A statistical study of 7,241 reservoir sandstones in various oil-producting regions of the United States was completed by a committee of petroleum geologists. The study shows that 68 per cent of the sandstones are of Tertiary age, although each geologic age from Cambrian to Pleistocene, inclusive, is represented. Most of the sandstones are restricted in physical dimensions; they commonly cover less than 100 square miles of areal extent, and have an average thickness of about 39 feet.
The factors which control petroleum accumulation in the sandstones more commonly result from the structural configuration (56 per cent of reservoirs) than from stratigraphie conditions (10 per cent) or from combinations of structural and stratigraphie features (34 per cent), and it is found that the thicker sandstones tend to be broader and better reservoirs than their relative thickness, alone, would suggest. A closer analysis of the sandstones involved in stratigraphie type accumulations shows that 61 per cent of them were deposited under shoreline or nearshore conditions. It is found that 54 per cent of all the reservoir sandstones studied contain mainly oil, 27 per cent contain gas, and the remainder carry substantial amounts of both oil and gas.
Figures & Tables
Geometry of Sandstone Bodies
This volume contains the eight papers presented as a symposium of the Research Committee of The American Association of Petroleum Geologists at the 1960 annual meeting in Atlantic City, New Jersey. One paper presented in the General Session at that meeting, one reprinted paper, and three other solicited papers are also included.
The choice of “Geometry of Sandstone Bodies” as a timely and pertinent subject lor the 1960 symposium was made after an extensive canvass of Research Committee members and about fifty other geologists vitally interested in research in petroleum geology. From a group of about 15 proposed subjects, this one was selected as first choice by almost all those canvassed. Partly because of this high level of interest, the decision was made to attempt publication of the symposium as a special volume of The American Association of Petroleum Geologists. The word geometry in the title probably had several different meanings among the selectors, and for this reason an attempt was made to define the term adequately in order to establish uniformity of communication among symposium participants.
The dictionary definition of the word “geometry” is the science of magnitudes in space. In applying the term to the symposium theme, some modification and interpretation of its formal meaning were needed, and the following definition was therefore proposed for use in this volume—
Geometry of Sandstone Bodies—Spatial relationships of sandstone deposits within the sedimentary framework.
As used in this book, the subject is more than just a three-dimensional study in which thickness is added to areal distribution.