Page 27 - Formulas and Calculations for Petroleum Engineering

20 Formulas and calculations for petroleum engineering

1.42 Gas cap shrinkage

Input(s)
G pc : Cumulative Gas Production from Gas Cap (SCF)
B g : Gas Formation Volume Factor (bbl/SCF)
m: Gas Cap Ratio (fraction)
N: Oil in Place (STB)
B oi : Initial Oil Formation Volume Factor (bbl/STB)
B gi : Initial Gas Formation Volume Factor (bbl/SCF)

Output(s)
G s : Gas Cap Shrinkage (bbl)

Formula(s)
! !
B g
G ¼ G B m N B 1
s pc g oi
B gi

Reference: Ahmed, T., McKinney, P.D.2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 5,
Page: 333.

1.43 Gas drive index in gas reservoirs

Input(s)
G: Gas Initially in Place (SCF)
G p : Cumulative Gas Production (SCF)
3
B gi : Initial Gas Formation Volume Factor (ft /SCF)
3
B g : Gas Formation Volume Factor (ft /SCF)

Output(s)
GDI: Gas (dimensionless)

Formula(s)
! !
G B gi
GDI ¼ 1
G p B g

Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3,
Page: 211.

1.44 Gas expansion factor
Input(s)

E gi : Initial Gas Expansion Factor (SCF/bbl)
A: Drainage Area (acres)
h: Thickness (ft)
Ø: Porosity (fraction)
S wi : Initial Water Saturation (fraction)
G p : Gas Produced (SCF)