Drill stem test (dst):

The conventional method of formation testing.

The basic drill stem test tool consists of a packer or packers, valve or ports that may be opened and closed from the surface, and two or more pressure-recording devices.

The tool is lowered on the drill string to the zone to be tested.

The packer or packers are set to isolate the zone from the drilling fluid column.

The valves or ports are then opened to allow for formation flow while the recorders chart static pressures.

A sampling chamber traps dean formation fluids at the end of the test.

Analysis of the pressure charts is an important part of formation testing.