Drill Stem Testing Drill Stem Testing (DST) is a critical procedure in oil and gas exploration used to evaluate the productive capacity, pressure, and permeability of a geological formation while drilling. The test is conducted by lowering a tool into the welbore that temporarily isolates a section Dyn the formation. This allows reservoir fluids--such as oil, gas, or water-to flow into the drill stem under controlled conditions without completing the well. Data collected from DST, including flow