetic nanoporous medium and a core from a shale gas reservoir. Comparison of our results in the two porous media indicates the occurrence of capillary condensation in shale rock. At the same time, we observe capillary condensation hysteresis for shale, in which the density of the fluid is significantly lighter during desorption than adsorption. This indicates structural changes to the rock matrix caused by the phase behavior of the confined fluid. We use scanning electron microscopy to corroborate our findings. These results have significant implications for determining the PVT properties, porosity, and permeability of shale and ultra-tight formations for use in reservoir modeling and production estimations.

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Determination of Confined Fluid Phase Behavior Using Modified Peng-Robinson Equation of State

Proceedings of the 6th Unconventional Resources Technology Conference ◽

10.15530/urtec-2018-2903084 ◽

2018 ◽

Cited By ~ 3

Author(s):

Gang Yang ◽

Zhaoqi Fan ◽

Xiaoli Li

Keyword(s):

Equation Of State ◽

Phase Behavior ◽

Fluid Phase ◽

Confined Fluid ◽

Robinson Equation

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Determination of confined fluid phase behavior using extended Peng-Robinson equation of state

Chemical Engineering Journal ◽

10.1016/j.cej.2019.122032 ◽

2019 ◽

Vol 378 ◽

pp. 122032 ◽

Cited By ~ 11

Author(s):

Gang Yang ◽

Zhaoqi Fan ◽

Xiaoli Li

Keyword(s):

Equation Of State ◽

Phase Behavior ◽

Fluid Phase ◽

Confined Fluid ◽

Robinson Equation

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Minimum Miscibility Pressure of Gas Injection in Unconventional Reservoirs

10.2118/208625-stu ◽

2021 ◽

Author(s):

Gang Yang

Keyword(s):

Phase Behavior ◽

Gas Injection ◽

Fluid Phase ◽

Unconventional Reservoirs ◽

Unconventional Reservoir ◽

Minimum Miscibility Pressure ◽

Confined Fluid ◽

Miscible Gas Injection ◽

Fluid Characterization ◽

The Impact

Abstract Unconvnetional reservoirs are predominantly consisted of nanoscale pores. The strong confinement effect within nanopores imposes significant deviations to the confined fluid phase behavior. Minimum miscibility pressure (MMP) in unconventional reservoirs, as a parameter highly related to the phase behavior of confined fluids, is inevitably affected by the nanoscale confinement. The objective of this work is to investigate the impact of nanoscale confinement on MMP of unconventional reservoir fluids and to recognize a reliable theoretical approach to determine the MMP values in unconventional reservoirs. A modified Peng-Robinson equation of state (PR EOS) applicable for confined fluid characterization is applied to perform the EOS simulation of the vanishing interfacial tension (VIT) experiments. The MMP of a binary mixture at bulk and 50 nm are obtained via the VIT simulation. Meanwhile, the multiple mixing cell (MMC) algorithm coupled with the modified PR EOS is applied to compute the MMP for the same binary system. Comparison of the calculated results to the experimental values recognize that the MMC approach has higher accuracy in determining the MMP of confined fluid systems. Moreover, this approach is then applied to predict the MMP values of both Bakken and Eagle Ford oil at different pore sizes with various injected gases. Results demonstrate that the nanoscale confinement causes drastic suppression to the MMP of unconventional reservoir fluids and the suppression rate increases with decreasing pore size. The drastic suppression of MMP is highly favorable for the miscible gas injection EOR in unconventional reservoirs.

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The Effect of Topology on Phase Behavior under Confinement

Processes ◽

10.3390/pr9071220 ◽

2021 ◽

Vol 9 (7) ◽

pp. 1220

Author(s):

Arnout M. P. Boelens ◽

Hamdi A. Tchelepi

Keyword(s):

Phase Behavior ◽

Density Functional ◽

Capillary Condensation ◽

Good Description ◽

Functional Theory ◽

Minkowski Functionals ◽

First Order ◽

Lennard Jones ◽

And Topology ◽

First Order Transition

This work studies how morphology (i.e., the shape of a structure) and topology (i.e., how different structures are connected) influence wall adsorption and capillary condensation under tight confinement. Numerical simulations based on classical density functional theory (cDFT) are run for a wide variety of geometries using both hard-sphere and Lennard-Jones fluids. These cDFT computations are compared to results obtained using the Minkowski functionals. It is found that the Minkowski functionals can provide a good description of the behavior of Lennard-Jones fluids down to small system sizes. In addition, through decomposition of the free energy, the Minkowski functionals provide a good framework to better understand what are the dominant contributions to the phase behavior of a system. Lastly, while studying the phase envelope shift as a function of the Minkowski functionals it is found that topology has a different effect depending on whether the phase transition under consideration is a continuous or a discrete (first-order) transition.

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Phase Behavior and Structural Changes in Tetraethylorthosilicate-Derived Gels in the Presence of Polyethylene Glycol, Studied by Rheological Techniques and Visual Observations

Journal of Colloid and Interface Science ◽

10.1006/jcis.1998.5523 ◽

1998 ◽

Vol 204 (1) ◽

pp. 45-52 ◽

Cited By ~ 33

Author(s):

P. Ågren ◽

J.B. Rosenholm

Keyword(s):

Polyethylene Glycol ◽

Phase Behavior ◽

Structural Changes ◽

Visual Observations

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Coupling Analysis of Fluid-Structure Interaction and Flow Erosion of Gas-Solid Flow in Elbow Pipe

Advances in Mechanical Engineering ◽

10.1155/2014/815945 ◽

2014 ◽

Vol 6 ◽

pp. 815945 ◽

Cited By ~ 3

Author(s):

Hongjun Zhu ◽

Hongnan Zhao ◽

Qian Pan ◽

Xue Li

Keyword(s):

Erosion Rate ◽

Structural Changes ◽

Fluid Structure Interaction ◽

Fluid Phase ◽

Diameter Ratio ◽

Pipe Diameter ◽

Discrete Phase Model ◽

Two Phase ◽

Fluid Structure ◽

Structure Interaction

A numerical simulation has been conducted to investigate flow erosion and pipe deformation of elbow in gas-solid two-phase flow. The motion of the continuous fluid phase is captured based on calculating three-dimensional Reynolds-averaged-Navier-Stokes (RANS) equations, while the kinematics and trajectory of the discrete particles are evaluated by discrete phase model (DPM), and a fluid-structure interaction (FSI) computational model is adopted to calculate the pipe deformation. The effects of inlet velocity, pipe diameter, and the ratio of curvature and diameter on flow feature, erosion rate, and deformation of elbow are analyzed based on a series of numerical simulations. The numerical results show that flow field, erosion rate, and deformation of elbow are all sensitive to the structural changes and inlet condition changes. Higher inlet rate, smaller curvature diameter ratio, or smaller pipe diameter leads to greater deformation, while slower inlet rate, larger curvature diameter ratio, and larger pipe diameter can weaken flow erosion.

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