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Reservoir fluid properties (PVT)Metric units Unit converter

Gas molecular weight and density

Molecular weight of gas from its composition (in %), and the gas density at normal (0 °C) and standard (20 °C) conditions.

Formula
M = (Y₁ × 16.043 + Y₂ × 30.07 + Y₃ × 44.097 + Y₄ × 58.024 + Y₅ × 72.151 + Y₆ × 44.010 + Y₇ × 34.080 + Y₈ × 28.014) / 100; ρ₀ = M / 22.414; ρ₂₀ = M / 24.05

Error in the original: the code uses 58.024 g/mol for butane (C₄H₁₀) instead of the 58.124 g/mol shown on the page, so the molecular weight is low by 0.001 × Y₄ g/mol (0.005 g/mol at 5 % butane) and the densities proportionally. The calculation is kept as in the original.

Inputs

You can change a field's unit: the value is converted to the formula's units automatically.

Y₁%
Y₂%
Y₃%
Y₄%
Y₅%
Y₆%
Y₇%
Y₈%
Unit converter for this formulaDensity and °API
Metric
  • kg/m³850
  • g/cm³0.85
  • t/m³0.85
  • rel. (water 4 °C)0.850024
US field units
  • lb/ft³53.0638
  • lb/gal (ppg)7.09359
  • SG (60/60 °F)0.850837
  • °API34.8068

°API and SG refer to the density at 60 °F (15.6 °C) relative to water at 60 °F, relative density to water at 4 °C. The oil's thermal expansion between the measurement temperatures is not included. °API = 141.5 / SG − 131.5.

All units →
Result
M — Gas molecular weight
0.00
g/mol
  • ρ₀ — Gas density at normal conditions (0 °C)
    0.000
  • ρ₂₀ — Gas density at standard conditions (20 °C)
    0.000

More in Reservoir fluid properties (PVT)

Degassed oil viscosity at standard conditions (0.845 < ρ < 0.924)

Viscosity of degassed oil at standard conditions from its density, for oil with a density of 0.845 to 0.924 g/cm³, in mPa·s.

Degassed oil viscosity at standard conditions (0.78 < ρ ≤ 0.845)

Viscosity of degassed oil at standard conditions from its density, for oil with a density of 0.78 to 0.845 g/cm³, in mPa·s.

Degassed oil viscosity at any temperature

Viscosity of degassed oil at a given temperature from its laboratory viscosity and the coefficient a, in mPa·s. The coefficient c is chosen from the viscosity: 10 for μ > 1000, 100 for 10 ≤ μ ≤ 1000, 1000 for μ < 10.

Coefficient a for oil viscosity

Coefficient a for converting the viscosity of degassed oil to another temperature. The coefficients b and c are chosen from the viscosity: b = 0.00252 and c = 10 for μ > 1000; b = 0.00144 and c = 100 for 10 ≤ μ ≤ 1000; b = 0.00076 and c = 1000 for μ < 10.

Gas-saturated oil viscosity at reservoir conditions

Viscosity of gas-saturated oil at reservoir conditions from the degassed oil viscosity and the correlation coefficients A and B, in mPa·s.

Correlation coefficients A and B

Coefficients A and B for the viscosity of gas-saturated oil, from the gas-oil ratio at 15 °C and atmospheric pressure.

Results are engineering estimates from standard formulas; for design decisions check them against the codes, project documents and specialists' calculations. The formulas carried over from the original set are unchanged, and their errors are described in the notes.