Fann lab
Type the rotor speeds and dial deflections your crew measured. Both laws are regressed from every reading — τ = τ₀ + K·γ̇ⁿ for Herschel–Bulkley, τ = K·γ̇ⁿ for Power-law — then load the better fit into the model editor.
| Rotor speed (rpm) | Dial / torque (°) | γ̇ (1/s) | τ measured | HB residual | PL residual | |
|---|---|---|---|---|---|---|
| 1,021.4 | 51.25 | -0.04 | 8.91 | |||
| 510.7 | 32.03 | -0.36 | 0.22 | |||
| 340.5 | 24.77 | -0.33 | -2.14 | |||
| 170.2 | 16.55 | -0.21 | -3.67 | |||
| 10.2 | 6.41 | 0.48 | 0.07 | |||
| 5.1 | 5.13 | -0.19 | 0.37 |
Shear stress against shear rate (log scale). Dots are your readings.
Herschel–Bulkley fits better (ΔR² 0.0639); the τ₀ = 4.40 lbf/100ft² yield stress is real.
| Metric | Herschel–Bulkley | Power-law |
|---|---|---|
| Flow behaviour index n | 0.7443 | 0.4126 |
| Consistency K [lbf·sⁿ/100ft²] | 0.2701 | 2.4286 |
| Yield stress τ₀ [lbf/100ft²] | 4.4021 | 0 |
| R² | 0.9996 | 0.9358 |
| RMSE [lbf/100ft²] | 0.3026 | 4.0324 |
| Max residual [lbf/100ft²] | 0.4822 | 8.9059 |
Recommended: Herschel–Bulkley
PV 17.7 cP · YP 12.6 lbf/100ft²
γ̇ window 5.1–1,021 1/s
Pushes the fit through a real well's tubular tally at every stage depth and shows the per-stage ECD, surface budget and closure drift against the advisor.
Runs the advisor on this curve across every stored well and returns the lowest feasible mud weight with the highest feasible pump rate at that weight.
The well's profile solver then runs on these readings — PV/YP come from the fitted curve and the column closure switches to the fitted law.