How do you interpret a crude oil assay for refinery planning?

A crude assay provides detailed composition and property data. Key information: API gravity and sulfur content (overall quality indicators), TBP distillation curve (yield of each cut), sulfur distribution by cut, nitrogen and metals content (catalyst deactivation potential), naphtha properties (naphthenes content for reformer feed), middle distillate quality (cetane, pour point, sulfur), vacuum gas oil properties (CCR, metals for FCC/hydrocracker feed), and residue quality (carbon residue, metals for coker/visbreaker). Using assay data: determine product yields at different cut points, estimate utility consumption, evaluate processing difficulty, and calculate refining margins. Compare assays to select crudes that maximize margin given refinery configuration and product requirements.