Oil Well Production Rate Calculator

Work out oil well production rate instantly with clear inputs, formula shown and shareable results.

About Oil Well Production Rate Calculator

Darcy radial inflow for a vertical oil well gives q = 0.00708 k h deltaP / (mu Bo (ln(re/rw) - 0.75)) in stock tank barrels per day, with permeability in millidarcies, thickness in feet and pressure in psi. Productivity index, rate divided by drawdown, is the practical measure of well capability.

Formulas

Radial inflow equation

q (STB/d) = 0.00708 x k x h x deltaP / (mu x Bo x (ln(re/rw) - 0.75))

Productivity index

PI = q / drawdown

Worked example

With the default values below, Oil Well Production Rate Calculator returns Oil Production Rate of 944.50. Change any input above and every figure here is recalculated in your browser.

Inputs used

Reservoir Permeabilityminimum 0 mD: 120 mD
Net Pay Thicknessminimum 0.01 ft: 30 ft
Pressure Drawdownminimum 0.01 psi: 800 psi
Oil Viscosityminimum 0 cP: 2.5 cP

Results

Oil Production Rate: 944.50
Productivity Index: 1.18062
Annual Production: 344,741
Reservoir Transmissibility: 1,440.000

Step by step

1Values used
2Radial inflow equation
3Productivity index
4Oil Production Rate= 944.50
5Productivity Index= 1.18062
6Annual Production= 344,741
7Reservoir Transmissibility= 1,440.000

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.
Well inflow performance for reserves reporting or completion design must be established from pressure transient testing and reservoir modelling by qualified petroleum engineers.

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

Well inflow performance for reserves reporting or completion design must be established from pressure transient testing and reservoir modelling by qualified petroleum engineers.

Frequently Asked Questions

What assumptions does this make?

Steady-state single-phase radial flow into a vertical well in a homogeneous reservoir, with a 1000 ft drainage radius and 4.25 inch wellbore. Real wells deviate through skin damage, multiphase flow and heterogeneity.

What is skin?

A dimensionless factor added inside the log term representing extra pressure drop near the wellbore from drilling damage or stimulation. Positive skin reduces rate; a successful acid or frac job gives negative skin.