PROPERTIES OF BLACK OILS - Petroleum Reservoir Fluid Property Correlations - page 98

In addition, Ahmed presented two equations and Al-Marhoun
one equation that do not require the use of coefficients of isothermal
compressibility. 40

Evaluation of proposed correlation equations for oil formation volume
factors at reservoir pressures greater than bubblepoint pressure
An evaluation of these four techniques is given in table 3-21.

Table 3-21. Evaluation of published oil formation volume factor correlation equations for reservoir
pressures above bubblepoint pressure

Predicted oil formation volume factors
ARE, %

Correlation AARE, %

Equation (3.22), B ob from equation (3.21a), c ofb from equation (3.13)* 1.58 2.23

Al-Marhoun (1992)* 1.49 2.31

Ahmed equations 4-65, 4-69 (1989)* 1.49 2.70

Ahmed equations 4-65, 4-70 (1989)* 0.75 2.90

* All correlations evaluated with p b calculated with equation (3.7).

The statistics of the data set used in the evaluation of these
correlations are listed in table 3-18. Each of the 399 reservoir fluid
studies had a separator test and several lines of constant composition
expansion data at pressures above bubblepoint pressure. Values of oil
formation volume factors at pressures above bubblepoint pressure for
use in evaluating published correlations were calculated with these data
using the procedure of Craft and Hawkins. 41
None of these data were used in the preparation of any of these
correlation equations.
The data of table 3-18 were sorted into subsets of approximately
equal size according to reservoir temperatures, stock-tank oil gravities,
reservoir pressures, and measured values of oil formation volume
factors. The results of ARE and AARE calculations for these subsets are
given in figures 3-29 through 3-32.
Also, Labedi offered a set of equations from which oil formation
volumes factors at pressures above bubblepoint pressure can be
estimated. 42 Unfortunately, some of the data required as input to his
equations were not included in the data set used in this evaluation. Thus,
an evaluation of his work for pressures above bubblepoint pressure was
not possible.