Drill Stem Test (DST)
Definition - What does Drill Stem Test (DST) mean?
A Drill stem test (DST) is a systematic procedure for evaluating the hydrocarbon potential of a reservoir. The test is a valuable and cost effective test that is mainly employed in exploratory wells. The main objective of the test is to study the reservoir characteristics as well as evaluate the commercial aspects of the reservoir.
Petropedia explains Drill Stem Test (DST)
A Drill Stem Test is a test which is carried out in a wellbore to determine its potential. The following are the set of tools used in the test:
- Packers having expandable seals that isolate the formation.
- Downhole valves that open and close the well for reservoir build up studies during flow. These valves are also closed during emergency situations.
- A data recorder that collects the pressure and temperature data during the testing period.
- Sample catchers that collect the sample near the wellbore at the existing conditions.
These tools are run over drill string or tubing string to certain depth and the zone of study is isolated by setting the packers nearer to the zone. These packer elements seal the zone from the rest of the wellbore which allows the hydrocarbons to flow inside the tubing string to the surface. DST can be carried out in an open hole as well as in a cased hole; however, in a cased hole the bottomhole assembly has perforating guns along with the above tools.
The data obtained from the test includes fluid samples, flow rates of the formation fluids, reservoir pressure and temperature, permeability and other formation properties. DST is a feasible method in evaluating the reservoir characteristics as well as to estimate the life of the reservoir in turn the economical aspects.