The study of the structure of rocks composing the earth’s crust has engaged the attention of geologists since the inception of the science of geology. When the idea first dawned that structure was a controlling factor in the accumulation and localization of oil and gas, the oil geologist therefore had ready a great mass of structural information which he could put to practical use. The insistent demands of a rapidly expanding oil industry for new supplies gave fresh impetus to structure studies and this has resulted in recent years in a much more comprehensive and satisfactory understanding of the structure of sedimentary areas not alone of the North American continent but of other similar areas throughout the world.
Structure affecting oil accumulation is a product of various agencies. It can not be considered solely as a product of diastrophism, although this is perhaps the most important direct or indirect cause. For instance, many lensing sands may be explained by vagaries of sedimentation; differential compaction of sediments may result in favorable traps irrespective of deformative stresses;, and varying porosity may be due to differential cementation or to leaching. In any event the size, shape, and position of the sedimentary basins, in and around which oil and gas fields are commonly found, were determined by earth forces operative over great areas, and many of the structural traps are direct results of such forces. Oil geology has contributed in no small degree to a better understanding of diastrophism, paleogeography, sedimentation, and allied branches
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.