1. The following reservoir data are given for a five spot pattern in a waterflooding project.
5-spot pattern area 60 acres
pay thickness 120 ft
porosity 0.18
connate water saturation 0.23
residual oil saturation 0.20
oil viscosity 4.0 cp
water viscosity 1.0 cp
end-point oil relative permeability 0.75
end-point water permeability 0.25
oil formation volume factor 1.25
water formation volume factor 1.0
(a) Calculate the total recoverable oil volume originally present in the pattern (in units of STB).
(b) Assuming the displacement to be piston-like, use an appropriate areal sweep correlation to calculate the
volume of oil (in units of STB) recovered from the pattern up to the instant of water breakthrough.
(c) If the water injection rate is kept constant at 1,500 bbl/day, how many days after start of water injection
does the water breakthrough occurs?
(d) What is the volume of water injection needed to recover 80 percent of the moveable oil volume? How
many days is it going to take to reach to this recovery, after breakthrough time?
(2) The following data are applicable to a 5-spot pattern water flood.
Pattern area = 40 acres = 1,742,400 ft²
Height of the reservoir, h 30 ft
Porosity, $\phi$ 15%
Absolute permeability, k 500 md
$\Delta P$ between injection and production wells 900 psi
Radius of wells, $r_w$ 0.375 ft
End point relative permeability to oil, $k_{ro}$ 85.0%
End point relative permeability to water, $k_{rw}$ 30.0%
Connate water saturation, $S_{wc}$ 20%
Initial oil saturation, $S_{oi}$ 80%
Residual oil saturation, $S_{or}$ 25%
Viscosity of oil, $\mu_o$ 1.5 cp
Viscosity of Water $\mu_w$ 1.0 cp
Formation volume factors for oil, $B_o$ 1.15
Formation volume factors water, $B_w$ 1.00
i. Calculate the volume of water that can be injected through each injection well at the start of water injection.
ii. Calculate the well injectivity under flood-out conditions when only water is flowing in the pattern.
iii. Calculate the skin factor for an injection well if the actual initial injectivity is only half of the injectivity calculated
in part 'a' and the production well has zero skin factor.
