What is a Drill Stem Test?

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  • Written By: Malcolm Tatum
  • Edited By: Bronwyn Harris
  • Last Modified Date: 07 January 2020
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Sometimes known as a DST, a drill stem test is a type of structured evaluation that makes it possible to determine the makeup of the geologic formation that is found adjacent to the drill pipe inserted into the ground during the extraction of natural gas or oil. In many cases, this type of test can help determine if drilling in the area is likely to produce the desired results, or if seeking another site would be more fruitful. It is also possible to use a drill stem test to determine if a site is suitable for digging for water as well as oil or natural gas.

First developed in the latter part of the 1920s, the actual equipment used in a drill stem test has evolved over time. Earlier methods involved using a small charge to create a perforation in a plastic casing that was lowered through the drill stem. When the charge was ignited, this created a small perforation in the casing that made it possible to collect samples of the surrounding fluids or earth. The sample was then retrieved and examined. In more recent years, the drill stem test has used technology that makes it possible to run small robots through the drill stem, collect a sample, and provide immediate feedback on the composition of the sample.


The results of a drill stem test make it possible to determine which sites are likely to yield enough product to make the digging commercially viable. By examining the sample collected from the test, it is possible to calculate the concentration of natural gas or oil that can reasonably be extracted. Should the results of the test indicate that the amount of product available falls below a certain range, the site is abandoned and other areas tested. This same general principal holds true when using a drill stem test to look for water. Should the sample not indicate the presence of an equitable amount of water within a certain distance from the surface, the site is abandoned in favor of another one that is likely to provide a more ample supply of water.

Depending on the type of equipment used to conduct the drill stem test, the process may take as long as 24 hours before the results are considered final. This is especially true when there is a need to also take readings that indicate the level of pressure at the site along with the availability of the product desired for extraction and eventual sale. Since tests of this type do often involve working with volatile materials, safety precautions that help to minimize danger for personnel working on the drill rig are common, with many nations setting specific regulations regarding the types of precautions that must be utilized during the testing.


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