 These tests can be performed in both open and cased hole environments and provide exploration teams with valuable information about the nature of the reservoir.Drill stem testing involves deploying a series of tools known as a test bottomhole assembly (BHA).A basic drill stem test BHA consist of a packer or packers, which act as an expanding plug to be used to isolate sections of the well for the testing process, valves that may be opened or closed from the surface during the test, and recorders used to document pressure during the test.