Superposition Time Calculator

Calculate equivalent superposition time for well test analysis when production history involves multiple flow rates. Extends Horner analysis to variable-rate tests.

Inputs

Latest Production Time, t_p (hours)

Shut-in Time, Δt (hours)

Initial Rate q₁ (STB/d)

Second Rate q₂ (STB/d)

Duration of First Rate, t₁ (hours)

Final Rate q_n (STB/d)

Results

Equations

Superposition time: t_s = Σ[(q_j-q_j-1)/q_n] × log(Δt_n+t_p,n - t_j-1)

Reference: Odeh & Jones (1965), SPE 1235.

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