Fracture conductivity and equivalent skin
Dimensionless fracture conductivity F_CD, the equivalent skin and effective wellbore radius after fracturing from the Cinco-Ley and Samaniego chart, and the fold increase in productivity in pseudo-steady-state flow.
F_CD = k_f · w / (k · x_f)f = (1.65 − 0.328 · u + 0.116 · u²) / (1 + 0.18 · u + 0.064 · u² + 0.005 · u³), u = ln F_CDs_f = f − ln(x_f / r_w), r_w' = x_f · e^(−f)J / J₀ = (ln(r_e / r_w) − 0.75 + s₀) / (ln(r_e / r_w) − 0.75 + s_f)A vertical fracture through the whole pay at the centre of the drainage area, x_f well below r_e, pseudo-steady-state flow. The chart fit holds for 0.1 ≤ F_CD ≤ 1 000; above that the fracture is practically infinitely conductive (r_w' ≈ x_f/2). For a given proppant mass the productivity peaks near F_CD ≈ 1.6.
Source: Cinco-Ley & Samaniego, JPT (1981); Prats (1961); fit and optimum F_CD: Economides, Oligney & Valkó, Unified Fracture Design (2002)
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
From proppant tests at the closure stress, reduced for gel residue and embedment — often several times below the lab value; 1 000 mD·ft = 305 mD·m.
Effective, propped.
√(A/π) from the area per well; 0.564 · L for a square pattern of side L.
Unit converter for this formulaFlow capacity kh, kf·w · Permeability · Length
- mD·m1
- mD·ft3.28084
- s_f — Equivalent skin after fracturing–
- r_w' — Effective wellbore radius–
- J/J₀ — Fold increase in productivity–
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Results are engineering estimates from standard formulas; for design decisions check them against the codes, project documents and specialists' calculations. The formulas carried over from the original set are unchanged, and their errors are described in the notes.