Natural Gas Hydrates: A Guide for Engineers

Chapter 1: Introduction


In its most general sense, a hydrate is a compound containing water. For example, there is a class of inorganic compounds called solid hydrates. These are ionic solids in which the ions are surrounded by water molecules and form crystalline solids; however, as used in this book, and commonly in the natural gas industry, hydrates are composed of a small molecule and water.

Hydrates are crystalline solid compounds formed from water and smaller molecules. They are a subset of compounds known as clathrates or inclusion compounds. A clathrate compound is one in which a molecule of one substance is enclosed in a structure built up from molecules of another substance. Even though the clathrates of water, the so-called hydrates, are the focus of this work, they are not the only clathrate compounds. For example, urea forms interesting inclusion compounds as well.

Although hydrates were possibly discovered earlier, credit for their discovery is usually given to the famous English chemist, Sir Humphrey Davy. He reported the discovery of the hydrate of chlorine in the early nineteenth century. His equally famous assistant, Michael Faraday, also studied the hydrate of chlorine.

Throughout the nineteenth century, hydrates remained basically an intellectual curiosity. Early efforts focused on finding which compounds formed hydrates and under what conditions they would form. Many of the important hydrate formers were discovered during this era. Not until the twentieth century, however, was the industrial importance of gas hydrates established.

Natural Gas

Even though all terrestrial gases...