Used to clean the borehole, stabilize rock, control pressures, or enhance drilling rates, drilling fluids and their circulation systems are used in all phases of a drilling operation. These systems are highly dynamic and complicated to model until now. This book provides engineers and students with the necessary analytical/numerical models to handle problems associated with the design and optimization of cost-effective drilling circulation systems. The only book which combines system modeling, design, and equipment, this book provides a clear and rigorous exposition of traditional and non-traditional circulation systems and equipment followed by self contained chapters concerning system modeling applications. Theories are illustrated by case studies based on the author’s real life experience.