The improper selection, combination and composition of the materials used in the water based drilling fluids to control and maintain the fluid properties may lead to various well bore drilling problems like low penetration rate, excessive torque and drag, poor hole cleaning, differential pipe sticking and formation damage and it is a crucial task for a mud engineer to develop optimum water based drilling fluids. This book features the research work carried out by the author in the area of Drilling Fluid Engineering at Indian School of Mines, Dhanbad, India during his Ph.D. programme in Petroleum Engineering. The parts of this book were published in International Journals like Journal of Petroleum Science and Engineering, Energy Sources, Petroleum Science and Technology, Oil Asia Journal (International Edition) and International Conferences like SPE Conference Conference and PETROTECH Conference. Hence, it will serve as a valuable reference to researchers, technologists, academicians, post graduate students and rig personnel concerned with the design and analysis of water based drilling fluids for smooth and safe drilling operations.