Samples of well cuttings are one of the chief sources of information concerning the formations of the subsurface in the Mid-Continent and Permian basin areas of the United States. By careful use in applying the methods of collecting and preparing these samples as described in this paper, it is possible to obtain cuttings samples which are truly representative of the formations penetrated. By microscopic examination of these samples, it is possible to prepare descriptions and plotted logs which give an accurate picture of the rocks penetrated. These logs can be correlated so as to reveal the stratigraphic conditions in the subsurface and trace time horizons through various facies variations of the subsurface formations. These time horizons can be used in the structural int rpretation of the region.

Detailed descriptions of cuttings samples from pay sections can be used, by methods outlined in this paper, in making estimates of oil and gas recovery from a field, in reservoir studies, and in guiding well remedial work.