A glossary of common terms and abbreviations used in the industry, with links to more in-depth articles on key words
Udex - a solvent extraction process for separating aromatics from reformate. The process uses diethylene glycol as the solvent
UCO - (Unconverted oil) VGO-equivalent bottoms from a hydrocracker unit
UCO - (Used cooking oil) renewable (waste) feedstock used in HEFA units to make renewable diesel and SAF
ULCC - (Ultra-large crude carrier) the largest class of oil tanker, larger than VLCC. ULCC tankers are in the range of 320-560 dwt
ULR - (Unleaed regular gasoline) any gasoline that does not have TEL added to increase octane
ULSD - (Ultra low-sulfur diesel) the standard grade of on-road diesel in the US
Ultra low-sulfur diesel - (ULSD) the standard grade of on-road diesel in the US
Ultraforming - a type of reformer, the refinery process unit that upgrades low-octane heavy naphtha to make gasoline that meets minimum octane requirements
Umm Lulu (crude) - a light, sweet crude grade from the UAE
Unconventional crude - crude oil produced from thin, tight formations using unconventional production techniques including horizontal drilling and hydraulic fracturing
Unicracking - a type of hydrocracker, the unit that upgrades heavy fractions (such as VGO) through thermal catalytic cracking while injecting hydrogen
Unleaded gasoline - (ULR) any gasoline that does not have TEL added to increase octane
Unsaturated - a hydrocarbon that has not been saturated with hydrogen and thus contains double or triple bonds or aromatics rings
Unsaturated gas - refinery gas coming from cracking units that contains unsaturated molecules such as ethylene, propylene and butylene
UOP - (United oil products) one of the major refining process unit technology licensing firms
UOP characterization factor - a measure of the aromaticity/paraffinicity of a crude oil or of a crude oil fraction
Upgrader - a plant used to partially crack extra-heavy crude oil (bitumen) before sending to market
Upper Zakum (crude) - a medium, sour crude grade produced in the UAE
Upstream - the part of the petroleum value chain focused on finding, developing and producing crude oil
Urals (crude) - the most common export grade of crude oil from Russia and an important benchmark for the medium, sour crude market in Europe
US Gulf Coast - (USGC) one of the major refining supply centers and spot market trading hubs
Usan (crude) - a medium, sweet crude grade produced in the Nigeria
USGC - (US Gulf Coast) one of the major refining supply centers and spot market trading hubs
Used cooking oil - (UCO) renewable (waste) feedstock used in HEFA units to make renewable diesel and SAF
Utilities - the non-hydrocarbon processes in a refinery such as power generation, water treatment, and steam generation
Utilization - the ratio of refinery throughput (crude input) to refinery capacity, typically measured in percent