ABSTRACT
Petroleum and the equivalent term crude oil is a mixture of gaseous, liquid, and solid molecules that occurs in rock deposits found in different parts of the world. The initial pressure is sufficient to move oil to the production wells and is called the primary oil recovery. Molecules found in crude oils can exist in various states of matter-gas, liquid, or solid-depending on their chemistry, molecular weight, temperature, solvency, and pressure. With a decrease in the temperature, the clusters of wax crystals can grow until no flow is observed, which is reported as the pour point. Crude oils contain hydrocarbons and heteroatom molecules that in turn contain sulfur (S), nitrogen (N), and oxygen (O), and even some metals such as nickel (Ni), vanadium (V), and iron (Fe). Some crude oils are acidic, as indicated by a high total acid number (TAN), and have a significant carbon residue (CCR) and ash content when exposed to high temperatures.
