1. Pseudopressure Function
General Equation
Pseudopressure Function or
qg = surface gas rate
a = units conversion factor (see next slide)
k = permeability
h = total thickness
re = external radius
rw = wellbore radius
s = steady-state total skin
D = rate-dependent skin coefficient
pwf = wellbore flowing pressure
pR = volumetric average reservoir pressure
m = gas viscosity
Z = gas Z factor
Bg = gas formation volume factor

2. Gas Rate Equation in Field Units
qg = surface gas rate, scf/d
k = permeability, md
h = total thickness, ft
re = external radius, ft
rw = wellbore radius, ft
s = steady-state total skin
D = rate-dependent skin coefficient, 1/(scf/d)
TR = reservoir temperature, deg R
pwf = wellbore flowing pressure, psi
pR = volumetric average reservoir pressure, psi
m = gas viscosity, cp
Z = gas Z factor
Bg = gas formation volume factor, res.bbl/scf

3. Pseudopressure integral Gas rate is proportional to area under curve
Pwf Pr
Gas rate is proportional to area under curve