Reservoir Volume (OOIP) Calculator

Work out reservoir volume (ooip) instantly with clear inputs, formula shown and shareable results.

About Reservoir Volume (OOIP) Calculator

Volumetric OOIP is 7758 x area in acres x net pay in feet x porosity x (1 - water saturation) / formation volume factor, giving stock tank barrels. The constant 7758 converts acre-feet to barrels. Dividing by Boi of about 1.25 converts reservoir barrels to stock tank barrels at surface conditions.

Formula

Volumetric OOIP

OOIP (STB) = 7758 x A (acres) x h (ft) x porosity x (1 - Sw) / Boi

Worked example

With the default values below, Reservoir Volume (OOIP) Calculator returns Original Oil In Place of 88.4784. Change any input above and every figure here is recalculated in your browser.

Inputs used

Reservoir Areaminimum 0 acres: 2,000 acres
Net Pay Thicknessminimum 0 ft: 45 ft
Porosityaccepts 0.01–60 %: 22 %
Water Saturationaccepts 0–100 %: 28 %

Results

Original Oil In Place: 88.4784
Hydrocarbon Pore Volume: 110.5980
Total Pore Volume: 153.6084
Reservoir Bulk Volume: 698.220

Step by step

1Values used
2Volumetric OOIP
3Original Oil In Place= 88.4784
4Hydrocarbon Pore Volume= 110.5980
5Total Pore Volume= 153.6084
6Reservoir Bulk Volume= 698.220

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 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Volumetric estimates for investment or reserve reporting require probabilistic treatment of input uncertainty and certification by a qualified reserves evaluator.

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

Volumetric estimates for investment or reserve reporting require probabilistic treatment of input uncertainty and certification by a qualified reserves evaluator.

Frequently Asked Questions

Which input carries the most uncertainty?

Net pay thickness and area, since both come from seismic interpretation and limited well penetrations. Porosity and saturation from logs are usually better constrained.

Why 7758?

One acre-foot is 43,560 cubic feet, and one barrel is 5.6146 cubic feet, so an acre-foot holds 7758 barrels.