Microemulsion Phase-Behavior Equation-of-State Model Using Empirical Trends in Chemical Potentials

SPE Journal ◽  
2017 ◽  
Vol 23 (03) ◽  
pp. 819-830 ◽  
Author(s):  
V. A. Torrealba ◽  
R. T. Johns
Keyword(s):  
Experimental Data ◽  
Equation Of State ◽  
Phase Behavior ◽  
Correlation Length ◽  
Phase Correlation ◽  
Petroleum Engineering ◽  
Average Curvature ◽  
Three Phase ◽  
Spherical Micelles ◽  
Excess Phases

Summary Surfactant-based enhanced oil recovery (EOR) is a promising technique because of surfactant's ability to mobilize previously trapped oil by significantly reducing capillary forces at the pore scale. However, the field-implementation of these techniques is challenged by the high cost of chemicals, which makes the margin of error for the deployment of such methods increasingly narrow. Some commonly recognized issues are surfactant adsorption, surfactant partitioning to the excess phases, thermal and physical degradation, and scale-representative phase behavior. Recent contributions to the petroleum-engineering literature have used the hydrophilic/lipophilic-difference net-average-curvature (HLD-NAC) model to develop a phase-behavior equation of state (EoS) to fit experimental data and predict phase behavior away from tuned data. The model currently assumes spherical micelles and constant three-phase correlation length, which may yield errors in the bicontinuous region where micelles transition into cylindrical and planar shapes. In this paper, we introduce a new empirical phase-behavior model that is based on chemical-potential (CP) trends and HLD that eliminates NAC so that spherical micelles and the constant three-phase correlation length are no longer assumed. The model is able to describe all two-phase regions, and is shown to represent accurately experimental data at fixed composition and changing HLD (e.g., a salinity scan) as well as variable-composition data at fixed HLD. Further, the model is extended to account for surfactant partitioning into the excess phases. The model is benchmarked against experimental data (considering both pure-alkane and crude-oil cases), showing excellent fits and predictions for a wide variety of experiments, and is compared to the recently developed HLD-NAC EoS model for reference.

A Continuous and Predictive Viscosity Model Coupled to a Microemulsion Equation of State

SPE Journal ◽  
2019 ◽  
Vol 25 (03) ◽  
pp. 1070-1081
Author(s):  
Pooya Khodaparast ◽  
Russell T. Johns
Keyword(s):  
Equation Of State ◽  
Phase Behavior ◽  
Carbon Number ◽  
Viscosity Model ◽  
Model Parameters ◽  
Viscosity Data ◽  
Average Curvature ◽  
Three Phase ◽  
Percolation Thresholds ◽  
Brine Salinity

Summary Surfactant floods can attain high oil recovery if optimal conditions with ultralow interfacial tensions (IFT) are achieved in the reservoir. A recently developed equation-of-state (EoS) phase-behavior net-average-curvature (NAC) model based on the hydrophilic-lipophilic difference (HLD-NAC) has been shown to fit and predict phase-behavior data continuously throughout the Winsor I, II, III, and IV regions. The state-of-the-art for viscosity estimation, however, uses empirical nonpredictive based on of fits to salinity scans, even though other parameters change, such as the phase number and compositions. In this paper, we develop the first-of-its-kind microemulsion viscosity model that gives continuous viscosity estimates in composition space. This model is coupled to our existing HLD-NAC phase-behavior EoS. The results show that experimentally measured viscosities in all Winsor regions (two- and three-phase) are a function of phase composition, temperature, pressure, salinity, and the equivalent alkane carbon number (EACN). More specifically, microemulsion viscosities associated with the three-phase invariant point have an M shape as formulation variables change, such as from a salinity scan. The location and magnitude of viscosity peaks in the M are predicted from two percolation thresholds after tuning to viscosity data. These percolation thresholds as well as other model parameters change linearly with EACN and brine salinity. We also show that the minimum viscosity in the M shape correlates linearly with EACN or the viscosity ratio. Other key parameters in the model are also shown to linearly correlate with the EACN and brine salinity. On the basis of these correlations, two- and three-phase microemulsion viscosities are determined in five-component space (surfactant, two brine components, and two oil components) independent of flash calculations. Phase compositions from the EoS flash calculations are entered into the viscosity model. Fits to experimental data are excellent, as well as viscosity predictions for salinity scans not used in the fitting process.

