Production calculations problem set and screening checklist
PetroCalcHub · Original synthetic teaching exercise · 2026-10-24

Practice inflow coefficients, local velocity, retention arithmetic and the limits of simple screening equations with explicit pressure and volume bases.

Linear PI J = 2 STB/day/psi; pressures use one compatible datum and fluid-volume basis.

1. Which input is still needed to convert PI into a straight-line rate?

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2. Reproduce the baseline Oil rate (STB/day) without rounding intermediate values.

Working: ________________________________________________


3. Compare the first and last recorded scenarios. Which input changes?

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4. What would be needed to apply this example to a different physical system?

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5. What happens to actual pipe speed if ID doubles at fixed local Q?

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6. Compare nominal liquid retention for 10 m³ effective volume at 2 and 4 m³/min.

Working: ________________________________________________


ANSWER KEY

1. Pressure drawdown on a compatible reservoir and flowing-pressure basis.
2. 2 STB/day/psi × 500 psi = 1,000 STB/day. Oil rate (STB/day) = 1000. PI is a coefficient, while rate depends on the selected drawdown.
3. Drawdown (psi) changes from 100 to 1000. Other controls remain as stated in the premise. Oil rate (STB/day) changes from 200 to 2000.
4. Replace the synthetic controls with compatible documented inputs and check the relation's assumptions. This is an inflow relation. An operating point additionally requires an outflow model. PI is a coefficient, while rate depends on the selected drawdown.
5. It becomes one quarter because cross-sectional area increases fourfold.
6. 5 and 2.5 min respectively. A gas-side separation-capacity check is still independent.

Method: Original synthetic teaching calculation. Equations and fixed controls are stated here; these are not field measurements.
Sources:
Vogel (1968): inflow performance for solution-gas-drive wells: https://blasingame.engr.tamu.edu/z_zCourse_Archive/P613_02A/Gas_IPR/00001476.pdf
SLB: productivity index: https://glossary.slb.com/en/terms/p/productivity_index_pi
Madani Sani et al. (2019): API RP 14E origins and limitations: https://www.icmt.ohio.edu/documents/NACE2019/C2019-13206%20Fazlollah%20Madani%20Sani.pdf