Serving oil, gas, mining and heavy industry in Africa and beyond


Rapid, low-risk and cost-effective well testing services

Regis Head Office | Mauritius
Tel: +(230) 483 4700

How Drillstem testing works


Acquired by Regis Holdings in 2013, DST Australia Ltd performs Australia-wide on-shore drillstem testing with great success. Regis founded DST International Ltd in 2015 to provide drillstem testing (DST) services in other regions, most recently achieving impressive results in Mozambique. 

DST International is rolling out drillstem testing services to all of Regis' areas of operations. These services include:

  • Open-hole conventional straddle and bottom hole
  • Open-hole inflate straddle and bottom hole
  • Cased-hole
  • Conventional coring
  • Slimhole conventional straddle and bottom hole
  • Closed chamber testing
  • Diagnostic fracture injectivity testing
  • Injection fall-off testing
  • Real-time well data by telemetry

Drillstem Testing

Drillstem testing is a valuable tool in the oil and natural gas extraction process.
It is a procedure to determine the productive capacity, pressure, permeability or extent of an oil or gas reservoir. Drillstem testing is essentially a flow test performed on isolated formations to determine the fluids present and the rate at which they can be produced. By employing parts such as a Bottom Hole Assembly (BHA), application tests can be done to determine the viability and commercial productivity of a well within an accelerated time line as well providing lower financial risk compared to conventional well testing methods.

A basic drillstem BHA consists of a packer (or packers), which acts 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 down-hole valve is used to open and close the formation to measure reservoir characteristics such as pressure and temperature that are charted on down-hole recorders within the BHA.

Applications of drillstem testing:

Drillstem testing can be performed in both open- and cased-hole wells:

  • Open-hole
    Because it's performed before casing is run, open-hole drillstem testing can be the most economical way to determine the productivity of an oil or gas reservoir. The testing equipment is run into the well and the zone of interest is isolated using inflate or conventional set packers, depending on your requirements and drilling conditions.
  • Cased-hole
    Performed after a well is cased, drillstem testing uses the same technology as testing in open-hole wells. Cased-hole testing is the most economical way of re-evaluating old wells or retrieving data from new wells where casing has had to be run due to poor well conditions. Both inflate and conventional DST tools can be run in-hole to isolate perforations in casing to retrieve well data.
  • Inflate
    Open-hole inflate tests utilise a pair of interval-spaced packers which are inflated using annular fluid to isolate the formation of interest. This type of testing is adaptable to a wide range of conditions. Inflate testing is the most time- and cost-effective method that can be used to isolate multiple formations since multiple zones can be analysed during a single run in-hole.
  • Conventional
    Open-hole compression, or a conventional drillstem test, uses a compression-set packer set above the formation, with tail pipe below the packers to the bottom of the hole. Placing weight on the tool string opens the hydraulic valve allowing the formation to flow into the tool and rise to the surface.
    The formation is flowed for a specified time period, after which a shut-in valve is rotated to the closed position for a specified shut-in period.
  • DST Web Viewer Live!
    This proprietary system shortens decision times and reduces rig costs by providing real-time data analysis and direct communication between the office and the field. DST Web Viewer Live! enables clients to remotely and securely access real-time test results from multiple stations anywhere in the world via satellite link-up. Using DST Web Viewer Live!, a DST technician can provide guidance while the tests are being run, and decision makers can communicate securely with the field in the event of a tight hole. They can see the data as it is collected, analyse it and amend the test parameters to ensure optimal data collection.

To learn more about DST Australia and their services please click here: