This concise technical handbook written to aid drilling engineers and drilling supervisors in underbalanced drilling (UBD) operations includes detailed calculations. In fact, readers can easily code the mathematical models presented in this book and build their own UBD simulators in spreadsheet programs. Guo and Ghalambor cover much needed information on the applications for drilling water wells, mine boreholes, geotechnical boreholes, and oil and gas recovery wells providing illustrative examples throughout the text. Further, they include a complete set of engineering charts with a thorough description of theory and principles. This book makes a great companion for Air and Gas Drilling Manual (McGraw-Hill) and Underbalanced Drilling Manual (GRI). What Gas Volume Requirements for Underbalanced Drilling: Deviated Holes adds is material on multiphase flow in deviated and horizontal well drilling.