Refinery Process Fundamentals Curriculum
Module 1 - Crude Oil
Module from the Refinery Process Fundamentals Curriculum curriculum.
CRUDE OIL PROPERTIES & ASSAY INTERPRETATION · Learning Objectives · 1. Classify crude oils by API gravity, sulfur content, and TAN 2. Read and interpret a crude oil assay including TBP, product yields, and property curves 3. Understand the relationship between crude quality and refinery product slate 4. Identify key contaminants and their impact on processing · Crude Oil Classification
| Classification | API Gravity | Sulfur (wt%) | Examples | Processing Characteristics | Typical Products | Relative Value |
|---|---|---|---|---|---|---|
| Light Sweet | 35-50°API | <0.5% | WTI (39.6°), Brent (38.3°), Bonny Light (35.4°) | Easy to process, high naphtha/distillate yield, low residue | Gasoline, jet fuel, diesel, petrochemicals | Premium ($2-5/bbl over benchmark) |
| Light Sour | 35-45°API | >0.5% | Arab Light (33°, 1.8% S), Kirkuk (36°, 2.0% S) | Good yields but requires hydrotreating, H2S in overhead | Same as sweet but higher treating cost | Moderate discount |
| Medium | 25-35°API | Variable | Mars (28.9°), Urals (31.7°), Dubai (31°) | Moderate residue, needs FCC or hydrocracking for conversion | Balanced product slate | Benchmark pricing |
| Heavy Sweet | 15-25°API | <0.5% | Marlim (19.2°), Duri (21.1°) | High residue but low sulfur, good for coker feed | Heavy fuel oil, coker feed, asphalt | Significant discount |
| Heavy Sour | 15-25°API | >1.5% | Arab Heavy (27°, 2.8% S), Maya (21.5°, 3.3% S) | Difficult: high residue, high sulfur, metals (Ni/V) | Requires coking + hydrotreating | Deep discount ($10-20/bbl) |
| Extra Heavy / Bitumen | <15°API | >2% | Boscan (10.1°), Cold Lake (10.2°), Orinoco (8.5°) | Cannot process without diluent or upgrading | Synthetic crude, asphalt | Deepest discount |
| Crude Assay — Key Properties | ||||||
| Property | ASTM Method | Significance | Typical Range | Impact on Refining | Units | |
| API Gravity | D287/D4052 | Density indicator — determines yield structure | 8-50°API | Higher API = more light products, less residue | °API (141.5/SG - 131.5) | |
| Sulfur Content | D4294 (XRF) | Total sulfur — drives treating requirements | 0.01-5.0 wt% | Higher S = more H2 consumption, larger amine/SRU | wt% or ppm | |
| TBP Distillation | D2892/D5236 | True boiling point curve — defines cut points | IBP to 1050°F+ | Determines product yields at given cut points | °F vs vol% | |
| Pour Point | D97 | Lowest temperature crude flows | -60 to +120°F | Affects pumping, storage, pipeline transport | °F | |
| Total Acid Number (TAN) | D664 | Naphthenic acid content — corrosion indicator | 0.01-4.0 mg KOH/g | TAN >0.5 requires metallurgy upgrade (317L SS) | mg KOH/g | |
| Metals (Ni + V) | D5185 (ICP) | Catalyst poisons, especially in FCC and hydro | Ni: 1-100 ppm, V: 1-500 ppm | Concentrate in residue, poison FCC catalyst, foul reactors | ppm (wt) | |
| Salt Content | D3230 | Chloride source — causes corrosion in overhead systems | 1-300 PTB | Must desalt to <1 PTB to protect overhead system | PTB (lb/1000 bbl) | |
| Nitrogen Content | D4629 | Catalyst poison, NOx precursor | 0.01-0.5 wt% | Concentrates in heavy fractions, requires hydrotreating | wt% or ppm | |
| Reid Vapor Pressure | D323 | Vapor pressure at 100°F | 2-15 psi | Affects flashing losses, storage requirements | psi | |
| Wax Content | UOP 46 | Paraffinic wax — affects pour point and processing | 0-20 wt% | Waxy crudes need heated storage, affect lube production | wt% | |
| Source: FOS Chief Files — Module 03 (Nature of Petroleum), Crude Assay handouts (Arabian Light, Forties-Alba) |
Source: Refinery_Process_Fundamentals_Curriculum_v1.xlsx · Sheet: Module 1 - Crude Oil
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