Drill stem test
A drill stem test (DST) is a procedure for isolating and testing the pressure, permeability and productive capacity of a geological formation during the drilling of a well. The test is an important measurement of pressure behaviour at the drill stem and is a valuable way of obtaining information on the formation fluid and establishing whether a well has found a commercial hydrocarbon reservoir.
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History [edit]
Working in El Dorado, Arkansas, in the 1920s, E.C. Johnston and his brother M.O. Johnston developed the first drill stem tester and ran the first commercial drill stem test in 1926. In April 1929, the Johnston Formation Testing Corporation was granted a patent (U.S. Patent 1,709,940) and they subsequently refined the testing system in the early 1930s.[1]
In the 1950s, Schlumberger introduced a method for testing formations using wireline. The Schlumberger formation-testing tool, placed in operation in 1953, fired a shaped charge through a rubber pad that had been expanded in the hole until it was securely fixed in the hole at the depth required. Formation fluids flowed through the perforation and connecting tubing into a container housed inside the tool. When filled, the container was closed, sealing the fluid sample at the formation pressure. The tool was then brought to the surface, where the sample could be examined. In 1956, Schlumberger acquired Johnston Testers and continues to perform drill stem tests and wireline formation tests in both open and cased holes.
Procedure [edit]
During normal well drilling, drilling mud is pumped through the drill stem and out of the drill bit. In a drill stem test, the drill bit is removed and replaced with the DST tool and devices are inflated above and below the section to be tested.[2] These devices are known as packers and are used to make a seal between the borehole wall and the drill pipe, isolating the region of interest.[3] A valve is opened, reducing the pressure in the drill stem to surface pressure, causing fluid to flow out of the packed-off formation and up to the surface.
Results [edit]
In a low permeability or low pressure formation, surface production may not be achieved but the volume and flow rate of fluid can still be analysed within the drill stem.
See also [edit]
- TETRA Technologies. Inc.
- Northstar Drillstem Testers
- Drilling rig
- Horizontal Well Testing
- Oil well
- Schlumberger
Notes [edit]
- ^ History of Petroleum Engineering, API Division of Production, New York City, 1961, pages 561–566
- ^ "Society of Petrophysicists & Well Log Analysts glossary". Retrieved 12 September 2006.
- ^ "Society of Petrophysicists & Well Log Analysts glossary". Retrieved 12 September 2006.
External links [edit]
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