Problem 6

The R Sand is a volumetric

reservoir with PVT properties at

150°F shown in the figure to the

right.

When the reservoir pressure is

dropped from an initial pressure

of 2500 psia to an average

pressure of 1600 psia, a total of

26.0 MM STBE of oil was

produced.

The cumulative GOR at 1600 psia

is 954 SCF/STB, and the current

GOR is 2250 SCF/STB. The average

porosity for the field is 18%. No

appreciable amount of water was

produced, and standard

conditions are 14.7 psia and 60°F.

Formation volume factor, bbl/STB

1.30

1.28

1.26

1.24

1.22

1.20

Formation volume factor

Solution GOR

Gas deviation factor

575

0.87

550

0.86 525

0.85 500

0.84

6.6

0.83,

0.82

0.81

1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500

Pressure, psia

400

375

350

Solution GOR, SCF/STB/nProblem 6 (Continued)

Comment

a) Calculate the initial oil in place (OIP).

b) Calculate the SCF of evolved gas remaining in the reservoir at 1600 psia.

c) Calculate the average gas saturation in the reservoir at 1600 psia.

d) Calculate the barrels of oil that would have been recovered at 1600 psia if all

the produced gas had been returned to the reservoir.

e)

Calculate the two-phase volume factor at 1600 psia.

f) Assuming no free gas, calculate the recovery expected by depletion drive

performance down to 2000 psia.

g) Calculate the initial SCF of free gas in the reservoir at 2500 psia.

verify