PVT Calculator

Comprehensive fluid properties analysis using industry-standard correlations

Oil Input Parameters

API Gravity

Gas Specific Gravity

Temperature (F)

Pressure (psia)

Gas-Oil Ratio (scf/STB) - Optional

If provided, used for saturated oil properties

Separator Conditions (for Vasquez-Beggs)

Separator Pressure (psia)

Separator Temperature (F)

Select Correlation

Calculated Oil Properties

PVT Properties

Bubble Point Pressure
--
psia

Solution GOR (Rs)
--
scf/STB

Oil FVF (Bo)

RB/STB

Oil Density

lb/ft3

Viscosity (Beggs-Robinson)

Dead Oil Viscosity

Live Oil Viscosity

Undersaturated Visc

Oil Compressibility

Above Pb (Undersaturated)

psi-1 x 10^-6

Below Pb (Saturated)

psi-1 x 10^-6

State at Current Pressure

Comparison by Correlation

Property	Standing	Vasquez-Beggs	Petrosky
Pb (psia)	--	--	--
Rs (scf/STB)	--	--	--
Bo (RB/STB)	--	--	--

Correlation Selection Guide

Standing: General-purpose, API 16-63, T 100-258F, Pb < 5000 psi

Vasquez-Beggs: Wide range, uses separator conditions for accuracy

Petrosky-Farshad: Gulf of Mexico oils, API 16-45, T 114-288F

Gas Input Parameters

Gas Specific Gravity (air=1)

Temperature (F)

Pressure (psia)

Non-Hydrocarbon Components (mol%)

N2 %

CO2 %

H2S %

Used for Wichert-Aziz correction to pseudocritical properties

Z-Factor Method

Calculated Gas Properties

Pseudocritical Properties (Sutton Correlation)

Ppc (uncorrected)

psia

Tpc (uncorrected)

Ppc (corrected)
--
psia

Tpc (corrected)
--
R

Reduced Properties

Reduced Pressure (Pr)

dimensionless

Reduced Temperature (Tr)

dimensionless

Gas Properties

Z-Factor
--
dimensionless

Gas FVF (Bg)
--
RCF/SCF

Gas Density

lb/ft3

Gas Viscosity

Compressibility

Gas Compressibility (cg)

psi-1 x 10^-4

cg * P

dimensionless

Water Input Parameters

Salinity (ppm or mg/L TDS)

Fresh water: 0, Seawater: ~35,000, Brine: 50,000-300,000

Temperature (F)

Pressure (psia)

Gas Specific Gravity (for Rsw)

Calculated Water Properties

Formation Volume Factor & Density

Water FVF (Bw)
--
RB/STB

Water Density
--
lb/ft3

Viscosity & Gas Solubility

Water Viscosity

Dissolved Gas (Rsw)

scf/STB

Compressibility

Water Compressibility (cw)

psi-1 x 10^-6

cw @ Reservoir

psi-1 x 10^-6

Reference Values

Fresh water at STC: Bw = 1.0, density = 62.4 lb/ft3, mu = 1.0 cp
Typical reservoir brine: Bw = 1.01-1.06, density = 65-75 lb/ft3
Water compressibility: 2.5-4.0 x 10^-6 psi^-1

Generate PVT Property Tables

API Gravity

Gas SG

Temperature (F)

Bubble Point (psia)

Min Pressure (psia)

Max Pressure (psia)

Pressure Step (psi)

Correlation

PVT Property Table

P (psia)	Bo (RB/STB)	Rs (scf/STB)	muo (cp)	rho_o (lb/ft3)	Z	Bg (RCF/SCF)	mug (cp)
Click "Generate Table" to create property data

Property Charts

Bo (Oil FVF)

Rs (Solution GOR)

Bubble Point

Standing Correlation (1947) Bubble Point, Bo, Rs

Bubble Point Pressure

Pb = 18.2 * [(Rs/yg)^0.83 * 10^a - 1.4]

a = 0.00091*T - 0.0125*API

Range: API 16.5-63.8, T 100-258F, Pb 130-7000 psia

Solution GOR

Rs = yg * [(P/18.2 + 1.4) * 10^(-a)]^1.2048

a = 0.00091*T - 0.0125*API

Oil Formation Volume Factor

Bo = 0.9759 + 0.00012 * [Rs*(yg/yo)^0.5 + 1.25*T]^1.2

Reference: Standing, M.B. (1947). "A Pressure-Volume-Temperature Correlation for Mixtures of California Oils and Gases"

