PROPERTIES OF BLACK OILS - Petroleum Reservoir Fluid Property Correlations - page 88

(3.19g)
Values of solution gas-oil ratios, R s , at reservoir temperatures
and selected reservoir pressures may be obtained using equations
(3.8a)-(3.8f).
The selected correlation equations are not very much more accurate
than the original Standing equations. 37 The values of reservoir oil
densities at pressures less than the bubblepoint pressure calculated
with the recommended procedure are approximately as precise as the
underlying data.
Evaluation of the recommended equation for reservoir oil densities
at reservoir pressures greater than bubblepoint pressure
Equation (3.20) can be used to estimate reservoir oil densities at
pressures above the bubblepoint pressure of the reservoir oil.
(3.20)
This equation is not a correlation; it follows directly from the
definition of the coefficient of isothermal compressibility of oil.
However, correlations are required for c ofb , p b , and ρ oRb . The recommended
correlation equations for these variables, equations (3.13), (3.7), and
(3.18a)-(3.18h), were used in an evaluation of equation (3.20). The use
of equations (3.18a)-(3.18h) to estimate values of ρ oRb ensures that the
results are continuous at the bubblepoint pressure.
Table 3-18 describes the statistics of the data set used to evaluate
this equation. There were 399 reservoir fluid studies, each with a
separator test and several lines of constant composition expansion
data at pressures equal to and above the bubblepoint pressure. The
“laboratory data” for use in evaluating equation (3.20) were determined
by first calculating the reservoir oil density at bubblepoint pressure
for each reservoir fluid study using data from the separator test with a
rearrangement of equation (3.21a). Then the reservoir oil densities for
pressures above bubblepoint pressure for each reservoir fluid study were
calculated by dividing the reservoir oil density at bubblepoint pressure
by the relative oil volumes from the constant composition expansion at
the reported pressures.