From Elements of Petroleum Geology, Second Edition


Petroleum exploration is largely concerned with the search for oil and gas, two of the chemically and physically diverse group of compounds termed the hydrocarbons. Physically, hydrocarbons grade from gases, via liquids and plastic substances, to solids. The hydrocarbon gases include dry gas (methane) and the wet gases (ethane, propane, butane, etc.). Condensates are hydrocarbons that are gaseous in the subsurface, but condense to liquid when they are cooled at the surface. Liquid hydrocarbons are termed oil, crude oil, or just crude, to differentiate them from refined petroleum products. The plastic hydrocarbons include asphalt and related substances. Solid hydrocarbons include coal and kerogen. Gas hydrates are ice crystals with peculiarly structured atomic lattices, which contain molecules of methane and other gases. This chapter describes the physical and chemical properties of natural gas, oil, and the gas hydrates; it is a necessary prerequisite to Chapter 5, which deals with petroleum generation and migration. The plastic and solid hydrocarbons are discussed in Chapter 9, which covers the tar sands and oil shales.

The earth s atmosphere is composed of natural gas. In the oil industry, however, natural gas is defined as a mixture of hydrocarbons and varying quantities of nonhydrocarbons that exists either in the gaseous phase or in solution with crude oil in natural underground reservoirs. The foregoing is the definition adopted by the American Petroleum Institute (API), the American Association of Petroleum Geologists (AAPG), and the Society of Petroleum Engineers (SPE). The same authorities subclassify natural gas...

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Gas Compressors and Gas Compressor Systems
Gas compressors and gas compressor systems circulate gas through a process, enhance conditions for chemical reactions, provide inert gas for safety or control systems, recover and recompress process gas, and maintain correct pressure levels by either adding and removing gas or vapors from a process system.
Petroleum and Mineral Oil Products
Petroleum products and mineral oil products include substances such as fluids and greases.
Chemical Process and Petrochemical Gases

Chemical process and petrochemical gases are materials used in the production of compounds or products. They are used in processes such as inerting, blanketing, purging, sparging, and stripping. These gases are used in many applications including treatment and sterilization, medicine, energy solutions, and manufacturing.

Industrial Gases
Industrial gases are pure elements, molecular compounds or mixtures that are gaseous or vaporous at room temperature and pressure.
Fuels and Fuel Products
Fuels and fuel products include gasoline, diesel oil, natural gas, propane, coal, fossil fuels, biofuels and other combustible fluids or materials.

Topics of Interest

3.1 WELL DRILLING AND COMPLETION In the earliest days of oil exploration, oil was collected from surface seepages. Herodotus, writing in about 450 B.C., described oil seeps in Carthage (Tunisia) and...

9.1 INTRODUCTION The petroleum geologist is largely concerned with exploring for crude oil and natural gas, and the major part of this book is devoted to this theme. Vast amounts of energy, however,...

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INTRODUCTION Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are...