PSEUDO PRESSURE

Real Gas Pseudo-Pressure

The concept of pseudo-pressure or real gas potential is used commonly in gas well deliverability and transient well tests.

The pseudo-pressure is defined by the following integral equation:

Where:

ψ(p) = pseudo-pressure at pressure p, psi2/cp

pb= an arbitrary base pressure (< p), psia

μ = viscosity of gas, cp

z = gas compressibility factor

(Note that μ and z are both functions of pressure. μ increases with pressure. z takes a value of 1 at zero pressure, then initially drops as pressure increases and eventually rises at higher pressures.)

Numerical integration is performed here using the trapeziodal rule with pb = 0.