Predictions of three-phase regions in CO2-oil mixtures

Coutinho, João A. P.; Jørgensen, Marianne; Stenby, Erling Halfdan

doi:10.1016/0920-4105(94)00044-5

Cited by 19 publications

(20 citation statements)

References 20 publications

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“…15,16,27 Nghiem and Li, 15 and Cultinho et al 16 compute a narrower region for the threephase region than we do. Nichita et al 27 do a fine job except toward the bicritical point on the right side of Figure 6 and they fail to detect the single phase liquid at the extreme right in.…”

Section: Resultscontrasting

confidence: 52%

“…Nichita et al 27 do a fine job except toward the bicritical point on the right side of Figure 6 and they fail to detect the single phase liquid at the extreme right in. 11 For the Maljamar separator oil, Cultinho et al 16 show a termination of the three-phase region to the left different from ours. Perschke 28 computes a much narrower three-phase region than we do.…”

Section: Resultsmentioning

confidence: 68%

“…13,14 Examination of the literature shows that the computed three-phase envelopes in pressure-composition space are sometimes much smaller than the measured phase envelopes. [15][16][17] While one may suspect the deficiency of the cubic equation used in computations, there may be computational problems that lead to the difference between measured data and predictions. Surprisingly, the solution to the threephase Rachford-Rice equations that comprise part of the successive substitution is believed to be the problem.…”

Section: Introductionmentioning

confidence: 99%

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Efficient and robust three‐phase split computations

2010

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The combination of successive substitution and the Newton method provides a robust and efficient algorithm to solve the nonlinear isofugacity and mass balance equations for two-phase split computations. The two-phase Rachford-Rice equation may sometimes introduce complexity, but the Newton and bisection methods provide a robust solution algorithm. For three-phase split calculations, the literature shows that the computed three-phase region is smaller than measured data indicate. We suggest that an improved solution algorithm for the three-phase Rachford-Rice equations can address the problem. Our proposal is to use a two-dimensional bisection method to provide good initial guesses for the Newton algorithm used to solve the three-phase RachfordRice equations. In this work, we present examples of various degree of complexity to demonstrate powerful features of the combined bisection-Newton method in threephase split calculations. To the best of our knowledge, the use of the bisection method in two variables has not been used to solve the three-phase Rachford-Rice equations in the past. V V C 2010 American Institute of Chemical Engineers AIChE J, 57: [2555][2556][2557][2558][2559][2560][2561][2562][2563][2564][2565] 2011

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Section: Resultscontrasting

confidence: 52%

Section: Resultsmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

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Efficient and robust three‐phase split computations

2010

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“…Use of an EOS provides a purely theoretical investigation, and it does not necessarily lead to quantitatively correct predictions. Various authors later confirmed that other cubic EOSs are also able to predict three-phase behavior at least qualitatively; e.g., Deiters and Schneider (1976), Chaback and Turek (1986), and Deiters and Pegg (1989) for the Redlich-Kwong EOS, Mushrif (2004), Yang (2006), Mushrif and Phoenix (2008), Gauter (1999), Gauter et al (1999), Larson et al (1989), Khan et al (1992), and Creek and Sheffield (1993) for the Peng-Robinson EOS, Gregorowicz and de Loos (1996) and Coutinho et al (1995) for Soave-Redlich-Kwong EOS. Even one of the simplest cubic equations of state, van der Waals EOS, never yields physically absurd predictions ( van Konynenburg 1968).…”

