Gas Compressibility Z-Factor Calculator

Calculate natural gas compressibility Z-factor using the Papay correlation. Essential for gas reserves, flow rate, and pressure calculations.

Inputs

Reservoir Pressure (psia)

Reservoir Temperature (°F)

Pseudo-Critical Pressure (psia)

Natural gas ≈ 663 psia

Pseudo-Critical Temperature (°R)

Natural gas ≈ 396 °R

Gas Specific Gravity

Relative to air=1.0

Z-Factor

Pseudo-Red. Pressure

Pseudo-Red. Temp

Gas FVF (Bg)

RB/Mscf

Equations

Papay correlation: Z = 1 - (3.52 × P_pr) / (10^(0.9813×T_pr)) + (0.274 × P_pr²) / (10^(0.8157×T_pr))

P_pr = P / P_pc, T_pr = T(°R) / T_pc

Gas FVF: Bg = 0.02829 × Z × T(°R) / P (RB/Mscf)

Note: Papay is accurate for P_pr < 7 and T_pr > 1.4. Use Hall-Yarborough or Dranchuk for higher pressures.

Need gas reservoir engineering, PVT analysis, or reserves estimation?