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Reservoir EngineeringPVT and Rock-Fluid Properties

Oil Saturation Below Bubble Point During Depletion Formula

So=(1Swi)(1NpN)BoBoiS_o=(1-S_{wi})\left(1-\frac{N_p}{N}\right)\frac{B_o}{B_{oi}}

Oil Saturation Below Bubble Point During Depletion calculates oil saturation for pvt and rock-fluid properties workflows in reservoir engineering.

Calculate

How engineers use this formula

Use this formula when the listed inputs (S_wi, N_p, N, B_oi, B_o) are known and the assumptions behind the cited pvt and rock-fluid 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, S_o equals 0.552 fraction.

S_wifraction

0.25

N_pSTB

200000

NSTB

1000000

B_oibbl/STB

1.25

B_obbl/STB

1.15

Inputs

S_wi

fraction

Initial Water Saturation

N_p

STB

Cumulative Oil Production

N

STB

Oil in Place

B_oi

bbl/STB

Initial Oil Formation Volume Factor

B_o

bbl/STB

Oil Formation Volume Factor

Outputs

S_o

fraction

Oil Saturation

S_wi

fraction

Initial Water Saturation

N_p

STB

Cumulative Oil Production

N

STB

Oil in Place

B_o

bbl/STB

Oil Formation Volume Factor

B_oi

bbl/STB

Initial Oil Formation Volume Factor

Source and review

reviewed

Ahmed, T. and McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 4, Page 312.

Source

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