Reservoir Decline Curve Calculator

Quick-start workflow

1. Pick a preset that resembles your reservoir to populate typical q_i, D_i, and b values, or stay on the custom option to enter measured decline parameters.
2. Adjust the production unit, forecast horizon, table spacing, and optional economic limit to match your planning exercise.
3. Press Generate forecast to compute rates, cumulative production, and the time required to reach the economic cutoff.
4. Give the run a label and click Save scenario to comparison to build a casebook of type curves, step-outs, and sensitivities.
5. Copy the plain-language summary into emails, field reports, or spreadsheets using the Copy summary button.

Arps decline refresher

The general Arps equation models the production rate as $q\left(t\right)=\frac{q}{i_{}}{(1+bDit)}^{-\frac{1}{b}}$.

Cumulative production through time $t$ follows directly:

• Exponential ($b=0$): $N_p=\frac{q}{i_{}}D{i}_{}$.
• Hyperbolic ($b\ne 0$, $b\ne 1$): $N_p=\frac{q}{i_{}}\frac{1}{-}D{i}_{}(1-b)$.
• Harmonic ($b=1$): $N_p=\frac{q}{i_{}}D{i}_{}ln(1+Dit)$.

Because the calculator performs these integrations automatically, you can focus on picking realistic parameters and interpreting results rather than manipulating algebra.

Preset reference

Outputs you receive

Each run reports the rate at the selected horizon, the percentage decline from initial conditions, cumulative production, and the average daily rate. When an economic limit is supplied the tool also provides the time and calendar date (if a start date is entered) when the well is expected to reach that cutoff, together with the cumulative produced by that point.

The forecast table lists every step with rate, incremental and cumulative production, and optionally a calendar date. Use shorter spacings to inspect the early transient decline, or wider spacings to frame long-term facilities planning.

Worked example

Consider a shale oil well with q_i = 1,000 bbl/day, D_i = 0.75 1/yr, b = 0.85, an economic limit of 65 bbl/day, and a five-year horizon. The calculator reports:

• Year-five rate near 96 bbl/day (a 90% decline from initial production).
• Five-year cumulative of roughly 540 thousand barrels, averaging 295 bbl/day over the window.
• Economic limit reached after 5.5 years, equivalent to late Q2 of year six if production started 1 January 2024.

The scenario log can then retain this base case while you adjust D_i or b to test completion designs or artificial-lift upgrades.

Planning checklist

• Cross-check decline parameters against history-matched wells and adjust for expected pressure support changes.
• Review the time-to-limit output alongside lease operating expense (LOE) assumptions to ensure the economic cutoff is realistic.
• Use the average rate and cumulative production metrics to size gathering systems, compression, or artificial lift.
• Log multiple cases to compare drilling campaigns, refrac candidates, or facility constraint scenarios.
• Refresh forecasts when new production data arrives—updated b values or declines can materially shift economic timing.

Frequently asked questions