It's Not as Easy as it Looks: Revisiting Peng—Robinson Equation of State Convergence Issues for Dew Point, Bubble Point and Flash Calculations

2013 ◽  
Vol 41 (3) ◽  
pp. 188-202 ◽  
Author(s):  
Vamshi Krishna Kandula ◽  
John C. Telotte ◽  
F. Carl Knopf
Keyword(s):  
Equation Of State ◽  
Dew Point ◽  
Bubble Point ◽  
Robinson Equation

Critical Point and Saturation Pressure Calculations for Multipoint Systems (includes associated paper 8871 )

1980 ◽  
Vol 20 (01) ◽  
pp. 15-24 ◽  
Author(s):  
L.E. Baker ◽  
K.D. Luks
Keyword(s):  
Equation Of State ◽  
Critical Point ◽  
Critical Region ◽  
Equations Of State ◽  
Saturation Pressure ◽  
Direct Calculation ◽  
Iterative Solution ◽  
Dew Point ◽  
K Value ◽  
Bubble Point

Abstract Calculation of fluid properties and phase equilibria isimportant as a general reservoir engineering tool andfor simulation of the carbon dioxide or rich gasmultiple-contact-miscibility (MCM) mechanisms. Of particular interest in such simulations is thenear-critical region, through which the compositionalpath must go in an MCM process.This paper describes two mathematical techniquesthat enhance the utility of an equation of state forphase equilibrium calculations. The first is animproved method of estimating starting parameters(pressure and phase compositions) for the iterativesaturation pressure (bubble-point or dew-point)solution of the equation of state. Techniquespreviously have been presented for carrying out thisiterative solution; however, the previously describedprocedure for obtaining initial parameter values wasnot satisfactory in all cases. The improved methodutilizes the equation of state to estimate theparameter values. Since the same equation then isused to calculate the saturation pressure, the methodis self-consistent and results in improved reliability.The second development is the use of the equationof state to calculate directly the critical point of afluid mixture, based on the rigorous thermodynamic criteria set forth by Gibbs. The paper presents aniterative method for solving the highly nonlinearequations. Methods of obtaining initial estimates ofthe critical temperature and pressure also arepresented.The techniques described are illustrated withreference to a modified version of the Redlich-Kwong equation of state (R-K EOS); however, theyare applicable to other equations of state. They havebeen used successfully for a wide variety of reservoirfluid systems, from a simple binary to complexreservoir oils. Introduction MCM processes such as CO2 or rich gas miscibledisplacements (conducted at pressures below thecontact-miscible pressure) traverse a compositional path that goes through the near-critical region. Thishas been described in several papers. Simulationof an MCM process requires the use of an equation of state to describe the liquid- and vapor-phasesaturations and compositions. Fussell and Yanosikdescribed an MVNR (minimum-variableNewton-Raphson)method for solution of a version of theR-K EOS. They discussed some of the difficulties ofobtaining solutions to the equation of state in the near-critical region and showed that the MVNRmethod gave improved results.Experience with the MVNR method hasdemonstrated a need for an improved estimate ofinitial iteration parameters (pressure, phasecompositions)for an iterative solution of saturation(dew-point and bubble-point) pressures. It waslearned that the semitheoretical K-value correlationused for initial estimates usually gave satisfactoryresults when the fluid system contained significantamounts of heavy components (C7+) but was oftenunsatisfactory for fluid systems containing only lightcomponents. This type of system is exemplified bythe fluids in a dry gas-rich gas mixing zone or bymixtures rich in CH4, CO2, or N2.Experience also has demonstrated a need for direct calculation of the critical point. While the MVNRsolution technique discussed by Fussell and Yanosikexhibits improved convergence in the near-critical region, it often is difficult to obtain convergedsolutions of the equation of state at compositionswithin a few percent of the critical composition. SPEJ P. 15＾

New volume translation functions for biodiesel density prediction with the Peng-Robinson Equation of state in terms of its raw materials

Fuel ◽  
2021 ◽  
Vol 293 ◽  
pp. 120254
Author(s):  
Gutierri Salgueiro ◽  
Marcellus de Moraes ◽  
Fernando Pessoa ◽  
Raquel Cavalcante ◽  
André Young
Keyword(s):  
Equation Of State ◽  
Raw Materials ◽  
Density Prediction ◽  
Volume Translation ◽  
Robinson Equation

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.

Modification of the Peng–Robinson equation of state for helium in low temperature regions

2015 ◽  
Vol 54 (4) ◽  
pp. 542-551 ◽  
Author(s):  
Shayan Kaviani ◽  
Farzaneh Feyzi ◽  
Bahareh Khosravi
Keyword(s):  
Equation Of State ◽  
Low Temperature ◽  
Robinson Equation

Compositional Simulation Using an Advanced Peng-Robinson Equation of State

2011 ◽  
Author(s):  
Yizheng Wei ◽  
Zhangxin John Chen ◽  
Marco Satyro ◽  
Chao Charlie Dong ◽  
Hui Deng
Keyword(s):  
Equation Of State ◽  
Compositional Simulation ◽  
Robinson Equation

Determination of Bubble-Point and Dew-Point Pressure Without a Visual Cell

2014 ◽  
Author(s):  
R.. Hosein ◽  
R.. Mayrhoo ◽  
W. D. McCain
Keyword(s):  
Oil And Gas ◽  
Saturation Pressure ◽  
Volatile Oil ◽  
Phase Region ◽  
Gas Condensate ◽  
Dew Point ◽  
Bubble Point ◽  
Point Pressure ◽  
Dew Point Pressure

Abstract Bubble-point and dew-point pressures of oil and gas condensate reservoir fluids are used for planning the production profile of these reservoirs. Usually the best method for determination of these saturation pressures is by visual observation when a Constant Mass Expansion (CME) test is performed on a sample in a high pressure cell fitted with a glass window. In this test the cell pressure is reduced in steps and the pressure at which the first sign of gas bubbles is observed is recorded as bubble-point pressure for the oil samples and the first sign of liquid droplets is recorded as the dew-point pressure for the gas condensate samples. The experimental determination of saturation pressure especially for volatile oil and gas condensate require many small pressure reduction steps which make the observation method tedious, time consuming and expensive. In this study we have extended the Y-function which is often used to smooth out CME data for black oils below the bubble-point to determine saturation pressure of reservoir fluids. We started from the initial measured pressure and volume and by plotting log of the extended Y function which we call the YEXT function, with the corresponding pressure, two straight lines were obtained; one in the single phase region and the other in the two phase region. The point at which these two lines intersect is the saturation pressure. The differences between the saturation pressures determined by our proposed YEXT function method and the observation method was less than ± 4.0 % for the gas condensate, black oil and volatile oil samples studied. This extension of the Y function to determine dew-point and bubble-point pressures was not found elsewhere in the open literature. With this graphical method the determination of saturation pressures is less tedious and time consuming and expensive windowed cells are not required.

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