Oil Formation Volume Factor (Bo) Calculator

Calculate Bo using Standing, Vasquez-Beggs, and other industry correlations

Input Parameters

Enter reservoir and fluid properties

Relative to air (air = 1.0)

About Formation Volume Factor

Bo (oil FVF) is the ratio of oil volume at reservoir conditions to oil volume at standard conditions. Typical values:

  • Light oils (high GOR): 1.2 - 2.0+ bbl/STB
  • Medium oils: 1.1 - 1.5 bbl/STB
  • Heavy oils (low GOR): 1.02 - 1.1 bbl/STB

Results

Enter values and click Calculate to see results

Formula Reference

Standing Correlation (1947)

One of the most widely used correlations, developed from California crude oils.

Bo = 0.9759 + 0.000120 * [ Rs * (gg/go)^0.5 + 1.25*T ]^1.2 Where: Rs = Solution GOR (scf/STB) gg = Gas specific gravity go = Oil specific gravity (from API) T = Temperature (F)

Vasquez-Beggs Correlation (1980)

Developed using over 6,000 data points, with coefficients for different API ranges.

For API <= 30: C1 = 4.677e-4, C2 = 1.751e-5, C3 = -1.811e-8 For API > 30: C1 = 4.670e-4, C2 = 1.100e-5, C3 = 1.337e-9 Bo = 1 + C1*Rs + C2*(T-60)*(API/gg) + C3*Rs*(T-60)*(API/gg)

Glaso Correlation (1980)

Developed from North Sea crude oils.

Bob* = Rs * (gg/go)^0.526 + 0.968*T A = -6.58511 + 2.91329*log(Bob*) - 0.27683*[log(Bob*)]^2 Bo = 1 + 10^A

Bubble Point Pressure (Standing)

Pb = 18.2 * [ (Rs/gg)^0.83 * 10^(0.00091*T - 0.0125*API) - 1.4 ]

Oil Specific Gravity

go = 141.5 / (API + 131.5)