An Equation-of-State Model To Predict Surfactant/Oil/Brine-Phase Behavior

SPE Journal ◽  
2016 ◽  
Vol 21 (04) ◽  
pp. 1106-1125 ◽  
Author(s):  
S.. Ghosh ◽  
R. T. Johns
Keyword(s):  
Experimental Data ◽  
Equation Of State ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Atmospheric Pressure ◽  
Carbon Number ◽  
Oil Reservoirs ◽  
Potential Candidate ◽  
Average Curvature ◽  
Formulation Variables

Summary Surfactant/polymer (SP) floods have significant potential to recover waterflood residual oil in shallow oil reservoirs. A thorough understanding of surfactant/oil/brine-phase behavior is critical to design SP-flood processes. Current practices involve repetitive laboratory experiments of dead crude at atmospheric pressure in a salinity scan that aims at finding an “optimum formulation” of chemicals for targeted oil reservoirs. Although considerable progress has been made in developing surfactants and polymers that increase the potential of a chemical enhanced-oil-recovery (EOR) project, very little progress has been made to predict phase behavior as a function of formulation variables such as pressure, temperature, and oil equivalent alkane carbon number (EACN). The empirical Hand (1930) plot is still used today to model the microemulsion-phase behavior with little predictive capability because these and other formulation variables change. Such models could lead to incorrect recovery predictions and improper SP-flood designs. In this research, we develop a new predictive-phase-behavior model and introduce a new factor β to account for pressure changes in the HLD equation. This new HLD equation is coupled with the net-average-curvature (NAC) model to predict phase volumes, solubilization ratios, and microemulsion-phase transitions (Winsor II–, Winsor III, and Winsor II+). The predictions of key parameters are compared with experimental data and are within relative errors of 4% (average 2.35%) for measured optimum salinities and 17% (average 10.55%) for optimum solubilization ratios. This paper is the first to use the HLD/NAC model to predict microemulsion-phase behavior for live crudes, including optimal solubilization ratio and the salinity width of the three-phase Winsor III region at different temperatures and pressures. Although the effect of pressure variations on microemulsion-phase behavior is generally thought to be small compared with temperature-induced changes, we show here that this is not necessarily the case. The predictive approach relies on tuning the model to limited experimental data (such as at atmospheric pressure) similar to what is performed for equation-of-state (EOS) modeling of miscible gasfloods. This new EOS-like model could significantly aid the design of chemical floods where key variables change dynamically, and in screening of potential candidate reservoirs for chemical EOR.

scholarly journals Revisiting Kelvin equation and Peng–Robinson equation of state for accurate modeling of hydrocarbon phase behavior in nano capillaries

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ilyas Al-Kindi ◽  
Tayfun Babadagli
Keyword(s):  
Experimental Data ◽  
Surface Tension ◽  
Equation Of State ◽  
Phase Behavior ◽  
Pore Radius ◽  
Microfluidic Chips ◽  
Tight Sandstone ◽  
Kelvin Equation ◽  
Rock Samples ◽  
Robinson Equation

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.

scholarly journals Curvature-Based Equation of State for Microemulsion-Phase Behavior

SPE Journal ◽  
2018 ◽  
Vol 24 (02) ◽  
pp. 647-659 ◽  
Author(s):  
V. A. Torrealba ◽  
R. T. Johns ◽  
H.. Hoteit
Keyword(s):  
Equation Of State ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Industrial Applications ◽  
Data Availability ◽  
Behavior Modeling ◽  
Average Curvature ◽  
Wide Range ◽  
Definition Of ◽  
Spheroidal Geometry

