Petroleum engineering is a field of engineering that is concerned with the production of crude oil or natural gas. The areas of formation evaluation, reservoir simulation, reservoir engineering, drilling, etc. are crucial to petroleum engineering. Reservoir engineering is a branch of petroleum engineering. It strives to solve the drainage problems that arise during the production of oil and gas reservoirs in order to achieve a high economic recovery. Numerical reservoir modeling, well testing, drilling, PVT analysis of fluids, etc. are central to reservoir engineering. The specializations in reservoir engineering are surveillance engineering and simulation modeling. This book presents the complex subject of petroleum reservoir engineering in the most comprehensible and easy to understand language. It is a valuable compilation of topics, ranging from the basic to the most complex theories and principles in this field. It is a complete source of knowledge on the present status of this important field.