Decline curve analysis
Paste a rate history and get an Arps fit — qi, Di and b — with the time to the economic limit, remaining reserves and an EUR.
Production & lift
Build-up test — permeability & skin
A Horner plot from your shut-in pressures, with the semilog slope turned into permeability, skin, p* and flow efficiency.
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How it is calculated
- Horner time (tp + Δt)/Δt on a log axis against shut-in pressure; the late-time points form the radial-flow straight line.
- k = 162.6·q·B·μ/(m·h) from the slope m of that line.
- s = 1.151·[(P₁hr − Pwf)/m − log₁₀(k/(φμct·rw²)) + 3.2275], with P₁hr read off the fitted line rather than off the data.
- p* is the line extrapolated to a Horner time of 1; ΔPskin = 0.87·m·s.
Standards it speaks
Where this stops being true
Horner analysis assumes an infinite-acting homogeneous reservoir, a single constant rate before shut-in, and that the line you fitted is radial flow rather than storage or a boundary. Real tests break at least one of those routinely. p* is not average reservoir pressure — it needs a Matthews–Brons–Hazebroek correction for the drainage shape, which this tool does not apply. A derivative plot decides where the radial line is; a semilog plot alone can be fitted to almost anything, which is why the fit window is yours to move.
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