Page 12 - Basic Well Log Analysis for Geologist

Preface:

This book is a basic introduction to open hole logging.
Study of the properties of rocks by petrophysical techniques using electric, nuclear, and acoustical sources is as important to a
geologist as the study of rock properties by more conventional means using optical, x-ray, and chemical methods. Nevertheless,
despite the importance of petrophysics. it is frequently underutilized by many geologists who are either intimidated by logging
terminology and mathematics, or who accept the premise that an in-depth knowledge of logging is only marginally useful to their
science because, they feel, it more properly belongs in the province of the log analyst or engincer.
The enormous importance of logging dictates that as geologists, we put aside old notions and apply ourselves diligently to
learning log interpretation. The rewards are obvious; in fact, no less than achieving an understanding of the ancient record hangs in
the balance. And, it is likely that the success or failure of an exploration program may hinge on a geologist’s logging expertise.
In the interest of conciseness. and so that logs used most often in petroleum exploration are thoroughly discussed, the text is
restricted to open hole logs. [ hope that the reader initiates his or her own study of other log types which are beyond the scope of this
book.
Unfortunately. learning about open hole logging requires more of the reader than a light skimming of the text’s material. The plain
truth is that a great deal of hard work, including memorizing log terminology. awaits the serious student; and even then, a facility
with logs develops only after plenty of real-life experience. The intent here is simply to provide a foundation of knowledge which
cin be built upon later. Consequently, many exceptions to rules are left to more advanced books.
It ts quite possible that some colleagues will raise objections about the lack of time devoted to tool theory; they may also comment
on the paucity of qualifying statements in the text. These objections are understood and indeed there may be disagreements about
what constitutes over-simplification. In defense of brevity, it should be pointed out that the surfeit of information available on
petrophysics often discourages all but the most ardent beginner. Certainly, many of the difficult decisions which had to be faced in
preparing the manuscript dealt with selecting information judged indispensable at an elementary level.
Many in the audience will note frequent references to a book by Douglas Hilchie, Golden, Colorado entitled Applied Open Hole
Log Interpretation (1978). For those who are interested in expanding their knowledged of logs, his book will be a great help.
Another helpful book is The Glossary of Terms and Expressions Used in Well Logging. The Society of Professional Well Log
Analysts (1975), which explains the meaning of logging terms by extended definitions.
Finally. a last word - a substantial effort was expended to ensure that a minimum number of errors would appear in the text.
However, given the nature of the subject and the almost infinite possibility for mistakes, there may be slip-ups, regardless; hopefully
they will not be too serious.

George B. Asquith
Pioneer Production Corporation
Amarillo, Texas
October, 1982