Foreword to the French Edition

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FOREWORD TO THE FRENCH EDITION The development of hydrocarbon reservoirs follows complex natural laws dependent on a number of factors. The geologist’s goal is to understand the processes of hydrwarbon accumulation. For, simply, the better these are understood, the better are the chances of discovering new hydrocarbon reserves. The fields of geological study are several: sedimentology, structural geology, geochemistry, fluid geology, geophysics. Techniques are becoming continually more sophisticated to keep pace with the demands of modern hydrocarbon exploration. Well-logging plays a particularly important role in geophysics: -well-logs provide an objective, continuous record of a number of properties of the rocks which have been drilled through; -they are the link between geophysical measurements on the surface, and subsurface geology; -they provide numerical data, introducing the possibility of fairly rigorous quantification in the description of sedimentological processes. It is no longer realistic to consider the geological description of a reservoir without incorporating log data, Its omission would effectively exclude most of the information potentially available from drill-holes, which itself represents a significant fraction of the total evidence on which the description can be based. This book was conceived and written by a geologist. I t is hoped it will provide geologists, (and, indeed, all engineers involved in hydrocarbon exploration and reservoir development) with a good understanding of well-logging techniques, and an appreciation of the wealth of information available from log measurements, and their relevance in reservoir description. The present work is the first of a two-volume

series on well-logging. I t deals with the acquisition of log data (tool principles, logging techniques), and describes how the measurements are influenced by the many aspects of the geology of the rocks. The second volume, currently under preparation, will cover in detail log interpretation and applications.

ACKNOWLEDGEMENTS

I wish to express my thanks to my colleagues C. Gras, L. Sulpice and C . Augier of Elf Aquitaine, for their continual encouragement and constructive criticism of the first volume during its initial preparation in French for publication; to G. Herve for his help in preparing the texts and figures for publication; to P. Pain for his humorous illustrations; and to all anonymous draft-men and typists who contributed to this book. I also wish to express my gratitude to Schlumberger for their permission to reproduce figures and texts from their various publications. My thanks are also extended to Dresser-Atlas, SPE of AIME, and SPWLA from whose publications I have borrowed numerous figures. Finally, I thank B. Vivet, Ph. Souhaite, J. Piger, J. Gartner and L. Dupal of Schlumberger Technical Services for their advice and criticism of the original French text; A. Perrodon for his constant support and encouragement; D. Bugnicourt for his advice on numerous points; H. Oertli for his invaluable assistance in editing and correcting the French text; and Elf Aquitaine for their permission to publish this book. OBERTO SERRA. Paris, March 1978