Page 59 - Formulas and Calculations for Petroleum Engineering

52 Formulas and calculations for petroleum engineering

1.117 Roach plot for abnormally pressured gas reservoirs

Input(s)
p i /Z i : Initial P/z Ratio (psi)
c t : Rock Compressibility (1/psi)
G p : Gas Produced (SCF)
G: Gas in Place (SCF)

Output(s)

p : Current P/z Ratio (psi)
Z
Formula(s)

p p i G p
¼ 1
Z Z c G
i t
Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3,
Page: 213.

1.118 Rock expansion term in abnormally pressured gas reservoirs

Input(s)
c f : Formation Compressibility (1/psi)
c w : Water Compressibility (1/psi)
S wi : Initial Water Saturation (fraction)

Output(s)
E R : Rock Expansion Term (1/psi)

Formula(s)

c + c S
f w wi
E ¼
R
1 S
wi
Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3,
Page: 213.

1.119 Shape factor—Earlougher

Input(s)
m: Slope of Transient Semi-log Straight Line (psi/log cycle)
0
m : Slope of Semi-steady State Cartesian Straight Line (psi/h)
P 1hr : Pressure at t ¼ 1 h from Transient Semi-log Straight Line (psi)
P : Pressure at t ¼ 0 from Pseudo-steady State Cartesian Straight Line (psi)
Ð
Output(s)

C A : Shape Factor (dimensionless)