Rw Calibration -- Pickett Plot
Stage 1 of the Archie/Sw hydrocarbon-detection pipeline: fits formation water resistivity (Rw) per reservoir formation via a Pickett-plot lower-envelope regression, across 10 target reservoir formations. Rw is a required input to Archie's equation for computing water saturation (Sw) -- not yet built, this is calibration only.
What "accuracy" means here: This card calibrates Rw only -- it does not compute water saturation (Sw) or flag pay zones (that is a separate, later stage, not yet built). The chart's fitted line is the Sw=1 (100% water-saturated) line at each porosity; real hydrocarbon-bearing rock at the same porosity should read to the RIGHT of it (higher Rt). formation_summary rows are also written into nsta.rw_calibration, the persisted table a future Sw calculation would read from.
Last run: 2026-08-02 10:25:01 UTC
Pickett Plot
Both axes are log scale. Small dots are individual depth samples (downsampled for display). Diamonds are the porosity-binned lower-envelope points the fit actually used. The line is the fitted Sw=1 (100% water-saturated) line -- real hydrocarbon-bearing rock at the same porosity should read to the right of it (higher resistivity).
How this result was generated
Resistivity, and Porosity Log"] formation["Which Formation
Each Depth Belongs To"] waterleg["Remove Depths Already
Flagged as Oil/Gas"] sand["Keep Only Depths the
Sand Model Calls Sand"] porosity["Work Out Porosity
at Each Remaining Depth"] bin["Group Samples by
How Porous They Are"] envelope["Take the Lowest Readings
in Each Group"] fit["Fit One Water Line
Through Those Low Points"] rw["Fitted Rw"] wells --> formation --> waterleg --> sand --> porosity --> bin --> envelope --> fit --> rw
Hover a step for a plain-language explanation.