Since 1980 Northstar has been setting the standard in drill stem testing (DST) around the world.  With global operations in over 15 countries, Northstar specializes in drill stem testing: field services, manufacturing, tool engineering and innovation.  With over 30 years of DST service history, we have the experience to support global onshore, offshore and remote well testing operations.

About Drill Stem Testing

Drill stem testing is an oil and gas exploration procedure to isolate, stimulate and flow a downhole formation to determine the fluids present and the rate at which they can be produced.  The main objective of a DST is to evaluate the commercial viability of a zones economic potential by identifying productive capacity, pressure, permeability or extent of an oil or gas reservoir.  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 bottom hole 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. In addition to packers a downhole valve is used to open and close the formation to measure reservoir characteristics such as pressure and temperature which are charted on downhole recorders within the BHA. Below are two types of BHA DST, Cased Hole which can be applied after the well has been cased, and Open Hole which may be performed before casing.

Applications of drill stem testing:

Cased Hole

Performed after the well is cased, cased hole drill stem testing uses a retrievable production packer that is set above the zone of interest. The well is then flow tested through perforations in the casing. The two types of cased hole testing are pressure operated and mechanically operated.

Open Hole

Because it's performed before casing is run, open hole drill stem testing can be the most economical way to determine productive capacity, pressure, permeability or the extent of an oil or gas reservoir. The testing equipment is run into the well and the zone of interest is isolated using inflate or compression-set packers, depending on your requirements and drilling conditions.

Alternate Procedures

Depending on testing objectives and scope of work, drill stem testing may also be performed in combination with various other exploration and completion processes such as fluid loss control and well control, closed chamber tests, well stimulation and a combination of DST and TCP.