Page 62 - Formulas and Calculations for Petroleum Engineering

Reservoir engineering formulas and calculations Chapter 1 55

1.125 Time to reach the semi-steady state for a gas well in a circular or square
drainage area

Input(s)
m gi : Initial Gas Viscosity (cP)
Ø: Porosity (fraction)
c ti : Initial Total Compressibility (1/psi)
2
A: Drainage Area (ft )
k: Effective Gas Permeability (mD)

Output(s)
t pss : Time (h)

Formula(s)

15:8 Ø m c A
gi
ti
t ¼
pss
k
Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3,
Page: 194.

1.126 Time to the end of infinite-acting period for a well in a circular reservoir

Input(s)
Ø: Porosity (fraction)
m: Viscosity (cP)
c t : Total Compressibility (1/psi)
2
A: Well Drainage Area (ft )
k: Permeability (mD)

Output(s)
t eia : Time to the End of Infinite-acting Period (h)

Formula(s)

380 Ø m c A
t ¼ t
eia
k
Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 1,
Page: 50.

1.127 Torcaso and Wyllie’s correlation for relative permeability ratio prediction

Input(s)

S o : Oil Saturation (fraction)
S wi : Initial Water Saturation (fraction)
krg: Gas Relative Permeability (dimensionless)