This book presents the quintessential guide for gas engineers, emphasizing the practical aspects of natural gas production and it is primarily written for practicing production engineers. I have made every effort to understand the typical needs of an engineer working in the gas field, and have tried to address them. The book is written as a self-help book. After each concept is illustrated, a numerical example is shown to emphasize the concept, and work problems are provided for a better understanding. Realizing that field units are used in the United States, whereas, rest of the world uses SI units, all the numbers as well as equations used in the book are shown using both units.