Summary An accurate description of the microemulsion-phase behavior is critical for many industrial applications, including surfactant flooding in enhanced oil recovery (EOR). Recent phase-behavior models have assumed constant-shaped micelles, typically spherical, using net-average curvature (NAC), which is not consistent with scattering and microscopy experiments that suggest changes in shapes of the continuous and discontinuous domains. On the basis of the strong evidence of varying micellar shape, principal micellar curves were used recently to model interfacial tensions (IFTs). Huh's scaling equation (Huh 1979) also was coupled to this IFT model to generate phase-behavior estimates, but without accounting for the micellar shape. In this paper, we present a novel microemulsion-phase-behavior equation of state (EoS) that accounts for changing micellar curvatures under the assumption of a general-prolate spheroidal geometry, instead of through Huh's equation. This new EoS improves phase-behavior-modeling capabilities and eliminates the use of NAC in favor of a more-physical definition of characteristic length. Our new EoS can be used to fit and predict microemulsion-phase behavior irrespective of IFT-data availability. For the cases considered, the new EoS agrees well with experimental data for scans in both salinity and composition. The model also predicts phase-behavior data for a wide range of temperature and pressure, and it is validated against dynamic scattering experiments to show the physical significance of the approach.

scholarly journals Una extensión teórica aplicada a los ácidos puros de cadena larga en la fase líquida para analizar su comportamiento en la fase sólida

2021 ◽  
Vol 34 (2) ◽  
Author(s):  
Moilton Franco Junior ◽  
Nattacia Rocha ◽  
Warley Pereira
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Liquid Phase ◽  
Equation Of State ◽  
Bulk Modulus ◽  
Phase Behavior ◽  
Solid Phase ◽  
The One

In this work, Peng-Robinson EOS (equation of state) was chosen to represent liquid phase behavior. Then, regarding the three acids, Lauric, Palmitic and Stearic, bulk modulus coefficients were calculated in three values of pressures (0.1, 1.0 and 2.0 GPa) and a range of temperature of 350-450 K. According to the literature, results for carbon dioxide, bulk modulus in the liquid phase is in the same line for the one in the solid phase considering the temperature dimension. Based on it, in this work, the bulk modulus was estimated at three temperatures for three acids in solid-phase by extrapolating the results in the liquid phase. Despite there are no experimental data available in the literature, these results seem to be consistent with the thermodynamic constraints, and useful discussions were provided.

Partition-Coefficient Relations for Improved Equation-of-State Description of Microemulsion-Phase Behavior

SPE Journal ◽  
2018 ◽  
Vol 23 (05) ◽  
pp. 1899-1908 ◽  
Author(s):  
V. A. Torrealba ◽  
R. T. Johns
Keyword(s):  
Equation Of State ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Partition Coefficients ◽  
Behavior Modeling ◽  
Surfactant Partition Coefficients ◽  
Partitioning Coefficients ◽  
Excess Phases ◽  
Affinity Quantification ◽  
Behavior Models

Summary Surfactant-mediated enhanced-oil-recovery (EOR) techniques, such as surfactant/polymer (SP) flooding, have received increased attention because of their ability to reduce capillary forces at the pore-scale to ultralow values and mobilize trapped oil. Recently, there have been increased efforts in microemulsion-phase-behavior modeling capabilities by relying on the hydrophilic/lipophilic-difference (HLD) measure for surfactant-affinity quantification. One common assumption of most microemulsion-phase-behavior models is the assumption of pure excess phases, which states that the surfactant component is only present in the microemulsion phase. This assumption can lead to significant errors for some surfactant systems, especially when applied to chemical simulations in which discontinuities may arise. The main novelty of this paper is to allow for surfactant partitioning into both the water and oil excess phases by use of a simple approach, and then relate relevant surfactant-partitioning coefficients (i.e., K-values) to HLD. Surfactant screening that is based on surfactant-structure parameters is also considered based on estimated K-values. Key dimensionless groups are identified as a function of activity coefficients, which allow for a simplified description of the surfactant-partition coefficients. These surfactant-partition coefficients are combined with the chemical-potentials (CP) equation-of-state (EoS) model to describe and predict the phase behavior when the excess phases are not pure. Further, the developed surfactant-partitioning model can be used in other microemulsion-phase-behavior models to allow for impure excess phases.