Section: Methods For Systematic Investigationmentioning

confidence: 89%

Mechanisms for High Displacement Efficiency of Low-Temperature CO2 Floods

Okuno

Johns

Sepehrnoori

2010

SPE Improved Oil Recovery Symposium

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CO 2 floods at temperatures typically below 120°F can involve complex phase behavior, where a third CO 2 -rich liquid (L 2 ) phase coexists with the oleic (L 1 ) and gaseous (V) phases. Results of slim-tube measurements in the literature show that an oil displacement by CO 2 can achieve high displacement efficiency of more than 90% when three hydrocarbon-phases coexist during the displacement. However, the mechanism for the high displacement efficiency is uncertain because the complex interaction of phase behavior with flow during the displacement is not fully understood.In this paper, we present the first detailed study of three-phase behavior predictions and displacement efficiency for lowtemperature CO 2 floods. Four-component EOS models are initially used to investigate systematically the effects of pressure, temperature, and oil properties on development of three-phase regions and displacement efficiency. Multicomponent oil displacements by CO 2 are then considered. We use a compositional reservoir simulator capable of robust three-phase equilibrium calculations.Results show that high displacement efficiency of low-temperature CO 2 floods is a consequence of both condensing and vaporizing behavior. The L 2 phase serves as a buffer between the immiscible V and L 1 phases within the three-phase region. Components in the L 1 phase first transfer efficiently to the L 2 phase near a lower critical endpoint (LCEP). These oil components then transfer to the V phase near an upper critical endpoint (UCEP) at the trailing edge of the three-phase region. The CEPs are defined where two of the three coexisting phases merge in the presence of the other immiscible phase. Unlike two-phase displacements, condensation and vaporization of intermediate components occur simultaneously within the threephase region. The simultaneous condensing/vaporizing behavior involving the CEPs is also confirmed for simulations of several west Texas oil displacements. Quaternary fluid models can predict qualitatively the complex displacements because four is the minimum number of components to develop CEP behavior in composition space at a fixed temperature and pressure. SPE 129846measured CO 2 -MMPs for Permian Basin oils always coincide with the lower boundary of the L 1 -L 2 -V regions on the P-x diagrams.The correlation of Orr and Jensen (1984) and the observations of Creek and Sheffield (1993) indicate that existence of a three-phase region plays an important role for high efficiency of low-temperature oil displacements by CO 2 . Measured CO 2 -MMPs reported in the literature typically fall in a pressure range where three hydrocarbon-phases coexist during a displacement. However, it is unknown whether or not the thermodynamic MMP is achieved within such a pressure range. The thermodynamic MMP is defined as the minimum displacement pressure at which complete miscibility is developed along the composition path from injection gas to the reservoir oil for one-dimensional flow in the absence of dispersion.Gas injection theory for oil displacem...

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“…At temperatures usually lower than 120˚F, liquid-vapor (LV), liquid-liquid (L 1 L 2 ), liquid-liquid-vapor (L 1 L 2 V) phase equilibria can occur (Baker et al 1982;Larson et al 1989;Taber 1984, Orr et al 1981;Orr and Jensen 1984;Coutinho et al 1995), where L 1 stands for the oil-rich liquid phase and L 2 stands for the CO 2 -rich liquid phase. Such behavior also occurs for CO 2 -alkanes binary systems, if the alkane is C 14 H 30 or heavier (Orr and Taber, 1984).…”

Section: Introductionmentioning

confidence: 99%

Application of Gibbs Ensemble Monte Carlo to Phase Equilibria of CO2/Hydrocarbon Mixtures

et al. 2013

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Gibbs Ensemble Monte Carlo (GEMC) is a molecular simulation method to predict phase behavior of fluids, such as crude oil and natural gas. It enables us to visualize microscopic structures of fluid phases. In this study, we apply GEMC to phase behavior of CO 2 /oil systems, where the CO 2 -rich liquid (L2) phase can coexist with the oil-rich liquid (L1) phase and vapor (V) phase.The L2 phase can have comparable density as the L1 phase. When the L2 phase is dense enough to extract light and intermediate hydrocarbons, CO 2 flooding can achieve high displacement efficiency of more than 90%. A clear understanding of the L2 phase will help us design CO 2 -solvent injection processes. However, little is known about its microscopic structures and corresponding dynamic properties (i.e., viscosities and diffusion coefficients), apart from densities and phase compositions.The GEMC method is used to calculate phase equilibria of CO 2 /C 16 H 34 mixtures at different pressures at 305 K, which are close to the critical point of CO 2 . Vapor-liquid phase equilibrium is predicted at pressures lower than 75 bar and liquid-liquid phase equilibrium at higher pressures up to 170 bar, where the density of the L2 phase is around 0.868 g/cm 3 and that of L1 phase around 0.871 g/cm 3 . These results are in good agreement with the previous experimental data. By further adding CH 4 and C 2 H 6 into the mixture, liquid/liquid/vapor equilibrium was observed. The mole fraction, density and structural properties such as pair distribution function (which is directly related to the X-Ray diffraction), molecular clustering, and aggregation status of the three different phases are presented. Currently, we are extending our calculations to other CO 2 /hydrocarbon systems and calculating viscosities of two different liquid phases using Molecular Dynamics simulations with the atomic model used for GEMC. TX 75083-3836, U.S.A., fax +1-972-952-9435

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Predictions of three-phase regions in CO2-oil mixtures

Cited by 19 publications

References 20 publications

Efficient and robust three‐phase split computations

Efficient and robust three‐phase split computations

Mechanisms for High Displacement Efficiency of Low-Temperature CO2 Floods

Application of Gibbs Ensemble Monte Carlo to Phase Equilibria of CO2/Hydrocarbon Mixtures

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