The main thrust of this two volume set of books is to illlustrate the practical application of physical principles used in the primary recovery of oil and gas. Examples and procedures for solution of common reservoir problems are covered. The first few chapters stress fundamentals and provide the basis for a thorough understanding of the data needed in reservoir engineering studies. Recovery mechanisms are introduced and steady-state flow concepts and equations are discussed. Volumetric calculations, material balance, and immiscible displacement processes are then presented. Individual chapters are devoted to the analysis of common drive mechanisms.