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Arps decline

Production forecasting and decline (Arps)

This page describes Production forecasting and decline (Arps) and the associated engineering assessment topics. Project use requires qualified inputs and engineering review.

Decline curve & EUR calculator

Assessment topics

  • Fit a well's history to an Arps model — exponential, hyperbolic or harmonic.
  • Forecast future rate and estimate ultimate recovery (EUR).
  • Report the decline parameters and the forecast assumptions.

Why it matters

Reservoir, production and asset engineers forecast estimated ultimate recovery (EUR) and remaining reserves one well at a time from rate history. Doing it consistently across a whole field — picking the decline exponent b, fitting the same way every time, and reconciling the forecast to an economic cut-off — is repetitive and easy to do subjectively. A standards-traceable Arps fit gives every well the same defensible treatment with the parameters and assumptions written down.

The method — governing equations

Arps decline-curve analysis fits the rate history to one of three empirical models and integrates to recovery at the economic rate:

Rate–time (general / hyperbolic, 0 < b < 1):
  q(t) = qi / (1 + b · Di · t)1/b
  Exponential (b = 0):  q(t) = qi · e−Dit
  Harmonic (b = 1):  q(t) = qi / (1 + Di · t)
Cumulative to an economic rate qab:
  Exponential:  Np = (qi − qab) / Di
  Hyperbolic:  Np = qib / ((1−b)Di) · (qi1−b − qab1−b)
  Harmonic:  Np = (qi / Di) · ln(qi / qab)

where qi is the initial rate, Di the initial nominal decline rate, b the decline exponent and qab the economic abandonment rate. The parameters qi, Di and b are fitted by regression to the history; EUR is the cumulative produced to date plus Np from the current rate to qab.

These are the standard Arps relationships. No numeric example is shown here.

What a screening check covers — and what it does not

Covers

  • Single-well, single-phase boundary-dominated (depletion) decline fits.
  • Exponential, hyperbolic and harmonic models with fitted qi, Di, b.
  • Forward rate forecast and EUR to a user-supplied economic rate.
  • A parameter report with the fit assumptions stated.

Does not cover

  • Transient / early-time flow before boundary-dominated decline, where Arps over-forecasts.
  • Modified-Arps terminal decline or multi-segment fits unless specified.
  • Rate-transient, material-balance or numerical-simulation methods.
  • Well interference, workovers, choke changes, commingled allocation, or economics and pricing.

The screening assumes the history reflects established decline under roughly constant operating conditions; wells in transient flow or with operational changes need a method-of-record review.

Related standards

Arps decline EUR Exponential / hyperbolic / harmonic Decline curve Production forecast

Part of Wells & Subsurface · see the platform engine

Questions

What is Arps decline-curve analysis?

The standard empirical method for forecasting oil and gas production decline — exponential, hyperbolic or harmonic — and estimating ultimate recovery from the rate history.

What assessment outputs are described?

The fitted decline parameters, a forward rate forecast, and the estimated ultimate recovery with the assumptions stated.

Run Arps decline on your own inputs

Every capability is free to explore — open the published dataset behind the check and read the numbers yourself.

Explore capabilities →