Vasquez-Beggs Correlation (1980) Bo, Rs with API Correction

API Gravity Correction

yg_corrected = yg * [1 + 5.912e-5 * API * Tsep * log10(Psep/114.7)]

Solution GOR

For API <= 30: Rs = C1 * yg * P^C2 * exp[C3 * API / (T+460)]

C1=0.0362, C2=1.0937, C3=25.724

For API > 30: Rs = C1 * yg * P^C2 * exp[C3 * API / (T+460)]

C1=0.0178, C2=1.187, C3=23.931

Oil Formation Volume Factor

Bo = 1 + C1*Rs + C2*(T-60)*(API/yg) + C3*Rs*(T-60)*(API/yg)

For API <= 30: C1=4.677e-4, C2=1.751e-5, C3=-1.811e-8

For API > 30: C1=4.67e-4, C2=1.1e-5, C3=1.337e-9

Range: API 15.3-59.5, T 75-294F, P 15-6055 psia, Rs 0-2199 scf/STB

Reference: Vasquez, M. and Beggs, H.D. (1980). "Correlations for Fluid Physical Property Prediction"

Petrosky-Farshad Correlation (1993) Gulf of Mexico Oils

Bubble Point Pressure

Pb = [112.727 * Rs^0.577421 / (yg^0.8439 * 10^X)]^1.7669

X = 4.561e-5 * T^1.3911 - 7.916e-4 * API^1.5410

Solution GOR

Rs = [(Pb/112.727 * 10^X)^0.5657 * yg^0.8439]^1.7326

Oil Formation Volume Factor

Bo = 1.0113 + 7.2046e-5 * [Rs^0.3738 * (yg^0.2914/yo^0.6265) + 0.24626*T^0.5371]^3.0936

Range: API 16.3-45, T 114-288F, Pb 1574-6523 psia, Rs 217-1406 scf/STB

Reference: Petrosky, G.E. and Farshad, F.F. (1993). "Pressure-Volume-Temperature Correlations for Gulf of Mexico Crude Oils"

Beggs-Robinson Viscosity Correlation (1975) Oil Viscosity

Dead Oil Viscosity

muod = 10^X - 1

X = Y * T^(-1.163)

Y = 10^Z, Z = 3.0324 - 0.02023*API

Saturated (Live) Oil Viscosity

muo = A * muod^B

A = 10.715 * (Rs + 100)^(-0.515)

B = 5.44 * (Rs + 150)^(-0.338)

Undersaturated Oil Viscosity

mu = muo_b * (P/Pb)^m

m = 2.6 * P^1.187 * exp(-11.513 - 8.98e-5*P)

Range: API 16-58, T 70-295F, P 132-5265 psia

Reference: Beggs, H.D. and Robinson, J.R. (1975). "Estimating the Viscosity of Crude Oil Systems"

Sutton Correlation (1985) Pseudocritical Properties

Pseudocritical Temperature

Tpc = 169.2 + 349.5*yg - 74.0*yg^2 (R)

Pseudocritical Pressure

Ppc = 756.8 - 131.07*yg - 3.6*yg^2 (psia)

Range: yg 0.57-1.68

Reference: Sutton, R.P. (1985). "Compressibility Factors for High-Molecular-Weight Reservoir Gases"

Wichert-Aziz Correction (1972) Sour Gas Correction

Pseudocritical Correction Factor

epsilon = 120*(A^0.9 - A^1.6) + 15*(B^0.5 - B^4)

A = yH2S + yCO2 (mole fractions)

B = yH2S

Corrected Pseudocritical Properties

Tpc' = Tpc - epsilon

Ppc' = Ppc * Tpc' / (Tpc + B*(1-B)*epsilon)

Reference: Wichert, E. and Aziz, K. (1972). "Calculate Z's for Sour Gases"

Dranchuk-Abou-Kassem (1975) Z-Factor

Z-Factor Equation

Z = 1 + (A1 + A2/Tr + A3/Tr^3 + A4/Tr^4 + A5/Tr^5)*rhor

+ (A6 + A7/Tr + A8/Tr^2)*rhor^2 - A9*(A7/Tr + A8/Tr^2)*rhor^5

+ A10*(1 + A11*rhor^2)*(rhor^2/Tr^3)*exp(-A11*rhor^2)

rhor = 0.27*Pr/(Z*Tr) [Solved iteratively]

