Page 45 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Basic Principles, Definitions, and Data 33

where (CN) is the bubble-point pressure correlating number and the other
terms have geen previously defined.
Standing also presents equations for; density correction for compressibility
of liquids; density correction for thermal expansion of liquids; apparent liquid
densities of natural gases; effect of condensate volume on the ratio of surface
gas gravity to well fluid gravity; pseudo-critical constants of gases and con-
densate fluids; pseudo-liquid density of systems containing methane and ethane;
and pseudecritical temperatures and pressures for heptane and heavier.
Beggs and Robinson [7] recently collected PVT data and presented a better esti-
mate of the dead oil viscosity as a function of temperature and oil specific gravity:
POD = lox - 1 (5-25)

where poD = viscosity in cp of the gas-free oil at temperature, T, and X = yT-l.IS3,
y = loz, and Z = 3.0324 - 0.02023 yo, with T in "F and the oil gravity y in "API.
An expression was also given for the saturated oil viscosity, p, or live oil below
the bubblepoint which results from a linear relationship between log poD and
log p for a given value of dissolved gas, Rs:
P = A VBon (5-26)

where A = 10.715 (Rs +
B = 5.44(Rs + 150)-0.338
Rs = sd/STB
In the first book specifically for hand-held calculators, Hollo and Fifadara [32]
presented programs for estimating gas deviation factor (based on data of
Standing and Katz):

Z = 1 + (A, + AJT, + AJT,S)pR + (A4+ AdTR)pR* + A,pR*/T,S (5-27)

where pR= 0.27 P$ZTR T, = T/Tc P, = P/Pc
A, = 0.31506 A, = - 1.0467 A, = - 0.5783
A, = 0.5353 A, = - 0.6123 A, = 0.6815

A program was also presented to calculate the single-phase formation volume
factor using ,the correlation developed by Standing:
:1"" 1.175

io4
Bo = 0.9'72 + 1.47 [ (R,)( + I.,,,] (5-28)

where y, = solution gas specific gravity
yo = stock tank oil specific gravity (141.5/131.5 + "API)
T = temperature, "F
Rs = solution gas-oil ratio, scf/STB
Bo = single-phase formation volume factor, RB/STB
OAPI = stock tank oil gravity, "API
In 1980 Vazquez and Beggs [33] published improved empirical correlations
for some of the commonly required crude oil PVT properties. Their study
utilized a much larger database than was used in previous work so the results