Page 282 - Introduction to Petroleum Engineering

ACTIVITIES 269
13.7 The production history for a gas reservoir is the following:

G (Bscf) p (psia) Z p/Z
p
0.015 1946 0.813 2393
0.123 1934 0.813 2378
0.312 1913 0.814 2350
0.652 1873 0.815 2297
1.382 1793 0.819 2190
2.21 1702 0.814 2091
2.973 1617 0.828 1953
3.355 1576 0.83 1898
4.092 1490 0.835 1783
4.447 1454 0.838 1734
4.822 1413 0.841 1679
Plot G as a function of p/Z. The x‐axis variable should be p/Z on an x–y
p
coordinate system. Fit a trend line to the plot and determine OGIP.
13.8 A. Use volumetric analysis to estimate OOIP given the following data:

Bulk reservoir volume 9250 acre‐ft
Oil saturation 0.70
Porosity 0.228
Initial pressure P 0 3935 psia
Oil FVF at P is B oi 1.3473 RB/STB
0
Water FVF is B 1.0 RB/STB
w
B. Use the material balance equation for an undersaturated oil reservoir with
water influx to calculate original oil in place. In this case, assume no wa-
ter influx and use the following production data:

Time (days) Pressure (psia) B (RB/STB) N (MSTB)
o p
0 3935 1.3473 0
91 3898 1.3482 46
183 3897 1.3482 91
274 3895 1.3482 137
365 3892 1.3483 183

C. Use the material balance equation for an undersaturated oil reservoir with
water influx to calculate water influx W assuming original oil in place is
e
the value obtained in Part A. The production data is given in Part B.