Page 208 - Formulas and Calculations for Petroleum Engineering

Well test analysis formulas and calculations Chapter 3 201

Output(s)

t pss : Pseudo steady state (h)

Formula(s)

r 2
tpss ¼ 1200 Ø m c e
t
k
Reference: Pressure Buildup and Flow Tests in Wells, Matthews & Russell, Page: 13.

3.57 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)
2
A: Drainage Area (ft )
k: Effective Gas Permeability (mD)
c ti : Initial Total Compressibility (1/psi)

Output(s)
t pss : Time (h)

Formula(s)

15:8ø 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.

3.58 True wellbore storage coefficient (pressure build-up test)
Input(s)
2
A wb : Cross Sectional Area of Well Bore (ft )
3
r wb : Density of Fluid in Well Bore (lbm/ft )

Output(s)
C: Wellbore Storage Coefficient (BBL/PSI)

Formula(s)

A wb
C ¼ 25:65
r wb

Reference: Lee, J., Rollins, J. B., & Spivey, J. P. (2003). Pressure Transient Testing (Vol. 9). Richardson, Texas: Society of
Petroleum Engineers, Page: 105.