An Analytical Solution for Three-Component, Two-Phase Surfactant Flooding Dependent on the Hydrophilic/Lipophilic-Difference Equation and the Net-Average-Curvature Equation of State

SPE Journal ◽  
2017 ◽  
Vol 22 (05) ◽  
pp. 1424-1436 ◽  
Author(s):  
Luchao Jin ◽  
Zhitao Li ◽  
Ahmad Jamili ◽  
Mohannad Kadhum ◽  
Jun Lu ◽  
...  
Keyword(s):  
Equation Of State ◽  
Analytical Solution ◽  
Phase Behavior ◽  
Numerical Solutions ◽  
Surfactant Flooding ◽  
Two Phase ◽  
Average Curvature ◽  
Component Displacement ◽  
Behavior Models ◽  
Solution Gas

Summary Microemulsion phase behavior is crucial to surfactant flooding performance and design. In previous studies, analytical/numerical solutions for surfactant flooding were developed dependent on the classical theory of multicomponent/multiphase displacement and empirical microemulsion phase-behavior models. These phase-behavior models were derived from empirical correlations for component-partition coefficients or from the Hand-rule model (Hand 1930), which empirically represents the ternary-phase diagram. These models may lack accuracy or predictive abilities, which may lead to improper formulation design or unreliable recovery predictions. To provide a more-insightful understanding of the mechanisms of surfactant flooding, we introduced a novel microemulsion phase-behavior equation of state (EOS) dependent on the hydrophilic/lipophilic-difference (HLD) equation and the net-average curvature (NAC) model, which is called HLD-NAC EOS hereafter. An analytical model for surfactant flooding was developed dependent on coherence theory and this novel HLD-NAC EOS for two-phase three-component displacement. Composition routes, component profile along the core, and oil recovery can be determined from the analytical solution. The analytical solution was validated against numerical simulation as well as experimental study. This HLD-NAC EOS based analytical solution enables a systematic study of the effects of phase-behavior-dependent variables on surfactant-flooding performance. The effects of solution gas and pressure on microemulsion phase behavior were investigated. It was found that an increase of solution gas and pressure would lead to enlarged microemulsion bank and narrowed oil bank. For a surfactant formulation designed at standard conditions, the analytical solution was able to quantitatively predict its performance under reservoir conditions.

Simulation of Surfactant/Polymer Floods With a Predictive and Robust Microemulsion Flash Calculation

SPE Journal ◽  
2016 ◽  
Vol 22 (02) ◽  
pp. 470-479 ◽  
Author(s):  
Saeid Khorsandi ◽  
Changhe Qiao ◽  
Russell T. Johns
Keyword(s):  
Experimental Data ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Carbon Number ◽  
General Purpose ◽  
Accurate Estimation ◽  
Chemical Flooding ◽  
Two Phase ◽  
Data Set ◽  
Average Curvature

Summary A compositional reservoir simulator that uses a predictive microemulsion phase-behavior model is essential for accurate estimation of oil recovery from surfactant/polymer (SP) floods. Current chemical-flooding simulators, however, use Hand's model (Hand 1939) for phase-behavior calculation. Hand's model can reasonably fit a limited set of experimental data, such as those of a salinity scan, but because it is empirical, it cannot predict phase behavior outside the matched data set. Hydrophyllic/lypophyllic difference (HLD) and net-average-curvature (NAC) equation of state (EOS) (Acosta et al. 2003) has shown great performance for tuning and prediction of experimental data. In this paper, the EOS model with the extension to two-phase regions has been incorporated for the first time into UTCHEM (2000) and our in-house general-purpose compositional simulator, PennSim (2013). All Winsor regions (Type II−, II+, III, and IV) are modeled by use of a consistent physics-based EOS model without the need for Hand's approach. The new simulator is therefore able to account correctly for gridblock properties, which can vary temporally and spatially, and significantly improve the modeling of phase behavior and oil recovery. The results show excellent agreement between UTCHEM and PennSim both in composition space and for composition/saturation profiles for the 1D simulation. The effects of varying pressure, temperature, equivalent alkane carbon number (EACN), and salinity on recoveries are demonstrated also in 1D simulations.

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

Energies ◽  
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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