Classification

By definition (Chapter 1), petroleum (also called crude oil) is a mixture of gaseous, liquid, and

solid hydrocarbon compounds. Petroleum occurs in sedimentary rock deposits throughout

the world and also contains small quantities of nitrogen-, oxygen-, and sulfur-containing

compounds as well as trace amounts of metallic constituents (Bestougeff, 1967; Colombo,

1967; Hobson and Pohl, 1973; Thornton, 1977; Considine and Considine, 1984). Thus, the

classification of petroleum as a hydrocarbon mixture should follow from this definition. But

some clarification is required.