Reservoir simulation is a major activity for many oil companies; although there are pitfalls in the technology. Flow simulation combined with modern reservoir characterization has proven to be a very effective means for managing the development of reservoirs when properly applied. Reservoir Simulation: History Matching and Forecasting is intended to be a concise introduction to the areas of history matching and reservoir forecasting for those who interact with the reservoir engineer (e.g., geoscientists, production engineers, managers), as well as those who need to interpret or use the results of flow simulation in their work. Following an introductory section, the book is organized according to the major steps for undertaking a simulation study: (1) building the initial geological reservoir and fluid models, (2) choosing the reservoir simulator, (3) improving and validating the reservoir model through history matching, and (4) forecasting and managing/quantifying uncertainties associated with proposed development plans. A final chapter discusses the authors’ view of future trends in reservoir flow simulation and history matching.