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Phase Behavior and ThermodynamicsGas Properties

Pseudo-Reduced Conditions Formula

Pr=P(PcAPcB)0.5P_r = \frac{P}{(P_{cA}P_{cB})^{0.5}}

Pseudo-Reduced Conditions calculates pseudo-reduced pressure for gas properties workflows in phase behavior and thermodynamics.

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How engineers use this formula

Use this formula when the listed inputs (P, P_cA, P_cB, T, T_cA, T_cB) are known and the assumptions behind the cited gas properties relationship match the engineering case being checked.

Assumptions

  • Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
  • The declared units match the field-unit constants used in the formula.
  • The cited formula applies to the selected petroleum engineering workflow.

Limitations

  • The calculation does not replace a full engineering model or operating procedure.
  • Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.

Common mistakes

  • Mixing unit systems without converting the inputs.
  • Using default example values as field recommendations.
  • Applying the formula outside the source assumptions.

Default example

Using the default inputs, P_r equals 4.375038 dimensionless.

Ppsi

3000

P_cApsi

666

P_cBpsi

706

TK

600

T_cAK

343

T_cBK

550

Inputs

P

psi

Pressure

P_cA

psi

Critical Pressure of Component A

P_cB

psi

Critical Pressure of Component B

T

K

Temperature

T_cA

K

Critical Temperature of Component A

T_cB

K

Critical Temperature of Component B

Outputs

P_r

dimensionless

Pseudo-Reduced Pressure

T_r

dimensionless

Pseudo-Reduced Temperature

P

psi

Pressure

P_cA

psi

Critical Pressure of Component A

P_cB

psi

Critical Pressure of Component B

T

K

Temperature

T_cA

K

Critical Temperature of Component A

T_cB

K

Critical Temperature of Component B

Source and review

reviewed

Bird, R.B., Stewart, W.E. and Lightfoot, E.N. 2002. Transport Phenomena, 2nd ed., Chapter 17, Page 524.

Source

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