The compounds in crude petroleum oil are essentially hydrocarbons or substituted
hydrocarbons in which the major elements are carbon at 85%–90% and hydrogen at
10%–14%, and the rest with non-hydrocarbon elements—sulfur (0.2%–3%), nitrogen
(< 0.1–2%), oxygen (1%–1.5%), and organo-metallic compounds of nickel, vanadium,
arsenic, lead, and other metals in traces (in parts per million or parts per billion concentration).
Inorganic salts of magnesium chloride, sodium chlorides, and other mineral
salts are also accompanied with crude oil from the well either because of water
from formation or water and chemicals injected during drilling and production.
