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INPUT   DATA

Title

#	Pressure	Viscosity	Compressibility
	(psia)	(cp)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

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OUTPUT   VARIABLES   &   GRAPHS

#	Pressure	Viscosity	Compressibility	Pseudo-Pressure
	(psia)	(cp)		(psi2/cp)x106
1
2
3
:
:
19
20

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

   p_b= 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 p_b = 0.

BIBLIOGRAPHY

• Dake L.P.; Fundamentals Of Reservoir Engineering; Elsevier Scientific Press,Amsterdam, 1978, chap. 8.
• Mian M.A.; Handbook For the Practicing Engineer; Pennwell Publ Co, Tulsa, Oklahoma, 1992, vol. 1, chap. 2.