Calculate oil or gas reserves using volumetric inputs. Review porosity saturation factors and recovery assumptions. Turn raw reservoir data into dependable planning numbers fast.
| Fluid | Area | Gross Pay | NTG | Porosity | Sw | FVF | RF | Estimated Recoverable |
|---|---|---|---|---|---|---|---|---|
| Oil | 640 acres | 50 ft | 80% | 18% | 25% | 1.20 | 35% | 7.8201 MMSTB |
| Gas | 320 acres | 80 ft | 70% | 12% | 22% | 0.0052 | 75% | 10.5380 Bscf |
Net Pay: Net Pay = Gross Pay × Net-to-Gross
Hydrocarbon Saturation: Sh = 1 − Sw
Oil In Place: STOIIP = 7758 × A × h × NTG × φ × (1 − Sw) ÷ Boi
Gas In Place: GIIP = 43560 × A × h × NTG × φ × (1 − Sw) ÷ Bg
Recoverable Reserves: Recoverable = In Place × Recovery Factor
In these formulas, A is area in acres, h is gross pay in feet, φ is porosity fraction, Sw is water saturation fraction, and formation volume factor depends on fluid type.
Volumetric reserve estimation is a core reservoir engineering task. It converts mapped rock volume into hydrocarbons in place. This calculator helps engineers screen projects, compare scenarios, and document assumptions. It supports both oil and gas cases. It also estimates recoverable volumes from a user-defined recovery factor.
The workflow starts with reservoir area and gross pay. It then applies net-to-gross, porosity, and water saturation. These values define the hydrocarbon-filled storage space. Formation volume factor converts reservoir volume to surface volume. Recovery factor then estimates the producible share. This sequence follows common volumetric reserve practice.
Area controls reservoir extent. Gross pay represents total thickness before quality screening. Net-to-gross removes non-productive intervals. Porosity measures rock storage capacity. Water saturation reduces the hydrocarbon-filled fraction. Formation volume factor corrects for fluid behavior between reservoir and surface conditions. Recovery factor reflects drive mechanism, well design, and operating limits.
Oil mode returns stock tank barrels and MMSTB. Gas mode returns standard cubic feet and Bscf. That makes the page useful for concept screening, reserve reviews, field development planning, and rapid sensitivity testing. Teams can compare low, base, and high cases without rebuilding spreadsheets for each new assumption set.
Good volumetric estimates depend on good data. Use mapped closure, petrophysical interpretation, core analysis, and fluid studies whenever possible. Cross-check gross pay and net-to-gross with logs and geological models. Review porosity and water saturation ranges carefully. Small changes in these inputs can materially shift the final reserve estimate.
Volumetric output is an engineering estimate, not a substitute for a full reserves audit. The results are strongest during early field assessment and scenario ranking. Update the numbers when new wells, seismic revisions, pressure data, or production history become available. A transparent workflow improves technical communication and supports stronger capital planning.
It estimates hydrocarbons in place from reservoir geometry and rock properties. The method combines area, thickness, net-to-gross, porosity, saturation, and a formation volume factor to produce reserve volumes.
Use oil mode when your formation volume factor and reporting basis are for liquid hydrocarbons. The calculator returns stock tank barrels and MMSTB for easier oil field planning.
Use gas mode when you are estimating gas initially in place and recoverable gas. Results are shown in standard cubic feet and Bscf for practical gas reserve reporting.
Gross pay includes all thickness. Net-to-gross isolates the productive part of that interval. This prevents non-reservoir rock from inflating the reserve estimate.
It converts reservoir fluid volume to surface volume. Oil and gas expand or shrink between reservoir and surface conditions, so this factor is essential for realistic reserve estimates.
Recovery factor is the proportion of in-place hydrocarbons expected to be produced. It depends on reservoir drive, fluid properties, well spacing, completion quality, and development strategy.
Yes. You can enter hectares or square meters for area and meters for thickness. The calculator converts values internally before applying the volumetric formulas.
No. They are engineering estimates for screening and planning. Final booked reserves usually require broader technical review, economic limits, and formal reserve classification standards.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.