This book presents the fundamental principles of drilling engineering, with the primary objective of making a good well using data that can be properly evaluated through geology, reservoir engineering, and management. It is written to assist the geologist, drilling engineer, reservoir engineer, and manager in performing their assignments. The topics are introduced at a level that should give a good basic understanding of the subject and encourage further investigation of specialised interests. Many organisations have separate departments, each performing certain functions that can be done by several methods. The re-entering of old areas, as the industry is doing today, particularly emphasises the necessity of good holes, logs, casing design, and cement job. Proper planning and coordination can eliminate many mistakes, and I hope the topics discussed in this book will play a small part in the drilling of better wells. This book was developed using notes, comments, and ideas from a course I teach called "Drilling Engineering with Offshore Considerations".