Two decades ago, the first edition of this book demystified the process of well log analysis for students, researchers and practitioners. Since then, the industry has changed enormously: technical staffs have been slashed, and hydrocarbons have become increasingly harder to locate, quantify, and produce. In addition, new techniques of drilling have engendered a whole new family of measurement devices incorporated into the drilling string. Petroleum deposits are becoming scarce, while demand steadily increases. Massive corporate restructuring and the "graying" of the workforce have caused the technical competence involved in the search and exploitation of petroleum to become scarce. In this comprehensive update, the authors include all of the new logging measurement technology developed in the last twenty years and expand the petrophysical applications of the measurements. In sum, this is a thoroughly revised graduate level textbook, as well as a useful handbook for any practicing earth scientist.