Constants

A1=0.3265, A2=-1.0700, A3=-0.5339, A4=0.01569, A5=-0.05165

A6=0.5475, A7=-0.7361, A8=0.1844, A9=0.1056, A10=0.6134, A11=0.7210

Range: 0.2 <= Pr <= 30, 1.0 <= Tr <= 3.0

Reference: Dranchuk, P.M. and Abou-Kassem, J.H. (1975). "Calculation of Z Factors For Natural Gases Using Equations of State"

Hall-Yarborough (1973) Z-Factor

Z-Factor Equation

Z = A * Pr / Y

A = 0.06125 * t * exp(-1.2*(1-t)^2)

t = 1/Tr

Y (Reduced Density) - Solve Iteratively

F(Y) = -A*Pr + (Y + Y^2 + Y^3 - Y^4)/(1-Y)^3

- (14.76*t - 9.76*t^2 + 4.58*t^3)*Y^2

+ (90.7*t - 242.2*t^2 + 42.4*t^3)*Y^(2.18+2.82*t) = 0

Range: 0.1 <= Pr <= 24, Tr >= 1.0

Reference: Hall, K.R. and Yarborough, L. (1973). "A New Equation of State for Z-Factor Calculations"

Lee-Gonzalez-Eakin (1966) Gas Viscosity

Gas Viscosity

mug = K * exp(X * rhog^Y) / 10000 (cp)

K = (9.4 + 0.02*M) * T^1.5 / (209 + 19*M + T)

X = 3.5 + 986/T + 0.01*M

Y = 2.4 - 0.2*X

M = 28.967 * yg (molecular weight)

rhog = P*M / (Z*R*T) (g/cc, use R=10.73)

Range: T 100-340F, P 100-8000 psia, yg 0.55-1.5

Reference: Lee, A.L., Gonzalez, M.H., and Eakin, B.E. (1966). "The Viscosity of Natural Gases"

McCain Water Properties (1991) Bw, Density

Water Formation Volume Factor

Bw = (1 + dVwT) * (1 + dVwP)

dVwT = -1.0001e-2 + 1.33391e-4*T + 5.50654e-7*T^2

dVwP = -1.95301e-9*P*T - 1.72834e-13*P^2*T - 3.58922e-7*P - 2.25341e-10*P^2

Salinity Correction

Bw_brine = Bw_pure * [1 + S*(5.1e-8*P + (5.47e-6 - 1.95e-10*P)*(T-60) - (3.23e-8 - 8.5e-13*P)*(T-60)^2)]

S = salinity in weight percent (ppm/10000)

Reference: McCain, W.D. (1991). "Reservoir Fluid Property Correlations - State of the Art"

Water Viscosity Correlation Viscosity

Pure Water Viscosity

muw_pure = A * T^B (cp)

A = 109.574 - 8.40564*S + 0.313314*S^2 + 8.72213e-3*S^3

B = -1.12166 + 2.63951e-2*S - 6.79461e-4*S^2 - 5.47119e-5*S^3 + 1.55586e-6*S^4

Pressure Correction

muw = muw_pure * (0.9994 + 4.0295e-5*P + 3.1062e-9*P^2)

Range: T 100-400F, P 14.7-10000 psia, S 0-26 wt%

Water Compressibility Compressibility

Water Compressibility (Osif)

cw = 1 / (7.033*P + 541.5*S - 537*T + 403300) (psi^-1)

S = salinity in g/L NaCl

Range: T 200-270F, P 1000-20000 psia, S 0-200 g/L

Reference: Osif, T.L. (1988). "The Effects of Salt, Gas, Temperature, and Pressure on the Compressibility of Water"

Gas Solubility in Water Rsw

Gas-Water Ratio (Rsw)

Rsw_pure = A + B*P + C*P^2 (scf/STB)

A = 8.15839 - 6.12265e-2*T + 1.91663e-4*T^2 - 2.1654e-7*T^3

B = 1.01021e-2 - 7.44241e-5*T + 3.05553e-7*T^2 - 2.94883e-10*T^3

C = -1.0e-7 * (9.02505 - 0.130237*T + 8.53425e-4*T^2 - 2.34122e-6*T^3 + 2.37049e-9*T^4)

Salinity Correction

Rsw = Rsw_pure * 10^(-0.0840655*S*T^(-0.285854))

S = salinity in weight percent

Reference: McCain, W.D. (1991). "Reservoir Fluid Property Correlations"