Page 25 - Formulas and Calculations for Petroleum Engineering

18 Formulas and calculations for petroleum engineering

Output(s)

a g : Retained Gas Volume of the Total Gas (fraction)

Formula(s)
0 1
N R p
p
a ¼ 1 @ A
g
N R N N R
si p s
Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 4,
Page: 314.

1.37 Fractional gas recovery below the critical desorption pressure in coal
bed methane reservoirs

Input(s)
V m : Langmuir (constant)
G c : Gas Content at Critical Desorption Pressure (SCF/ton)
b: Langmuir (constant)
P: Pressure of Reservoir (psi)
a: Recovery Exponent (dimensionless)

Output(s)
RF: Recovery Factor (fraction)

Formula(s)
a
V m b P
RF ¼ 1 *
G 1+b P
c
Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3,
Page: 223.

1.38 Free gas in place
Input(s)

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

Output(s)

G f : Original Free Gas-in-Place (SCF)

Formula(s)
G ¼ 7758 A h Ø 1 S Þ E
ð
f wi gi
Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3,
Page: 227.