The objective of this study was to identify the descriptive tests for drilling stable holes through the problems of the selected formations. This study was performed on the shale samples taken from 10 wells in which hole instability was encountered to various extents during drilling the Germav formation. A total of 13 formation samples, characterizing the problematic intervals of the 10 wells under consideration, were evaluated. Descriptive tests were used to compare the samples and to determine the samples that should be used for drilling fluid selection tests. Based on the results of these tests it is possible to select the best drilling fluid for the formations studied. Descriptive tests include x-ray analysis, capillary suction time, hot rolling test, linear swelling test and cation exchange capacity test.