Selected drill-stem test data for the Upper Colorado River basin

Permeability data from aquifers and confining layers may be available from drill-stem tests made during the course of petroleum exploration. During the drill-stem test, the stratigraphic interval of interest is isolated in the hole by the use of packers attached to the drill string. Fluid flows into the drilling pipe under the influence of the formation head. Pressure measurements and other data collected during the course of the test are used to gain information on undisturbed formation head, permeability, hydraulic conductivity, and fluid temperature. Drill-stem test data for individual formation in the Upper Colorado River Basin presented in tables in this report are arranged in groups of 10 hydrogeologic units that were classified on the basis of geologic age, location, depositional environment and lithology. Maps indicating the locations of test sites and areal distribution of test data within the 10 units are provided at the beginning of each table. Stratigraphic columns also are provided to identify the relative ages of the formation tested and to correlate regional hydrogeologic units. (USGS)