Reservoir simulation, or modeling, is one of the most powerful techniques currently available to the reservoir engineer. The author, Prof Leonard F Koederitz, (Distinguished Teaching Professor Emeritus at the University of Missouri-Rolla) is a highly notable author and teacher, with many teaching awards. This book has been developed over his twenty years in teaching to undergraduate petroleum engineering students, with the knowledge that they would in all likelihood be model-users, not developers. Most other books on reservoir simulation deal with simulation theory and development. For this book, however, the author has performed model studies and debugged user problems; while many of these problems were actual model errors (especially early on), a fair number of the discrepancies resulted from a lack of understanding of the simulator capabilities, or inappropriate data manipulation. The book reflects changes in both simulation concepts and philosophy over the years, by staying with tried and true simulation practices as well as exploring new methods which could be useful in applied modeling.