PNG 410
APPLIED RESERVOIR ENGINEERING
Homework 5
Due: Thursday, March 30th, 2017 in class
Question 1
A gas-condensate reservoir has an areal extent of 200 acres, an average thickness of
15 ft., an average porosity of 0.18, and an initial water saturation of 0.23. A PVT cell
is used to simulate the production from the reservoir, and the following data are
collected:
Pressure (psia) Wet Gas
Produced (cc)
z
Wet Gas
Condensate Produced
from Separator (moles)
4000 (dew point) 0 0.75 0
3700 400 0.77 0.0003
3300 450 0.81 0.0002
The initial cell volume was 1850 cc, and the initial gas contained 0.002 moles of
condensate. The initial pressure is 4000 psia, and the reservoir temperature is 200
oF. Calculate the amount of dry gas (SCF) and condensate (STB) recovered at 3300
psia from the reservoir. The molecular weight and specific gravity of the condensate
are 145 and 0.8, respectively.
Question 2
Given the following data for a gas-condensate reservoir and the accompanying PVT
test.
4100psia 3400psia 2700psia
C1 0.63 0.6328 0.6539
C2 0.1347 0.144 0.1424
C3 0.083 0.0825 0.081
C4 0.0433 0.0431 0.0411
C5 0.024 0.0226 0.0223
C6+ 0.085 0.075 0.0593
Mol.wt C6+ 139 132.8 117.75
Sp. Gr. C6+ at 60oF 0.79 0.79 0.79
Z-factor for wet gas 0.87 0.8 0.75
at cell T
Wet Gas Prodn. 0 248 543

(cc at cell P,T)
Wet Gas GPM 5.25 4.5 3.3
Retrograde Liquid 0 4 19.8
(% of cell volume)
Initial cell volume 4100 cc
Cell Temperature 186 oF
Reservoir size 200 acres
Thickness 15 ft
Average porosity 0.18
Connate water 0.23
The PVT test indicates 25% liquid recovery of butane, 50% recovery of pentane.
a) What is the liquid recovery of C6+ indicated by the above data?
b) What is the recovery of gross gas, residue gas and condensate at 3400 psia?
c) If the residual hydrocarbon (gas + condensate) saturation is 20%, what is the
recovery of residue gas, assuming complete water influx occurred when the
pressure was 3400 psia and the reservoir pressure stabilized at 3400 psia.
Question 3
Given the following compositional data for a gas condensate reservoir that is at 4000
psia and 180oF:
Component Mole Fraction Ki
C1 0.90 2
C7 0.10 0.1
a) Write the molar balance for the components in the liquid phase and vapor
phase. Solve the resultant equations for the fraction of the initial moles in the
liquid phase (L).
b) Compute the liquid recovery of C1 and C7. What do these numbers mean?
c) If the porosity of the reservoir is 0.2 and the connate water saturation is 0.1
and the bulk rock volume is 1 acre-ft, compute the standard volume of wet gas
initially in place. (C1-Mol.wt. 16, C7 – Mol. Wt. 100).
d) Compute the residue gas to condensate ratio at the initial reservoir conditions.
Assume partial volume of C1 = 0.1 GPM and C7 = 45 GPM