The study of oil-field waters involves many problems, some physical and others chemical, some theoretical and others practical. From the physical standpoint, inquiry may be made as to how, where, to what extent, and at what rate, true connate water was squeezed out of the sediments which were deposited in it. In the long interval of geologic time, has water been able to pass through such apparently impervious materials as clay or shale or dense limestone? These are questions related to the subject of compaction of sediments (L. F. Athy, this volume, pp. 81123), but they also have a bearing on problems of water circulation and chemical composition. Is underground water circulation generally free, or is this water much more often stagnant? To what extent do the chemical composition and concentration of deep subsurface waters suggest an answer to the foregoing question? Why is the composition of the deep waters, now in the sedimentary strata, generally so different from that of the sea water of to-day? Is there, after all, any truly connate water in sediments which have long been buried in the geologic prism?1 Are the present local characteristics of deep waters related to topographic or physiographic conditions of the time when the containing sediments were laid down, or are they related to structural features developed much later? Can they be used as indices of structural conditions favorable to oil accumulation? Water and oil, although having very low coefficients of expansion, may nevertheless suffer compression under load
Figures & Tables
The AAPG volumes of Structure of Typical American Oil Fields preceed this book, which was written as a sequel to those, and at first conceived as a third volume of the earlier work. This book is designed to review, modify and, if possible, clarify ideas with regard to the fundamental concepts of oil geology, utilizing, for this purpose, the material presented in the two earlier data-based volumes. To conform to the original standard set for it, this book has been kept relatively free from factual data and has been compiled rather as a summation, based upon the best available evidence, of present knowledge of the science. This volume does not include a discussion of the technique of field or laboratory geology, but does include papers divided into 7 parts: History; Origin and evolution of petroleum; Migration and accumulation of petroleum; Relations of petroleum accumulation to structure; Porosity, permeability, compaction; Oil-field waters; and Subsurface temperature gradients.