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Formation Volume Factor Calculator

Work out formation volume factor instantly with clear inputs, formula shown and shareable results.

About Formation Volume Factor Calculator

Standing's correlation gives Bo = 0.9759 + 0.00012 x [Rs x sqrt(gas SG / oil SG) + 1.25 T]^1.2, the ratio of oil volume at reservoir conditions to volume at stock tank conditions. Bo exceeds 1 because dissolved gas and thermal expansion swell the oil underground.

Formulas

Standing correlation

Bo = 0.9759 + 0.00012 x [Rs x sqrt(gamma_g / gamma_o) + 1.25 T]^1.2

Oil gravity

Oil SG = 141.5 / (131.5 + API)

Worked example

With the default values below, Formation Volume Factor Calculator returns Oil Formation Volume Factor of 1.30612. Change any input above and every figure here is recalculated in your browser.

Inputs used

Solution Gas-Oil Ratiominimum 0 scf/STB
500 scf/STB
Gas Specific Gravityaccepts 0.4–2
0.8
Oil Gravityaccepts 5–60 degrees API
35 degrees API
Reservoir Temperatureminimum 32 degrees F
200 degrees F

Results

Oil Formation Volume Factor
1.30612
Oil Specific Gravity
0.84985
Standing Correlation Group
735.11
Reservoir Oil Density
44.767

Step by step

  1. 1Values used
  2. 2Standing correlation
  3. 3Oil gravity
  4. 4Oil Formation Volume Factor= 1.30612
  5. 5Oil Specific Gravity= 0.84985
  6. 6Standing Correlation Group= 735.11
  7. 7Reservoir Oil Density= 44.767

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does Bo matter?

It converts reservoir volumes to sales volumes. A Bo of 1.3 means every barrel produced at surface occupied 1.3 barrels of pore space, which directly scales reserves and material balance calculations.

When is a correlation not good enough?

Whenever PVT laboratory data exists, use it. Correlations carry 5-15% error and were fitted to particular crude families, so volatile oils and heavy crudes are often poorly represented.

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