Thousands of pounds are spent in manpower for each reservoir simulation study, just during the data preparation phase. However, few of those involved in this exercise have a clear understanding of the underlying physics and mathematics of reservoir simulation. Consequently, when reservoir simulation results do not agree with field data, engineers face great difficulties in explaining the discrepancy, leaving decision makers and managers in the dark regarding the applicability of reservoir simulation. This book clarifies the background knowledge behind reservoir simulation and makes it easy to have a range of simulation results along with their respective probability. This makes the risk analysis based on knowledge rather than guess work. The book offers by far the strongest tool for engineers and managers to back up reservoir simulation predictions with science, adding transparency and ease to the process of reservoir simulation in a way never witnessed before. Finally, no other book provides readers complete access to the 3D, 3-phase reservoir simulation code. This is a true must-have for all petroleum and reservoir engineers.