Empirical Lithology Crossplot (PEF/RHOB/DT) -- Test Wellbores
Empirical lithology classification check: despiked PEF/RHOB/DT medians per lithology-labeled interval, gated to GR-clean samples only (Clavier Vshale <= 0.15), for 6 hand-picked test wellbores, against published petrophysical matrix endpoints. Scoped to a small test set while the method is developed.
What "accuracy" means here: The "lithology_class" compared against here is NOT verified geological ground truth. It is nsta.lithology_interval, a Lloyd's Register "Sandcount" product built under a 3-year OGA contract from TGS LogLinePlus-joined logs -- professionally produced, but its actual classification algorithm is not documented anywhere in the indexed NSTA package archive. This card checks MUTUAL CONSISTENCY between two independently-derived products (published petrophysical values vs. Sandcount's own picks), not agreement with confirmed truth.
Last run: 2026-07-24 03:03:11 UTC
PEF / RHOB Crossplot
Stars mark the reference mineral point for each class: the published, textbook value for 100% pure, zero-porosity rock (e.g. pure quartz for Sandstone) -- not measured from any of our own wells. Points are clean (Vsh <= 0.15), despiked samples -- real intervals sit off that point due to porosity/impurity, not on it.
DT / RHOB Crossplot
Same clean-sample gate as the PEF/RHOB plot. DT covers a much larger well population than PEF field-wide, so this crossplot is the practical route to extending the method beyond the current PEF-limited test set.
How this result was generated
(identity-verified)"] despike["Within-Run Despike
(MAD, hard bounds)"] vsh["GR -> Clavier Vshale
(per-well P5/P95 baseline)"] gate["Clean-Sample Gate
(Vsh <= 0.15)"] label["nsta.lithology_interval
(SANDCOUNT-derived label)"] median["Median PEF/RHOB/DT
per well x class"] ref["Published Matrix Endpoints"] compare["Deviation Check"] curves --> despike --> vsh --> gate --> median label --> median median --> compare ref --> compare
Hover a step for a plain-language explanation.