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Reservoir EngineeringMaterial Balance and Production

Hydrocarbon Pore Volume Occupied by Evolved Solution Gas Formula

Vg,ev=(NRsiNpRp(NNp)Rs)BgV_{g,ev}=\left(NR_{si}-N_pR_p-(N-N_p)R_s\right)B_g

Hydrocarbon Pore Volume Occupied by Evolved Solution Gas calculates hydrocarbon pore volume occupied by evolved solution gas for material balance and production workflows in reservoir engineering.

Calculate

How engineers use this formula

Use this formula when the listed inputs (N, N_p, R_si, R_s, R_p, B_g) are known and the assumptions behind the cited material balance and production 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, V_g_ev equals 800,000 bbl.

NSTB

1000000

N_pSTB

100000

R_siSCF/STB

600

R_sSCF/STB

400

R_pSCF/STB

800

B_gbbl/SCF

0.005

Inputs

N

STB

Initial Oil in Place

N_p

STB

Cumulative Oil Production

R_si

SCF/STB

Initial Solution Gas-Oil Ratio

R_s

SCF/STB

Current Solution Gas-Oil Ratio

R_p

SCF/STB

Net Cumulative Produced Gas-Oil Ratio

B_g

bbl/SCF

Current Gas Formation Volume Factor

Outputs

V_g_ev

bbl

Hydrocarbon Pore Volume Occupied by Evolved Solution Gas

B_g

bbl/SCF

Current Gas Formation Volume Factor

Source and review

reviewed

Advanced Reservoir Engineering, Ahmed, T., McKinney, P. D. (2005)

Ahmed, T. and McKinney, P. D. 2005. Advanced Reservoir Engineering. Gulf Publishing of Elsevier, Chapter 4, Page 301.

Source

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