Page 260 - Introduction to Petroleum Engineering

ACTIVITIES 247
12.8 A positive skin represents stimulation.

12.9 The wellbore storage effect is due to the volume of the wellbore.
12.10 Radius of investigation is proportional to permeability.

12.6.3 Exercises

12.1 Calculate Horner time for each of the shut‐in times shown in the following
table. The well is allowed to flow for 8 hr before being shut in.

Shut‐In Time (hr) Horner Time

1
12
24
36
12.2 What is the radius of investigation of a pressure buildup (PBU) test in an oil
well when elapsed time (Δt) is 25 hr? Use the pressure buildup data in the
following table.
kt
.
r inv 0 029
c t
Pressure Buildup Test
Production time (t ) 100.0 hr
F
Initial pressure (p ) 2300 psi
i
Initial time 0.0 hr
Reservoir temperature (T) 180.0 °F
Porosity (ϕ) 0.18
Thickness (h) 24.0 ft
Total compressibility (c ) t 1.0 × 10 psia −1
−5
Viscosity (μ) 0.90 cp
Formation volume factor (B) 1.30 RB/STB
Well flow rate (q) 180.0 STB/D
Fluid type Liquid
Permeability (k) 150 md

12.3 A. The mapped boundary closest to a well is approximately 1500 ft away
from the well. Use the information in Exercise 12.2 to calculate the
minimum time (in hr) needed to investigate this distance using a PBU test.
b. Is 25 hr of shut‐in time enough time to see the boundary effect?
12.4 A. Use the Horner plot in Figure 12.3 to find the slope m.
b. Use the pressure buildup data in the following table and slope m to
calculate flow capacity kh = permeability × thickness.
C. Use kh to calculate k.