Shaly Sand Analysis
The basic formulas which make up shaly sand analysis are presented and discussed in this chapter. We begin by introducing methods for determining the volume of clay (Vd) in a reservoir. Once the amount of clay has been estimated, we use the volume of clay (Vcl) value to correct data from porosity logs and to calculate effective porosity (ϕe).
After identifying the methods used to find volume of clay (Vd) and effective porosity (ϕe), this chapter continues wifo log analysis procedures used to correct data from logs to yield the effective water saturation (Swe) of shaly sands. Water saturation formulas are organized around log suites, since the available log package largely dictates which formulas must be used to find the effective (as opposed to total) water saturation. Our reader may need to choose a technique based on either the date of a log or by log suite depending on available information. Time divisions are presented in the text not as an exercise in the history of logging, but rather as a practical guide for rapid identification of the strategies needed to evaluate a particular log.
Time is subdivided by the early 1950s, the late '50s, and the 1960s, 1970s, and 1980s. The reader need only find his or her log dates, check them against the historical breakdown presented here, and against log type, and then use the formulas suggested by the text to find effective water saturation
We conclude our discussion in this chapter with some helpful guidelines that are
Figures & Tables
The intent of this publication is to provide the reader with a simplified review of shaly sand well log analysis. Because of the important effects that shale or clay have on both reservoir quality and well log response, a working knowledge of the subject provides a necessary basis for accurate log analysis. Techniques illustrated in the text will assist in making better decisions about the productive potential of shaly reservoirs and in mapping shaly sandstones. This book is intended as a quick look, ready reference guide.