Delineating the well number and trajectory is an important step of any field development project. Drilling a well is an expensive undertaking and if done right, has the potential to tip the NPV of the project from a marginal venture to a liquid gold mine. This book presents a computer-assisted approach of determining the optimal well trajectory using an adjoint-based optimization technique. The algorithm is based on surrounding the wells with dummy wells. The sum of the gradients of the objective function with respect to the flowrate in each dummy well over the life-time of the reservoir is...