The Calculation of Formation Volume Factor and Solution Gas-Oil Ratio from Differential Vaporization and Separator Tests

The data in Tables 7.3 and 7.4 can be combined to yield values for the oil formation volume factor and the solution gas-oil ratio. The formation volume factor is calculated from Eq. (7.6) or (7.7), depending on whether the pressure is above or below the bubble-point pressure: For p > bubble-point pressure,

For p < bubble-point pressure,

where

REV = Relative volume from the flash liberation test listed in Table 7.3 as V/V_b

B_ofb = Formation volume factor from separator tests listed in Table 7.4 as V_b/V_r

B_od = Formation volume factor from differential liberation test listed in Table 7.3 as V/V_r

B_odb = Formation volume factor at the bubble point from differential liberation test

The solution gas-oil ratio can be calculated using Eq. (7.8),

where

R_sofb = Sum of separator gas and the stock-tank gas from separator tests listed in Table 7.4

R_sod = Solution gas-oil ratio from differential liberation test listed in Table 7.3

R_sodb = The value of R_sod at the bubble point

For example, at a pressure of 5000 psia and separator conditions of 200 psig and 77°F,

B_o = 0.9739 (1.337) = 1.302 bbl/STB

and

R_so = 459 + 98 = 557 SCF/STB

(Recall that R_so = R_sob for pressures above the bubble point.)

At a pressure of 2512 psig, which is below the bubble-point pressure, B_o and R_so become

and