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Dive into the research topics where Zhidong Li is active.

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Featured researches published by Zhidong Li.


Spe Journal | 2014

Phase Behavior and Adsorption of Pure Substances and Mixtures and Characterization in Nanopore Structures by Density Functional Theory

Zhidong Li; Zhehui Jin; Abbas Firoozabadi

Phase behavior in shale remains a mystery because of various complexities and effects. One complexity is from nanopores, in which phase behavior is significantly affected by the interaction between the pore surfaces and fluid molecules. The result is the heterogeneous distribution of molecules that cannot be described by bulk-phase thermodynamic approaches. Statistical thermodynamic methods can describe the phase behavior in nanopores. In this work, we apply an engineering density functional theory (DFT) combined with the Peng-Robinson equation of state (EOS) to investigate the adsorption and phase behavior of pure substances and mixtures in nanopores, and include the characterization of pore structure of porous media. The nanopores are represented by carbon-slit pores each consisting of two parallel planar-infinite structureless graphite surfaces. The porous media are activated carbons and dry coal, each modeled by an array of polydisperse carbon-slit pores. We study the influence of multiple factors on phase transitions of various pure light species and their mixtures in nanopores. We find that capillary condensation and hysteresis are more likely in heavier hydrocarbons, at lower temperatures, and in smaller pores. For pure hydrocarbons in nanopores, the phase change always occurs below the critical temperature and saturation pressure. For mixtures in nanopores, there may be a phase change above the cricondentherm. We characterize the pore structure of porous media to obtain the pore-size distribution (PSD), surface area (SA), and pore volume (PV) on the basis of the measured adsorption isotherms of pure substances. Then, we use the computed PSD to predict the adsorption of mixtures in porous media. There is agreement between the experiments and our predictions. This work is in the direction of phase-behavior modeling and understanding in shale media.


Spe Journal | 2012

General Strategy for Stability Testing and Phase-Split Calculation in Two and Three Phases

Zhidong Li; Abbas Firoozabadi

Efficient and robust phase equilibrium computation has become a prerequisite for successful large-scale compositional reservoir simulation. When knowledge of the number of phases is not available, the ideal strategy for phase-split calculation is the use of stability testing. Stability testing not only establishes whether a given state is stable, but also provides good initial guess for phase-split calculation. In this research, we present a general strategy for twoand three-phase split calculations based on reliable stability testing. Our strategy includes the introduction of systematic initialization of stability testing particularly for liquid/liquid and vapor/liquid/liquid equilibria. Powerful features of the strategy are extensively tested by examples including calculation of complicated phase envelopes of hydrocarbon fluids mixed with CO2 in single-, two-, and three-phase regions.


Journal of Chemical Physics | 2009

Interfacial tension of nonassociating pure substances and binary mixtures by density functional theory combined with Peng–Robinson equation of state

Zhidong Li; Abbas Firoozabadi

We develop a density functional theory and investigate the interfacial tension of several pure substances N(2), CO(2), H(2)S, normal alkanes from C(1) to nC(10), and binary mixtures C(1)/C(3), C(1)/nC(5), C(1)/nC(7), C(1)/nC(10), CO(2)/nC(4), N(2)/nC(5), N(2)/nC(6), N(2)/nC(8), N(2)/nC(10), nC(6)/nC(7), nC(6)/nC(8), and nC(6)/nC(10). The theory is combined with the semiempirical Peng-Robinson equation of state (PR-EOS). The weighted density approximation (WDA) is adopted to extend the bulk excess Helmholtz free energy to the inhomogeneous interface. Besides, a supplementary term, quadratic density expansion (QDE), is introduced to account for the long-range characteristic of intermolecular dispersion attractions, which cannot be accurately described by the WDA. In the bulk limit, the QDE vanishes and the theory is reduced to the PR-EOS. For pure substances, the potential expansion parameter is the only adjustable parameter in the QDE and determined by using a single measured interfacial tension at the lowest temperature examined. Then without any parameter adjustment, we faithfully predict the interfacial tensions of pure substances and mixtures over a wide range of conditions.


annual simulation symposium | 2011

Three-Phase Compositional Modeling of CO2 Injection By Higher-Order Finite Element Methods With CPA equation of state

Joachim Moortgat; Zhidong Li; Abbas Firoozabadi

[1] Most simulators for subsurface flow of water, gas, and oil phases use empirical correlations, such as Henry’s law, for the CO2 composition in the aqueous phase, and equations of state (EOS) that do not represent the polar interactions between CO2 and water. Widely used simulators are also based on lowest-order finite difference methods and suffer from numerical dispersion and grid sensitivity. They may not capture the viscous and gravitational fingering that can negatively affect hydrocarbon (HC) recovery, or aid carbon sequestration in aquifers. We present a three-phase compositional model based on higher-order finite element methods and incorporate rigorous and efficient three-phase-split computations for either three HC phases or water-oil-gas systems. For HC phases, we use the Peng-Robinson EOS. We allow solubility of CO2 in water and adopt a new cubic-plus-association (CPA) EOS, which accounts for cross association between H2O and CO2 molecules, and association between H2O molecules. The CPA-EOS is highly accurate over a broad range of pressures and temperatures. The main novelty of this work is the formulation of a reservoir simulator with new EOS-based unique three-phase-split computations, which satisfy both the equalities of fugacities in all three phases and the global minimum of Gibbs free energy. We provide five examples that demonstrate twice the convergence rate of our method compared with a finite difference approach, and compare with experimental data and other simulators. The examples consider gravitational fingering during CO2 sequestration in aquifers, viscous fingering in water-alternating-gas injection, and full compositional modeling of three HC phases.


SPE Improved Oil Recovery Symposium | 2010

General Strategy for Stability Testing and Phase-split Calculations in Two and Three Phases

Zhidong Li; Abbas Firoozabadi

Efficient and robust phase equilibrium computation has become a prerequisite for successful large-scale compositional reservoir simulation. When knowledge of the number of phases is not available, the ideal strategy for phase-split calculation is the use of stability testing. Stability testing not only establishes whether a given state is stable, but also provides good initial guess for phase-split calculation. In this research, we present a general strategy for twoand three-phase split calculations based on reliable stability testing. Our strategy includes the introduction of systematic initialization of stability testing particularly for liquid/liquid and vapor/liquid/liquid equilibria. Powerful features of the strategy are extensively tested by examples including calculation of complicated phase envelopes of hydrocarbon fluids mixed with CO2 in single-, two-, and three-phase regions.


Aiche Journal | 2009

Cubic‐plus‐association equation of state for water‐containing mixtures: Is “cross association” necessary?

Zhidong Li; Abbas Firoozabadi


Energy & Fuels | 2010

Modeling Asphaltene Precipitation by n-Alkanes from Heavy Oils and Bitumens Using Cubic-Plus-Association Equation of State

Zhidong Li; Abbas Firoozabadi


Energy & Fuels | 2010

Cubic-Plus-Association Equation of State for Asphaltene Precipitation in Live Oils

Zhidong Li; Abbas Firoozabadi


Spe Journal | 2013

CO2 Injection in Vertical and Horizontal Cores: Measurements and Numerical Simulation

Joachim Moortgat; Abbas Firoozabadi; Zhidong Li; Rogério Oliveira Espósito


Water Resources Research | 2012

Three‐phase compositional modeling of CO2 injection by higher‐order finite element methods with CPA equation of state for aqueous phase

Joachim Moortgat; Zhidong Li; Abbas Firoozabadi

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Zhehui Jin

University of California

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