coking

Petroleum is one of the most important substances consumed by man at present time. It is used as a main source of energy for industry, heating, and transportation and it also provides the raw materials for the petrochemical plants to produce polymers, plastics, and many other products. The word petroleum, derived from the Latin words petra and oleum, means literally rock oil and a special type of oil called oleum . Petroleum is a complex mixture of hydrocarbons that occur in the sedimentary rocks in the form of gases (naturalgas), liquids (crude oil), semisolids (bitumen), or solids (wax or asphaltite). Liquid fuels are normally produced from liquid hydrocarbons, although conversion of nonliquid hydrocarbons such as coal, oil shale, and natural gas to liquid fuels is being investigated. In this book, only petroleum hydrocarbons in the form of gas or liquid, simply called petroleum fluids,are considered. Liquid petroleum is also simply called oil. Hydrocarbon gases in a reservoir are called a natural gas or
simply a gas. An underground reservoir that contains hydrocarbons is called petroleum reservoir and its hydrocarbon contents that can be recovered through a producing well is called reservoir fluid. Reservoir fluids in the reservoirs are usually in contact with water in porous media conditions and because they are lighter than water, they stay above the water level under natural conditions.