Free Online Decline Curve Analysis Tool: Arps Fit and EUR Forecast

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Load the demo or paste time and rate pairs. Fits run entirely in your browser.
The chart shows your data on a log rate axis with all three Arps fits extrapolated to the economic limit. The table reports initial rate, nominal decline, the b exponent, fit quality, and the reserves each model implies. The spread between the exponential and harmonic EUR is your honest uncertainty range.

Decline curve analysis with your own production data

Paste time and rate pairs from any producing well and the tool above fits all three Arps decline models, exponential, hyperbolic, and harmonic, by least squares. It draws the fits through your data on a semilog rate plot, extrapolates each to your economic limit rate, and reports initial rate, nominal decline, the b exponent, fit quality, estimated ultimate recovery, and remaining life for every model side by side. The best-fitting model is highlighted, but all three stay visible, because the honest answer to how much is left is a range, not a number.

Semilog rate versus time plot with production data points and three Arps decline fits, exponential, hyperbolic, and harmonic, extrapolated to an economic limit line, showing how the b exponent controls the reserves estimate
Three Arps declines through the same history diverge in the future: the spread between exponential and harmonic EUR is the real uncertainty.

This is the sixth tool in the Geoscience Workbench and the production end of the story the suite tells: seismic finds it, logs prove it, the well drills it, and the decline curve says what it was worth. Your production data stays in the browser.

The three Arps declines in one minute

Every Arps model says rate falls at a pace set by the nominal decline Di, and the b exponent says how that pace itself slows. Exponential decline, b of zero, falls at a constant fraction per year and plots as a straight line on semilog paper: typical of boundary-dominated conventional wells. Harmonic decline, b of one, slows so much that cumulative production grows with the logarithm of time. Hyperbolic sits between, and the fitted b is diagnostic: conventional wells usually land between 0 and 0.5, while values near or above 1 are the signature of long transient flow in tight rock, and also the classic way reserves get overstated when a temporary steep-then-flattening trend is extrapolated forever.

Reading the results table

  • EUR to limit is the cumulative production each model implies between now and the economic limit rate you set. The exponential number is the conservative case, harmonic the optimistic one.
  • Time to limit converts the same extrapolation to years of remaining life, which is what facility and abandonment planning actually need.
  • The rms fit error says which model the history prefers, but a good history match never guarantees the forecast: the models genuinely diverge beyond the data.
  • Change the economic limit and refit: reserves are always a statement about a price and cost assumption, and this makes that visible instantly.

What this tool is for

First-pass reserves on a single well, checking a booked EUR against the raw data behind it, and teaching Arps analysis with fits students can reproduce. It fits a single segment, so wells with restimulations or artificial lift changes should be trimmed to the current decline period before pasting. Multi-segment fitting, probabilistic ranges, and type curves belong to commercial packages; the physics and arithmetic here are exactly the same ones they use.

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