The primary aim of the book is to present the basic physics of Well Test engineering, using the simplest and most straightforward of mathematical techniques. It is only through having a complete understanding that the engineer can hope to appreciate and solve complex reservoir engineering problems practically. It involves basics of Flow Equations. The book is organised so that it can be used as a textbook for senior and graduate students or as a reference book for practicing engineers. Chapter 1 gives entire details about the field, Chapter 2 mentions statement of problem, Chapter 3 describes the theory and practice of well testing and pressure analysis techniques, which is probably one of the most important subjects in reservoir engineering. Chapter 4 discusses basic assumptions and flow equations along with Darcy’s Equation. Chapter 5 presents Drill Stem Test along with flow periods in details. Chapter 6 focuses on Modular Dynamic Testing, principles, sampling procedures. Chapter 7 illustrates on PVT Analysis and Testing. Chapter 8 explains about the practical Well Test Analysis & Interpretation on real time data on Ecrin Software.Chapter 9 study of designing of Artificial Lift.