Book excerpt: This book is intended primarily as a textbook for geolo gists engaged in petroleum exploration. Its purpose is to introduce the reader to organic geochemistry and to show how to apply geochemistry advantageously in an explora tion program. I have made the explicit assumption that most readers will have a sound background in geology but far less knowledge of, or interest in, chemistry. Be cause there is no need for an exploration geologist to be an expert in organic chemistry, the amount of chemistry used in the book is rather modest. It is, however, often important for a geologist to understand some basic vocab ulary. The emphasis in this book is on applications of geo _chemistry to hydrocarbon exploration. Most of the analyt ical techniques are discussed only briefly, because although a geologist should know what a gas chro matograph is, he or she is unlikely to be asked to repair one. If more detailed knowledge does prove necessary, a laboratory is the proper place to learn. The strengths and weaknesses of the various analytical techniques are discussed so that a geologist will be able to anticipate pitfalls, cull bad data, and choose an appropri ate analytical program. On-the-job experience will prove invaluable in converting the basic information from this text into a practical working knowledge.